Petrel 2010 Reservoir Engineering Course

Reservoir Engineering Course

Petrel 2010

About Petrel* Development on Petrel seismic-to-simulation software began in 1996 in an attempt to combat the growing trend of increasingly specialized geoscientists working in increasing isolation. The result was an integrated workflow tool that allows E&P companies to think critically and creatively about their reservoir modeling procedures and enables specialized geoscientists to work together seamlessly. With the enhanced geophysical tools and the integration of ECLIPSE* reservoir simulation software and streamline simulation, Petrel is now a complete seismic-to-simulation application for • 3D visualization

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3D mapping 3D and 2D seismic interpretation well correlation 3D grid design for geology and reservoir simulation depth conversion 3D reservoir modeling 3D well design upscaling volume calculation plotting post processing streamline simulation ECLIPSE

Copyright Notice © 2010 Schlumberger. All rights reserved. No part of this manual may be reproduced, stored in a retrieval system, or translated in any form or by any means, electronic or mechanical, including photocopying and recording, without the prior written permission of Schlumberger Information Solutions, 5599 San Felipe, Suite 1700, Houston, TX 77056-2722.

Disclaimer Use of this product is governed by the License Agreement. Schlumberger makes no warranties, express, implied, or statutory, with respect to the product described herein and disclaims without limitation any warranties of merchantability or fitness for a particular purpose. Schlumberger reserves the right to revise the information in this manual at any time without notice.

Trademark Information *Mark of Schlumberger. Certain other products and product names are trademarks or registered trademarks of their respective companies or organizations.

Table of Contents About Petrel* ...........................................................................2 Copyright Notice........................................................................3 Disclaimer..................................................................................3 Trademark Information..............................................................3 Module 1 - Introduction...........................................................11 Prerequisites............................................................................11 Learning Objectives.................................................................11 What you will need.................................................................12 What to expect........................................................................12 Icons........................................................................................13 Terminology.............................................................................14 Workflow diagram...................................................................19 Agenda....................................................................................19 One application, seismic to simulation...................................20 Module 2 - The Petrel User Interface...................................23 Introduction.............................................................................23 Lesson 1 – The Petrel user interface......................................24 The Petrel user interface.........................................................25 Starting Petrel.........................................................................40 Petrel Interface........................................................................41 Display window.......................................................................42 Object settings........................................................................43 Lesson 2 – Making a simple grid with simulation fault.........47 Exercises - Making a simple grid a with simulation fault......59 Making a simple grid...............................................................59 Summary..................................................................................64 Module 3 - Functions...............................................................65 Introduction.............................................................................65 Lesson 1 - Make fluid model...................................................66 Exercises - Make fluid model..................................................81 Make a black oil model from correlations..............................81 Reviewing fluid model settings...............................................83 Import a keyword fluid model..................................................83 Plotting the fluid model...........................................................83 Create multiple viewports – Optional.....................................85 Reservoir Engineering

Table of Contents • 5

Lesson 2 - Make rock physics functions.................................88 Rock compaction function.......................................................89 Saturation function..................................................................91 Capillary pressure....................................................................95 Exercises – Make rock physics functions...............................98 Make a saturation function.....................................................98 Make a rock compaction function.........................................100 Reviewing rock physics functions data.................................102 Import a keyword rock physics function................................104 Summary................................................................................105 Module 4 - Initialize the Model and View 3D Properties.................................................................................107 Introduction...........................................................................107 Lesson 1 – Initialization of the model...................................108 Introduction...........................................................................108 Exercises – Initialization of the model..................................120 Exercise Workflow.................................................................120 Exercise Data.........................................................................120 Initialize model......................................................................120 Lesson 2 – 3D Viewing..........................................................123 Exercises – Results viewing..................................................129 3D viewing.............................................................................129 Making filters using a Histogram window............................131 View data on an intersection plane......................................133 Optional Exercise - The multi-value probe............................134 Summary................................................................................135 Module 5 - Upscaling.............................................................137 Introduction...........................................................................137 Lesson 1 – Grid Coarsening using the Pillar gridding process..................................................................................138 Pillar Gridding - Concept.......................................................140 Pillar Gridding - Terminology.................................................141 Exercises – Grid coarsening..................................................148 Grid coarsening using the Pillar gridding process................148 Changing the grid orientation...............................................151 Lesson 2 – Vertical coarsening –the Scale up structure process..................................................................................153 Exercises – Vertical coarsening and grid quality check........159 6 • Table of Contents

Reservoir Engineering

The Scale up structure process.............................................159 Grid quality check..................................................................160 Using value filter...................................................................162 Averaging methods...............................................................167 Directional averaging methods for permeability..................169 Exercises – Scale up properties............................................170 Exercise Workflow.................................................................171 Exercise Data.........................................................................171 Scale up properties...............................................................171 Apply different methods........................................................173 Review the upscaled properties............................................174 Review upscaled properties in a 3D window.......................175 Summary................................................................................177 Module 6 - Local grid refinements and Aquifers..............179 Introduction...........................................................................179 Lesson 1– Local grid refinements.........................................180 Exercises– Local grid refinements........................................190 Import a polygon....................................................................190 Make a local grid set.............................................................190 Inspect the local grid set.......................................................192 Upscale property – Optional.................................................193 Lesson 2 – Aquifers...............................................................195 Exercises – Aquifers..............................................................202 Add an aquifer.......................................................................203 Summary................................................................................206 Module 7 - History development strategies......................207 Introduction...........................................................................207 Lesson 1 – History development strategies..........................208 Exercises - Make a history development strategy................217 Import observed data............................................................217 Make a history development strategy..................................220 View the development strategy data....................................221 Add a rule to limit the production pressures........................222 Define and run simulation cases...........................................223 Exercise: Change the line style in function windows...........236 Plot window...........................................................................238 Summary data in a 3D window - Optional............................240 View data on streamlines - Optional....................................241 Reservoir Engineering


Lesson 3 (Optional) – History match analysis......................242 Exercises – History match analysis.......................................256 Run history match analysis...................................................256 View match data in a map window......................................257 View match data in a function window................................259 Compare cases in a Map window.........................................260 Summary................................................................................262 Module 8 - Well Engineering...............................................263 Introduction...........................................................................263 Lesson 1 – Import and Design Well Paths............................264 Well path design...................................................................267 Simple vertical well...............................................................268 Exercises – Import well data and design well paths............276 Import well data....................................................................276 Make a vertical well..............................................................278 Setting up the 3D window....................................................279 Well path design...................................................................282 Reference project tool...........................................................285 Lesson 2(Optional) – Automatic well placement..................286 Create best fit well................................................................286 Laterals design......................................................................288 Exercises – Automatic well placement - optional................291 Lesson 3 – Results, reports and quality checking.................295 Well manager and saved searches.......................................303 Well tops and well report.....................................................304 Lesson 5 – Well completion design......................................306 Exercises – Well completion design.....................................322 Import well completion events..............................................328 Make completions using the Operations tab........................331 Summary................................................................................334 Module 9 - Prediction strategies.........................................335 Introduction...........................................................................335 Lesson 1 - Prediction development strategy.........................336 Exercises – Prediction strategies..........................................347 Use a default strategy...........................................................347 Add a new rule to an existing strategy.................................349 Define a prediction case........................................................350 View simulation results.........................................................351 8 • Table of Contents


Make a strategy with a tabular rule - Optional....................352 Lesson 2 – Keyword editor....................................................355 Import existing simulation case............................................363 Examples of use of the Keyword editor................................367 Exercises –Keyword editor - import a case..........................368 Load a simulation case ........................................................369 Edit the case..........................................................................370 Run the simulation case........................................................371 Convert to Petrel case...........................................................372 Summary................................................................................373 Appendix 1 - Advanced Workflows....................................375 Dual porosity – Dual permeability........................................375 Sector modeling....................................................................377 Hysteresis..............................................................................380 Remote job submission.........................................................382 Index.........................................................................................383



Module 1 - Introduction The purpose of this course is to introduce you to the reservoir engineering tools in Petrel. In this course, you will create a simple simulation grid and upscale a geological grid. You will learn how to create black oil fluid tables and rock physics functions in Petrel. In addition, you will import and design wells and add completion items. Finally, you will combine it all and submit it for simulation before viewing results inside Petrel. Traditionally, the engineer had to employ a range of different software tools, hence, data had to be exported/imported between the different applications. Also, feedback to the geological model used to be difficult to implement. The vision for Petrel RE is to make all of these tools available from the Petrel user interface.

Prerequisites To successfully complete this course, the user must have knowledge of the following: • English proficiency • Basic Windows and practical computing skills • Familiarity with reservoir engineering fundamentals

Learning Objectives In this course, you will prepare black oil simulation cases for ECLIPSE* and FrontSim* using Petrel. You will learn: • About the Petrel user interface • How to build a simulation grid • How to scale up structure and properties • How to use the correlation library to make black oil fluid tables and rock physics functions • How to use the well engineering tools in Petrel • How to set up simulation cases and view the results Reservoir Engineering

Introduction • 11

What you will need

In this course, you will need the following hardware and applications in order to perform the workflow: • A personal computer with a minimum of 2GB of RAM; however, we recommend 16GB of RAM for optimal performance. • For Petrel 32-bit: Microsoft XP 32. For Petrel 64-bit: Vista 64 and XP 64. • A graphic card compatible with Petrel • A Petrel license and license key • Petrel Seismic to Simulation Software with the latest updates • Training datasets

What to expect In this training material, you will encounter the following: • Overview of each module • Prerequisites to the module (if necessary) • Learning objectives • A workflow component • Lesson(s) • Scenario-based exercises • You will also encounter notes, tips and best practices

12 • Introduction


Icons Throughout this manual, you will find icons in the margin representing various kinds of information. These icons serve as at-a-glance reminders of their associated text. See below for descriptions of what each icon means.

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Introduction • 13

Terminology Petrel introduces new terms and expressions. Some of the most frequently used in this manual are briefly explained below. 3D Grid - A network of horizontal and vertical lines used to describe a three dimensional geological model. Petrel uses the “Corner Point 3D Grid” technique. Boundary for the Pillar grid – Defines the extent of the model. You can use a polygon as input, or you can digitize the boundary. Faults can be set as part of the boundary. Cases pane - Shows volumetric cases and simulations cases as set up in the “Define simulation case” process. Cell - The smallest volumetric element in the Pillar grid. Each cell has a unique I, J, K position in the Pillar Grid. I, J, K positions are zero based integer locations of cells in a grid. It uses a left-handed orientation I, J being a horizontal surface and with K increasing downward. The grid has a number of cells equal to the number of I times the number of J times the number of K points. I, J, K indexing provides a way of identifying a cells position in the grid. Contact level - The level of a Gas-Oil contact or an Oil-Water contact, normally at a constant depth but a tilted contact can be represented by a surface. Corner point grid - A flexible grid structure where the eight corners of a cell (the nodes) can be moved to form irregular cell geometries. Directions (in the Pillar gridding process) – User defined guidance for orientation of cells along faults. A fault can be given a direction in which case the grid is enforced to be aligned with that fault. Fault - Vertical surface that segments the Pillar grid. It is represented by a set of pillars that join together to define the fault. An area enclosed by faults will, by default, make out a segment of the model. A fault can be given a direction in which case the grid is enforced to be aligned with that fault. Filter – Petrel can display the whole model (all elements) or selected parts of it. Powerful filter techniques enable the user to take full control of the 3D grid and visualize only the elements of interest for quality control. Filters in Petrel are used both for visualization and for 14 • Introduction


calculations. There are two basic types of filters in Petrel. The first type is a simple On/Off type, where an element is either turned on or off. Other filters are more advanced (for example filtering of properties) and are based on values set by the user. Function bar - Also called tool bar (in Microsoft terminology). This is a group of icons on a horizontal or vertical bar. Only icons that can be used with the current active process is displayed in the function bar. Function window - Plot window used to display functions, cross plots, sample variograms and variogram models. Histogram window - Plot window used for display of histograms and cumulative distribution functions. Horizon - The equivalent of a surface, except that a horizon is a surface in a 3D grid and an integrated part of the 3D model. A horizon in a Petrel 3D grid can have multiple Z values at a single XY value whereas a surface can not. Input pane - imported data such as lines, wells, fluid models, gridded surfaces and SEG-Y data is stored here. Also data created by Petrel process like: Development strategy, Rock physics functions, etc. Intersection - A cut through a three dimensional model (3D grid). Intersections can be plane surfaces with arbitrary direction and dip, but can also be cross sections along one of the main directions of a 3D grid (I, J, K directions). Intersection window - Plot window used for generation of scaled plots of cross sections. Editor - Allows you to use all functionality of ECLIPSE and FrontSim, which can not be accessed through the Petrel user interface. Layers - Fine scale division of 3D grid, which defines the cell thickness. LGR - Local grid refinement; allows for a finer resolution of the grid in demanding areas. Local grids are defined using wells, surfaces and polygons as input. Map window - Plot window used for generation of scaled plots (2D maps), and for display of history match values and variogram maps created in Petrel. Menu bar - Special tool bar at the top of the screen that contains Reservoir Engineering

Introduction • 15

menus such as File, Edit, and View. Model - Complete set of data needed to describe a three dimensional geological model. This includes the 3D grid structure with faults and horizons, and all cells with different properties. Each project can contain several models and each model can contain several 3D grids. Models pane - data connected with a 3D model (such as faults, trends and 3D grids) is stored here. Velocity models and discrete fracture network models are also stored here. Nodes - In a 3D grid, nodes are corner points of the grid cell. In a 2D grid they are intersection points between grid lines. Pillar gridding - The process of creating the three-dimensional (3D) grid. With this process you make the framework of the 3D grid using a combination of key pillars, trend lines and a boundary. The result is a three dimensional framework called a skeleton grid. Pillars – Vertical lines connecting the corner points of 3D grid cells. The shape can be any of the four standards: vertical, straight, listric or curved. There are two basic types of pillars in a 3D grid: faulted and non-faulted. After the pillar gridding process, the key pillars are replaced with faulted pillars. Non-faulted pillars are inserted in the nonfaulted area of the 3D grid. Polygon - Polygons made in Petrel can be used for many different purposes. Like digitize contours for structure maps, isochores or properties. Boundary polygons are used in the “Make surface” process, or as a boundary in the “Pillar gridding” process or the Make aquifer process. Processes pane - All the processes that you can apply to you data is located here. For each Process a new set of tools is available in the Function bar. Results pane - the numerical results of volume calculations and simulations are stored in this pane, such that they can be visualized and any reports made. Also Observed data for Development strategy is stored here. Segments (Regions) – Segment in Petrel is an area that is closed by faults, grid boundary, segment boundaries or any combination of these. Segment is similar to the term “Regions” used in ECLIPSE. 16 • Introduction


Simulation grid - The 3D grid that will be used for flow simulation in Petrel or exported to other simulation packages. This grid is usually a coarser, upscaled version of the geological grid. Skeleton – Three 2D grids representing the top middle and base points of the Key pillars in a pillar grid. These are used to quality check the pillars and therefore the 3D grid. The skeleton is not related to horizons in the grid in any way. Status bar - Information on processes, coordinates, etc. in the rightbottom corner of the user interface. Surfaces - 2D grids (imported or generated in Petrel). A surface is a simpler version of a horizon in Petrel, the major difference being that horizons are held in 3D grids (as opposed to 2D grids) and can therefore have multiple Z values at each XY point. Surfaces are stored in the Input pane, while horizons are stored in the Models pane. Templates - Are linked to objects in Petrel and control globally their settings for color, units, measurements etc. Petrel comes with several predefined templates: depth and thickness color tables, property templates and seismic color tables. Templates pane - color tables and all the different templates are stored under this pane. Title bar - The file name (project name) and location is displayed in the Title bar on top of the user interface. Tool bar - Icons for commonly accessed commands in the user interface. These tools are useful shortcuts for items that also can be found by accessing the menu bar. Transmissibility multiplier – The transmissibility is a number assigned to cell faces that describes the ability for a fluid to flow from one cell to another. A transmissibility multiplier can be assigned to faults to change the ability for a fluid to flow past the fault. Trends (in the Pillar gridding process)– User defined guidance for the grid cells orientation in a particular direction (I- and J-directions). Also segment divider (when no faults). Weighting – Used in several processes to increase or decrease the importance of some of the data in a computation. For example, in the Scale up properties process one can decrease the influence of property Reservoir Engineering

Introduction • 17

values from cells with a tiny volume when populating the coarse grid by using the Volume weighting option. Well tops – Intersection points between well trajectories and structural surfaces. Sometimes called well points, well picks or tie points. Well trajectories - Lines in space representing well paths. Well section window - Plot window used for display of well sections used in the Well correlation and the Well completion design processes. Windows pane - stores all opened and active plots and windows used in the Petrel project. In addition it holds the Light sources and the Cursor tracker. Workflows pane - stores workflows made using the Workflow editor and/or the Uncertainty and optimization process. In addition it holds a folder with predefined variables. Zones - A zone is defined by the volume between a top and a bottom horizon.

18 • Introduction


Workflow diagram

Agenda


Introduction • 19

One application, seismic to simulation

Usability Petrel 2010

Familiar windows style

Tools from seismic to simulation

20 • Introduction


Traditionally, the geoscientists provided input to the reservoir simulation model. Since Petrel provides one tool for the entire workflow, it is easier for the different professionals to work in an interrelated way. The building and maintaining of a simulation model is an iterative process. As the tools for modeling and simulation are available in one single application, it is easier for the engineer and the geologist to cooperate.

The engineer used to depend on a number of software products in order to set up, run and view the results of a simulation. Petrel now provides one common user interface for workflows from seismic interpretation to reservoir simulation.


Introduction • 21

The vision of Petrel is to incorporate all of those tools into one common user interface to avoid challenges and time spent on import/export. Most of the major workflows in ECLIPSE Office, Schedule, FloGrid, and FloViz can be accomplished in Petrel 2010.1, but there are still some gaps. The main gaps are: • FloGrid – Petrel has no unstructured grids; no upgridding (the workflow to determine where to put the layers based on property distribution). • Schedule – On import, Petrel extracts data from the WELSPECS and COMPDAT keywords together with dates. But it will not make any Development strategies. In Petrel, layer shifting is accomplished by correcting the grid to match the well tops, rather than moving perforations to match a bad grid. • Compositional fluid properties – Petrel offers functionality to make compositional and thermal PVT models. However, the equation of state (EOS) of such models cannot be tuned to the laboratory experiments.

22 • Introduction


Module 2 - The Petrel User Interface Introduction In this module, you will become familiar with the Petrel user interface. You will also learn how to make a grid using the Make simple grid process. This is a process that can be used to make grids for nonfaulted reservoirs. However, it is possible to insert a “simulation fault” into the grid to model the effect of a (partially) sealing fault. Prerequisites • There are no prerequisites for this module Learning Objectives In this module, you will learn how to: • Start Petrel with a new or an existing project • Navigate in the user interface • Review and alter settings for Petrel objects • Display data in 2D, 3D, and function windows • Make a simple grid for a non-faulted reservoir • Insert a simulation fault into the simple grid


The Petrel User Interface • 23

Lesson 1 – The Petrel user interface

Petrel RE for newcomers Menus

24 • The Petrel User Interface

Settings

Visualization

File management


User interface Menu bar Tool bar

Function bar

Petrel explorer panes

Display window

Status bar

Object information

The Petrel user interface The Petrel user interface consists of two main windows, the display window and the Petrel explorer panes: Petrel explorer panes: There are eight panes available in Petrel and they can be put in two separate explorer windows (default). All panes have free placement and grouping, and can be enabled or disabled from the View option in the Menu bar. The Input pane contains all data that is not defined as part of a 3D grid or a fault model. The Models pane contains all fault models and 3D grids with grid properties. The Templates pane contains predefined templates, while the Results pane is a filter for simulation and volumetric results. The Processes pane contains a list of the available processes in Petrel in the order which they are usually performed. The Workflows pane contains workflows created by the Workflow editor or the Reservoir Engineering


Uncertainty and Optimization process. The Cases pane stores all simulation and volumetric cases and the Windows pane stores all windows (3D window, interpretation window etc.). • Toolbar: General tools related to import and visualization • Menu bar: Familiar Windows menus, such as File > Open, Edit > Copy, File > Save, Help > Manual. • Function bar: Tools related to the selected process in the Processes pane. • Object Information: When clicking on an object in the display window, information about it will appear in the lower right corner. • Status bar: Shows the status of the last performed action.

Input and Model panes Input pane Contains all imported data and all subjects that are not a part of the 3D grid. Models pane Contains all Fault models and 3D grids. Bold item Click on an object name to make it active.

Input and Model panes Bold Item: Note that the name of the active item is printed in a bold font. It is the active item that Petrel will use in a process. For instance, if you want to use the Top Tarbert data as input for making a surface, select it by clicking on it, it becomes bold and Petrel recognizes this as the object to use and you know which item is active. 26 • The Petrel User Interface


+/- Sign: Data is stored in folders within the Petrel explorer panes. The folders are expanded by clicking on the plus sign and collapsed by clicking on the minus sign in front of it.

Cases and Results panes

Cases pane A new case is added each time a simulation or volume case is defined. Results pane Used to select lines to view in function windows. Used to display 3D properties in 3D window.

Cases and Results panes When a simulation case is defined, it is stored on the Cases pane. The check box in front of the case is used to select to view results from that particular case. You can plot line vectors (rates, pressures, etc.) in a function window by specifying which data to view on the Results pane. The simulation grid results (Static and Dynamic grid properties computed by the simulator) are also stored on the Results pane. To visualize it, you can use 3D or 2D window. Use the time player to see how the properties change during simulation time.



Processes pane Function bar

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1. Active Process A process needs to be active (bold) to be used. 2. Function Bar Shows available tools for the selected process.

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Only one process can be active at the time.

Processes pane and Function bar The Processes pane contains a list of all available processes in Petrel. If a process is available, the process name will be colored black. If a process is not available, it will be grayed out and you cannot select it. There are various reasons why a process may not be available. The most common reason is that a previously required process has not been completed. For example, you don’t have access to property modeling before you’ve defined horizons. Another reason is licensing. A red prohibition sign indicates that your license configuration does not contain that process. The Function bar is located on the right hand side of the screen and contains the icons/tools available for the current active process within the Processes pane. The available tools are active and in color, this will help you to know which tools to use for each process.



Workflow editor and the Uncertainty and optimization process: The Workflows pane stores workflows created by the Workflow editor and the Uncertainty and optimization process. Workflows provide a programming-like user interface to Petrel. They allow for automating tasks such as plotting or sensitivity studies. New workflows are initiated from the Insert option in the Menu bar. Uncertainty, proxy, and optimization workflows are made using the Uncertainty and optimization process which is stored in the Utilities folder of the Processes pane. Windows pane All visualization windows in a project are stored on this pane. Even if you exit a window, it will still be stored in the Windows pane. Use the Windows pane to organize windows. You can, for example, delete windows and rename windows for quick access. When plotting the oil production rate, rename the Function window to Field oil production to better distinguish it. A checked box in front of a window indicates an “open” window. Having many open windows can slow down performance, thus, it is recommended you keep the number of open windows to a minimum. Each window is stored as a folder in the Windows pane. In this folder, icons are stored which are used for visualizing legend, axis, setting background color, etc. Those tools are also found in the toolbar. Reservoir Engineering


Coordinate systems

Petrel offers the possibility to do cartographic transformations of data on export and import. With 2010, only some data types are supported, mainly lattice data such as 3D seismic. Select Null to disable this functionality.

Petrel 2010.1 is the first release that offers the possibility of doing cartographic transforms and conversions on import and export. Well data is supported, but not 3D grids, hence, it is not yet fully functional for reservoir engineering purposes. Select Null, to disable the functionality and to make Petrel perform like pre-Petrel 2010.1.



Project settings and units

Units Select a Unit system from the dropdown menu (e.g. Metric or Field), or select Customize to set units from a mixed unit system.

Note: There is NO unit conversion inside Petrel; it has to be done on import.

Project settings Petrel will allow for a mix of different units to be imported into the project. A typical example is to have well data and production data in feet, and maps and other data derived from seismic in meters. You must check to ensure that the data is imported with the correct units. It is not possible to convert units of data already imported into the project, but data can be converted on import and export. The best workflow to ensure common units in a Petrel project is: 1. Check your data before import and decide which units are best to use as your project units. Petrel will allow you to use local coordinates, field, metric or a combination, which most commonly are UTM coordinates in the XY-direction and feet in the Z-direction. 2. When creating a new Petrel project, open the Project settings as described on the slide and select the unit system you want to use in your project. Reservoir Engineering


3. For every object you import, check the file before import to inspect the units of the data. Then, select to apply unit conversion in the import dialog, if needed. 4. If you discover that the unit of a data object is inconsistent with the other data in the project, delete it and re-import it with the correct conversion. When importing data from ECLIPSE keywords, Petrel is looking for METRIC or FIELD keywords in the file. If none of this is specified then it will assume that the data in the import file is in the same unit system as Petrel project. If it is specified, and the units of the file you import is different from the units in the project, then the data will be converted on import. Also note that Petrel has two different concepts of time units; namely depth measured as two way traveling time for the seismic waves in addition to the usual meaning of time.

Object Settings 1. Every object has a settings window 2. Access settings

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Object settings To access the settings dialog for objects in Petrel, right-click on the object and choose Settings, or double-click the object. The Settings dialog provides information about the object and whether it is possible to alter the objects. The tabs vary by the object type.

Object Settings Style tab

Most objects have a Style tab. Possible to adjust display parameters.

Style tab The Settings dialog contains different tabs and information. Depending on the type of object, additional tabs will be added for more functionality. However, the settings will always include an Info tab and a Statistics tab. The Style tab is only active when a display window related to the Style options is active (for example, 2D vs. 3D display windows).



Object Settings Info Tab

1. Rename objects by entering a new name. 2. The Template can be changed.

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3. The Comments tab is empty by default; designed for user input.

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4. The History tab keeps track of the main events related to the object (e.g. operations, dates etc.).

Info tab On the Info tab, you can rename the object and change the template. The Comments tab is a white, editable area where you can add any information such as the source of the data that was imported and its reliability. The history of the object is stored on the History tab, including information about edits and operations performed on the object. By right-clicking in this field, you can add your own date stamped comments or clear the history completely. Note that not all objects have a History tab.



Object Settings Statistics Tab

The content of each item can be checked under the Statistics tab. The zones can be viewed separately.

Lists The first list gives the X, Y, Z coordinates. If an attribute is available it will also be shown. One or all lists can be copied to an output sheet. Toggle on one of the lists (e.g. List 1) and click the output icon. The contents of the list will be written to an output window.

Statistics tab It is important to quality check (QC) the statistics for accuracy to verify that the items hold the correct values. By default, ‘Z’ values are negative based on a reservoir being below sea level. If your data is above sea level, select the appropriate options when importing your data. Remember that this is opposite from GeoFrame which works in positive ‘Z’ values. It is possible to generate a report from the statistics table: Click on the Copy to output sheet button. A report will be generated and it can be saved to file or copied and pasted into Excel.



Visualization Windows

Visualization windows A range of different types of windows are available: • 3D window – for visualization of data in 3D. • 2D window – for visualization of data in 2D. This is useful when working with polygons, and when you want to be certain that you are viewing from above. • Map window – Used for plotting horizons and layers of the 3D property. • Intersection window – plotting window for intersections. • Interpretation window – 2D window used for seismic interpretation. • Histogram window – used for plotting histograms. • Function window – used for plotting cross plots, variogram, and line plots. • Stereonet window – used for displaying dip and azimuth data. 36 • The Petrel User Interface


• Well section window – used for well correlation, interpreting logs, and defining well bore completions. • Plot window – Multiple viewports can be inserted (for example, function, intersection, and histograms together). A viewport is a limited rectangular area where data objects are displayed. • Tornado plot window – to display an organized overview of analysis results.

Visualization Display tools

Maneuvering from Function bar

Visualization from Tool bar

Move – Left mouse button View all displayed data Select/Pick mode – Allows for selecting objects and getting information about them (in the status bar)

View from specified position Target zoom

To move the view in any of the windows, use the left mouse button. However, to be able to move anything, you must have the View mode (hand) active. When the View mode is active, a hand is shown instead of the mouse pointer. The Select/pick mode (arrow) is used to select an item. When in this mode, you can click on any object and get information about it in Petrel’s lower right corner. Reservoir Engineering


Note that all windows that show a vertical scale can be set to show data in either TWT (two way time) or TVD (true vertical depth). The default is Any, which means that data from different domains can be mixed in the windows (for example, useful for checking whether the wells are intersecting with the seismic data cube). However, if the vertical scale of a window is set to TWT, it is not possible to view depth data in the window. If you ever have trouble visualizing data in the selected window, always check that the vertical scale of the window is set to TVD (or Any).

Visualization Check boxes

Gray, square boxes – select the check box to display the object in the active window. Several objects can be displayed simultaneously.

Gray, radio buttons –only ONE object at a time can be displayed. Yellow, square boxes – Filters. Used to filter out different parts of a 3D grid.



Opening and Saving Petrel Projects 1 1. Open Project: Opens an already saved Petrel project (.pet). 2. Save Project As: Saves the Petrel project, prompting you for a new name. The .pet file, the .ptd data folder, and the .sim folder are saved.

1

2 3

3. Automatic Save: Automatically saves the Petrel project, overwriting the current saved version. Should be used with caution.

Petrel File Management

The .pet file contains the index of all data in your project.

Note: When making a backup or sending your project to support, you must include the two associated directories, not just the .pet file – all it contains is the index, none of the data!



Petrel File Management

The .sim directory contains a directory for each case you create, plus the Cache__ directory for temporary index files

Each simulation case directory contains the simulator keyword input files and result files

Exercises – The Petrel user interface The following exercises give you a general introduction to Petrel. Exercise Workflow • Starting Petrel • Petrel interface • Display windows • Object settings • Editing of input data Exercise Data In this exercise, we use the project Dataset > Completed_2010.pet.

Starting Petrel Start the Petrel program by double-clicking on the Petrel icon on the desktop. If a bitlock is used, an introduction window to Petrel will open before the Petrel program window opens up. If you are not using a bitlock (dongle), you will first see a “Net License Modules” dialog asking which module package you want to run. At your location, you may have several levels of licenses. You should use the license that has the functionality you need for the work you are doing. 40 • The Petrel User Interface


Exercise steps 1. Start Petrel. You can find the data used in this course in a folder called Dataset. This folder also contains some completed exercises. These are stored in the 2010 backup projects folder. 2. Open the training project. Do this by clicking File > Open project and select the Completed_2010.pet file from the Dataset directory. 3. Copy the project: Save it to your Student directory by selecting File > Save as. Give it a new name and click Save. Online Help Manual The Online Help Manual is a document that comes with each installation of Petrel. It is the most extensive documentation on Petrel. You open it by clicking Help in the menu bar.

Petrel Interface The Petrel user interface is separated into two main window areas. These are the Petrel explorer panes and the Display window with the Function bar on the right hand side. The available tools in the Function bar depend on which process is active. At the top of the Petrel interface is a standard menu bar and a toolbar. All data that is not connected to a 3D grid is stored on the Input pane. Examples are wells and well top (well picks), rock physics functions, and fluid models. Data that belongs to a 3D grid is stored together with the 3D grid on the Models pane. Examples are, surfaces that are defined as part of the 3D grid (in Petrel called Horizons), grid properties such as porosity, and fluid contacts. The simulation grid properties (the output from simulator, for example, pressure, oil saturation (SOIL)) are stored in the Results pane. Exercise steps 1. Click on the Input pane. Right-click the Wells folder and select Expand (recursive) from the menu. The folder with sub folders is now expanded. Right-click the Wells folder again, and select Collapse (Recursively). 2. Right-click on different folders to see which options are available. Select Settings from the list. A window providing Reservoir Engineering


If any of the panes disappear, go to the View tab in the Menu bar and select Panes to reopen them.

access to functions and settings for the selected folder opens up. The Processes pane contains a list of all available processes in Petrel. They are sorted in the order which they are typically performed. Some of the processes can only be run once the process above in the list is completed. For example, you must create a 3D grid before you can insert horizons, and you must define a fluid model before you can define a simulation case. Processes that are grayed out cannot be used until the process listed above is executed. Like most PC software, the menu bar has the standard File, Edit, View, etc. drop-down menus. In addition, on the right hand side of the Petrel interface there are icons in a toolbar with additional Petrel related functionality. This toolbar is called the Function bar, and the tools available depend on which process has been selected in the Processes pane. All of the icons in the toolbars have a descriptive text associated with them. The text appears if you move the mouse pointer over an icon. Exercise steps 1. Click on each of the items in the menu bar to see the tools available. You may want to experiment with some of the options. 2. Slowly move the mouse pointer over the icons in the toolbar. Text will appear describing the function of each icon.

Display window A variety of windows can be displayed, examples are 3D and 2D windows, well section windows, function windows (for plotting), and interpretation windows (for seismic interpretation). Exercise steps In this exercise, you will use a 3D window. 1. Open a 3D window by selecting New 3D window from the Windows menu in the menu bar. 2. Display an object from the Input pane by selecting the check box next to it. Click on the Viewing mode button (at the top of the function bar) and move your mouse pointer over the display. A hand should appear instead of the pointer. This 42 • The Petrel User Interface


means you can manipulate the display. 3. Left-click and move the mouse to rotate the object in 3D. 4. Hold the SHIFT or CTRL key down, left-click, and move the mouse. This will pan the object. With a three button mouse, you can use the mouse wheel to pan the object. 5. Hold both the SHIFT and CTRL keys down, left-click, and move the mouse. This will zoom the object. With a three button mouse, you can use the left and middle button to zoom. 6. Press the ESC key. The hand now changes back to the regular mouse pointer. You can also use the Select/pick mode button to do this (on the Function bar). 7. Click on an item in the display, using the mouse pointer. Note the information that is displayed in the status bar at the bottom of the window.

Object settings Whether you are importing files, building a new project, or reviewing someone else’s project, the Statistics tab of the object settings provides you with valuable information. Exercise steps 1. In the Models pane, right-click the 3D grid named Fine grid and select Settings. 2. Go to the Statistics tab and check the size of the 3D grid. You can check the minimum and maximum values for X, Y, and Z. You can also find the number of cells and the average increment in all spatial dimensions. 3. Go to the Properties folder of the 3D grid, and check the statistics for a grid property. For instance, check the range of the permeability or porosity. 4. Check the statistics of the Properties folder or of another file folder. The Statistics tab is read-only and is used for information and quality checking (QC). To change the appearance of an object, you need to use the Style and Info tabs. Exercise steps 1. In the Models pane, right-click a property in the Properties folder under the 3D grid Fine. Select Settings and go to the Reservoir Engineering


Info tab. Note that you can change the name of the property by entering a new name and clicking Apply. The name of any object can be changed in its Info tab. 2. From the Info tab, the template can also be changed. Click on the arrow alongside the template name to see the list of available templates to choose from.

3. Open a 3D window, and clear it of all items (Window > Clear all visualizations) and select to view one of the Horizons under the Fine grid. 4. Right-click the Horizons folder, select Settings, and go to the Style tab. Here you can specify display options. 5. Open the Grid lines tab and select the check box Show to view grid lines. Click Apply and observe that you can now view the grid lines on the horizon. 6. Deselect to view the grid lines, and open the Contour lines tab instead. Select the check box Show, then click Apply and observe the changes. You can also specify the thickness and the color of the contour/grid lines in the Style tab. 7. Select to view the faults in the 3D window along with the horizon by select the check box in front of the Faults folder under the 3D grid. 8. Right-click the Faults folder, select Settings and go to the Edges and intersections style tab. In the Lines sub-tab, you can select whether to display pillars on the fault. The pillars define the mesh cell edges in the Z-direction. 44 • The Petrel User Interface


Exercise steps 1. Right-click the Porosity property under the Properties folder of the Fine grid, and select Settings. Open the Histogram tab to view the distribution of values. 2. Similarly, go to the Histogram tab in the Settings of Permeability. View the distribution of the 3D grid property. 3. Insert a New histogram window from the Window menu. Select to display the Porosity property from the Fine grid. You can use function windows to view simulation results. The next exercise will show you how to select the data for display in a function window.


All objects have an Info and a Statistics tab in the Settings dialog. Some objects have more tabs. For 3D grid properties, you will probably find the Histogram tab useful.


Exercise steps 1. Open a New function window. 2. Select vector to view: a. Go to the Cases pane, and select the case Aquifer. b. Go to the Results pane, and select the check boxes in front of Oil production rate under the folder Dynamic results data > Rates. c. Under the Identifier folder in the Results pane, expand the Well folder and select P06. Thus, we will only view results for well P06. d. Further down in the Results pane, you can find the folder Source data type. Expand this folder to select which source data you want to display. Select Observed data. Now, both simulated and observed data will be displayed. You should see oil production rate as a function of time for well P06 in the function window. With the default settings, simulated and observed data are shown as a solid line and circles respectively. e. Go to the Cases pane and select Aquifer_RESTART. This is the simulation case containing the strategy on how to operate the field in the future, and display prediction for well P06. 46 • The Petrel User Interface


3. Change the display options for the function window: a. Your function window is stored in the Windows pane. Expand the folder Function window, and then expand the Function 1 folder. b. Turn the Symbol legend and the Header on and off. c. Right-click Axis, and select Settings. Go to the Ticks tab to specify the increment in x and y in the function window. Go to the Annotation tab to change the size and alignment of x- and y- axes labels. d. Go to the Plot tab. In the Line style tab, you can change the thickness of the lines in the Function window.

Lesson 2 – Making a simple grid with simulation fault



Make simple grid Make a grid without faults

The Make simple grid process, which is located under Utilities, makes it easy to create a grid without faults. The geometry of the grid is defined by the input to the process. A project boundary can be added, or minimum and maximum values from x, y, and z can be used. Surfaces can be inserted to define horizons in the 3D grid



Make simple grid Result

Skeleton

A top, mid, and base skeleton grid is generated. Further subdivision in the vertical direction is needed.

If the process is run without using surfaces to define horizons, the result is a skeleton grid. A “skeleton grid” is a Petrel term for the framework that is made as the first step towards defining a 3D grid. A skeleton grid consists of a top, mid, and bottom mesh defined by pillars. The pillars define the lateral position of the corners in the three meshes, and the z-position is defined as the bottom, mid point, and the top of the pillars. After the skeleton grid is generated, it needs to be further subdivided in the vertical direction. This is done by inserting surfaces. The topmost and the bottommost surface that are inserted define the top and the bottom of the final 3D grid, hence, the top and the bottom skeleton grid are usually outside the final 3D grid. The reason why 3D grids are generated this way in Petrel is that the gridding process starts with modeling the faults, which are defined using pillars. Those pillars are then used to define the geometry of the 3D grid. The processes used to make grids based on fault modeling are Fault modeling and Pillar gridding. Reservoir Engineering


Make simple grid With Insert Horizons

Skeleton with horizons If you have surfaces that describe the horizons, you can enter them as input.

If you have surface data in the Input pane that describes the horizons, you can drop them into the Input data tab of the Make simple grid process. The result will be a skeleton grid with horizons.



Make simple grid Vertical subdivision Make Horizons Insert a horizon in the grid to define different zones. Layering Further subdivision is done by employing the Layering process.

Vertical subdivision The Make horizons, Make zones, and Layering processes are used to perform further vertical subdivision. Make Horizons - This process usually defines the main depositional units of the 3D grid and are, in most cases, the layers identified and interpreted on seismic data. The Make horizons process samples input surfaces into the 3D Grid. Note that a “Horizon” in Petrel is a surface that is a part of the 3D grid. Make zones – This process defines the sub-units of the 3D grid. The process inserts additional horizons (and zones) into the 3D grid by inserting isochores up or down from the previously input horizons. The isochores can be gridded thickness maps or calculated directly from well tops. Zones can also be defined as specific thickness intervals or percentages of the main zone. Layering – The final step is to make the final vertical resolution of the 3D grid. To keep the modeling simple, we will not perform the Make zones process. That is, we assume that the stratigraphic layering is defined by the surfaces that we insert. Then we will do layering to obtain a suitable resolution for simulation. Reservoir Engineering


Make Horizons 1. Append desired number of horizons in the table. 2. Drop in interpretations or surfaces using the blue arrow.

The Make Horizons process Double-click on the Make horizons process to open its process dialog and select the Horizon tab. In the table that appears, insert the number of horizons to be generated. The Multiple drop option allows you to insert a list of items in one go into the Input#1 column: Make sure your input horizons are sorted in the correct stratigraphic order in the Input pane, then select the first item, and click on the first blue arrow under Input#1. All of the input horizons will then be inserted in the same order as they appear in the Input pane. Horizon names are updated according to input names, but can be overwritten if desired. Horizon Type: You should specify whether the horizon is an Erosional, General, Discontinuous or a Base surface. • Erosional surfaces will erode surfaces below • Surfaces above a Base surface will be on lapped to the Base. • Surfaces above a Discontinuous surface will be on lapped on it and surfaces below will be truncated by it. • A general surface will be truncated by any other surface. 52 • The Petrel User Interface


Make horizons Result

The horizons appear in the Models pane. Select the check box to view in a 3D window.

Available for displaying: 1. Edges - to see zone division 2. Zone filter - to view selected layers

Make Horizons – Output Horizons folder – The layers added in the Make horizons and Make zones process will be stored in the Horizons folder. Fault filter – The fault filter will allow you to visualize the fault throw for just one horizon at a time and is mainly used for mapping purposes. Zone filter – A zone in Petrel is defined as the thickness between two horizons, and is created in either Make horizon or in the Make zones process. The zone filter allows you to visualize the edges and the I- and J- intersections of the 3D grid zone by zone. The zone filter is also applicable for properties when we generate these in the 3D grid.



Layering 1. Specify the Zone division. 2. Specify number of layers (Proportional), cell thickness (Follow top/Base) or Fractions.

Proportional Follow Base Follow Top Fractions Follow Base with Reference

The Layering process After the Make horizons (and the Make zones) process is run, further layering is inserted by running the Layering process. You can select four different ways of doing the layering: • Proportional: The zone will be divided into Number of layers, equally thick layers • Follow base: The zone will be divided into layers with thickness Cell thickness, starting to build from the horizon below. • Follow top: The zone will be divided into layers with thickness Cell thickness, starting to build from the horizon above. • Fractions: The zone will be divided into a number of layers with relative thickness as given in the input. Example: If the input is 1, 2, 2, the zone is divided into three layers where the two last layers are twice as thick as the first one.



The illustration above shows three different ways of specifying the layering; Follow base, Fractions and Proportional. Note that the zone division should reflect the horizon type. If, for instance, a horizon is of type Base, the zone above should be of type Follow base, Proportional, or Fractions. Proportional and Fractions give the least “pinched out” layers and are usually best for simulation grids.



Model a fault Digitizing

Employ the Make/edit polygons process to digitize a line that defines the fault plane. The new polygon appears at the bottom of the Input pane.

A simulation fault can be inserted into the simple grid at the position of existing grid nodes. To approximately give the geometry of the new fault, you can draw a polygon within the simple grid. The Make/edit polygons process is placed under Utilities on the Processes pane. When the process is active, tools for digitizing polygons appear in the function bar at the right of the display window. Use the process to digitize a line that defines the geometry of the fault. The new polygon is stored at the bottom of the Input pane.



Model a fault Convert to fault

The polygon can be converted into a fault in the active grid

To insert the fault into the grid, make sure that the grid is selected in the Models pane. Then right-click the polygon you just made, and select Convert to fault. The polygon is then converted into a fault in the active grid. The new fault is stored on the Faults sub-folder of the 3D grid.



Model a fault

Define transmissibility

Use the Fault analysis process to assign transmissibility to the fault

You need to assign a transmissibility multiplier to the fault in order to use it in a simulation. The transmissibility multiplier defines to which degree the fault is a barrier to flow. A multiplier of zero means that no flow goes through the fault. To assign a transmissibility multiplier to a fault, make sure that the fault is active, then open the Fault analysis process. In the dialog that opens, select to assign a constant multiplier, or to define a multiplier based on standard equations. A new property is created and stored under the Fault properties folder in the Models pane. Details of how to define the transmissibility multiplier will be provided later in the course.



Exercises - Making a simple grid a with simulation fault In this exercise, you will make a simple simulation model of a twophase black oil case. You will start by defining a simple grid with a vertical fault. You will then go through all of the steps required until you have a model ready for running a simulation. And finally, you will run the simulation and view the results. Exercise Workflow • Make a simple grid • Insert a simulation fault Exercise Data In this exercise, we use the Start_2010.pet.

Making a simple grid Exercise steps 1. Open the Start_2010.pet project. 2. Open the Make simple grid process located under Utilities in the Processes pane. 3. Select a name for the new grid, for example Simple. 4. On the Input data tab, select the Insert surface option. 5. Drop in the surfaces Top reservoir, Mid, and Base from the Surfaces folder on the Input pane by clicking the Append item in the table button .



6. Drop in the Project boundary from the Input pane into the Boundary field by clicking the blue arrow. 7. Select the Geometry tab, and click the Get limits from selected button. As the project boundary is selected on the Input pane, Petrel will use that as a boundary for the grid.

8. Select a Grid increment of 350 m in both the X and Y direction. Click OK. 60 • The Petrel User Interface


9. Your new grid is stored in the Models pane. Select to view the skeleton grid in a 3D window. 10. We will now define the vertical sub-division of the 3D grid. Open the Layering process under Corner point gridding. Divide ‘Zone 1’ into 7 layers and ‘Zone 2’ into 3 layers. Press OK. Select to view ‘Edges’ under the 3D grid in the Models pane to see the result of the layering.

Making a simulation fault In this exercise, you will add a “Simulation fault” to the model. If you want to add a fault with throw, you need to use a more advanced gridding processes in Petrel. That is, you will have to use the Fault modeling and the Pillar gridding process. Exercise steps 1. Open a 3D window and select to view both the Top reservoir horizon and the faults from the Fine grid. 2. Observe that the faults have a throw. For example, across Fault5 the throw is so large that there is no communication across. We will now insert a simulation fault in the simple grid to model this behavior. 3. Open a new 2D window and display the Base horizon from the Simple grid and the Project boundary from the Input pane along with Fault5 from the Fine grid. 4. If you cannot see the fault, open the Settings of the Faults folder of the Fine grid, and make sure the option Show horizon-fault lines is selected. Reservoir Engineering


5. Digitize a line that will be used to define the fault plane by first selecting the Make/edit polygons process in the Utilities folder in the Processes pane. Then: a. Activate the Make/edit polygons tool in the function bar. Select the Add new points tool . b. Digitize a line that follows Fault5 by pointing in the display and left-clicking. Add a point in the grid cell closest to the project boundary to make sure the fault is extended all the way to the boundary.

6. The polygon is stored at the bottom of the Input pane. Rename it to “Fault polygon” by opening the Settings for it and changing the name in the Info tab. 62 • The Petrel User Interface


7. Make sure the Simple grid is selected on the Models pane. 8. Right-click on the polygon you just made, and select Create simulation (grid) fault from the drop-down menu. The new fault is stored in the Faults folder under the simple grid on the Models pane.

Exercise steps 1. Open a 3D window and select to view your new fault. 2. Open the Fault analysis process that is located in the Property modeling folder. 3. Enter a constant transmissibility multiplier of 0 (sealing fault) Click OK. 4. Save the project.



Summary The basics of the Petrel user interface were presented in this module. In particular, how to open and use windows and how to access and alter the settings of objects. Also introduced were the eight different panes in Petrel which store and provide access to data, processes, windows, workflows and simulation results. In addition, how to make a simple simulation grid with layering based on surface information was presented along with how to add a fault to such a grid and how to assign properties to the fault.



Module 3 - Functions Introduction In this module, how to make fluid models (PVT), saturation functions (relative permeability and capillary pressure), and rock compaction functions in Petrel, will be covered. Prerequisites No prerequisites are required for this module. Learning Objectives In this module you will learn: • How to create a correlation based black oil fluid model • How to define the initial contact depths and pressure • How to create correlation based saturation functions • How to create rock compaction functions based on correlations • How to import fluid models and rock physics functions from keyword files • How to edit and visualize the functions in Petrel


Functions • 65

Lesson 1 - Make fluid model

Make fluid model

The Make fluid model process allows you to create black oil models from correlations and to create compositional and thermal models. In this course, we will only use black oil models, but we will briefly explained how to create compositional models. Correlation library The correlation library we use incorporates many published correlations, some of which use the separator conditions as input. All of the correlations have been tested against an extensive database of actual PVT (pressure-volume-temperature) experiments at the Schlumberger Reservoir Fluids Center in Edmonton, Canada. Petrel selects which correlation to use based on the input data you provide – the API gravity, the reservoir pressure, etc. The library contains about 70 black-oil correlations - including the ones most commonly used in the industry. 66 • Functions


Black Oil and Compositional Models ECLIPSE Blackoil and FrontSim • Black oil simulators • One component of gas and one of oil in both vapor and liquid phase

ECLIPSE Compositional • Compositional simulator • Both the vapor and the liquid phase consists of several components

Rv

Rs

There will always be two, or frequently three, phases present in the reservoir during its producing life (oil, gas, water). The proportions, the composition and the physical properties of the phases may change as production proceeds, and pressures change. All of the phases are considered compressible, although to different degrees. In a black oil model, the temperature is assumed to be constant. Typical temperatures at reservoir conditions are 350K~77C~171F. Also, since both the liquid hydrocarbon phase and the vapor phase are assumed to consist of mainly one component, it is customary to name them the oil and gas phase, respectively. The compositional behavior is modeled by allowing some of the gas component to be dissolved in oil and some of the oil component to be vaporized in gas. A compositional fluid model represents the hydrocarbon fluid by a set of components (typically 6-12 for reservoir simulation). An equation of state is then used to determine the physical properties of mixtures of these components as a function of pressure and temperature and the properties of the individual components.


Functions • 67

Appropriate Black Oil Models Fits the Black Oil model.

Pressure

Unsuited for black oil simulation (use Compositional simulation).

G: Near Critical Fluid

F: Wet Gas, Retrograde

A: Dead Oil C: Live Oil, Saturated

Approximated by Black Oil varying gas/oil and oil/gas ratios to mimic small compositional changes. B: Live Oil, Initially Undersaturated

D: Dry Gas

E: Wet Gas

Temperature

Phase diagrams The hydrocarbon behavior in a reservoir is often described in terms of a phase diagram as showed in the illustration above. The phase diagram relates the fluid state to pressure and temperature in the reservoir. The upper line of the phase envelope represents the lowest pressure and temperature limit for the existence of a liquid phase. This line is called the bubble point line. The lower line represents the upper limit for pressure and temperature for the existence of a vapor phase. This line is called the dew point line. The area between the two lines is pressure and temperature conditions where both a liquid and a vapor phase is present simultaneously. The point where the bubble point line and the dew point line meet, is called the critical point. At this pressure and temperature condition, the vapor and the liquid properties are equal. Pressure-temperature conditions close to the critical point cannot be modelled using a black-oil model.

68 • Functions


Make a Fluid Model 1. Select Create new to define a new fluid model.

1 2

2. Specify Model type.

Note : All fluid models will be stored in the Input pane.

In the process dialog, you need to specify whether to make a black oil, compositional or thermal fluid model.


Functions • 69

Compositional Model 1. Select equation of state from the General tab.

1

Note: There is no support for tuning an equation of state to match laboratory measurements.

2. Append a row for each component.

You can select pre-defined components from the drop-down menu. 2

3. Go to the Interactions tab to give interactions and to the Samples tab to give samples. 3

When you make a compositional model, you must first select an equation of state at the General tab. Note that there is no support for tuning the equation of state to laboratory measurements. For that, you will have to use PVTi and import the resulting matched equation of state. When you add a new component on the Components tab, you need to type in the molecular weight and then click the Fill table button to fill in the rest of the table according to the equation of state. Note that if you later change the equation of state, you must return to the Components tab and click the Fill table button again.

70 • Functions


Make a default Compositional Model 1. Select model type – Compositional. 2

1

2. Use the drop-down menu to specify default model. All sub-tabs are filled with preset values.

Make a default Black Oil Model

1 3 2

1. Select Black oil as Model type. 2. On the General tab, specify which phases are required (enter required properties in the following tabs). 3. Or use one of the defaults. 4. Specify an initial condition.


4

Functions • 71

There are four default black oil models to select from: Dead oil. Two phases, oil and water. Bubble point pressure lower than minimum reservoir pressure, hence no gas will boil out of the oil. Heavy oil+gas. Three fluid phases, oil, gas, and water. The oil has API gravity of 26. Light oil+gas. Three phases, oil, gas, and water. A lighter oil with API gravity of 45. Dry gas. Two fluid phases, gas and water. To make a default model, select one of the models from the drop-down list and go to the Initial conditions tab to specify the initial fluid contacts.

Make a model using the settings General tab • Select phases. • Enter pressure and temperature in the reservoir.

In addition to the four default fluid models, you can make black oil models by filling in the settings in the process dialog. Based on the settings, Petrel will select a model based on correlations. The General tab In the General tab, you specify which fluid phases that are present and also the reservoir pressure and temperature. Reservoir conditions. This is where the minimum and the maximum pressure in the reservoir is specified. In addition, you must enter the temperature in the reservoir. Separator conditions. Here you can specify the pressure and the temperature at separator conditions. Some of the correlations need information on separator conditions. 72 • Functions


The Gas tab Gas Information on the gas phase composition entered here is used to select correlations.

Correlations Leave as Default to allow Petrel to select correlations based on your input.

Gas properties. Enter the density or the gravity of the gas phase. If you are defining a dry gas, you must type in the vaporized gas/oil ratio. You can also select which correlations to use or you can make Petrel select, based on the input you give. If you have information on the concentration of each component of the gas phase, this can be entered here. Note that this option is only used to select which correlations to use, it does not mean that you are defining a compositional model.


Functions • 73

The Oil tab Specify gravity and bubble point pressure. Correlations are reported on the Statistics tab of the fluid model

Oil properties. Here, you need to specify the oil density or the oil gravity (API gravity: The usual range starts with water density at 10 degrees and rises to volatile oils and straw colored condensate liquids around 60-70 degrees). In addition, you must enter the Bubble point pressure or the Solution gas/oil ratio at the oil/gas contact. Note that if the bubble point pressure you supply is lower than the minimum reservoir pressure, then no gas will boil out of the oil. Consequently, you get dead oil. Also, notice that unless you plan to give a depth dependent Solution gas/oil ratio, the bubble point pressure must be equal to the pressure at the gas/oil contact as specified in the Initial conditions tab. You can either select correlations, or leave it to Petrel to select based on the input you give. Notice that the correlations that are used to make the fluid model are listed on the Statistics tab of the settings dialog for the fluid model.

74 • Functions


Initial conditions tab

1 1. From contact set.

2

3

2. Define in the table. 3. Add columns to the table to add initial condition regions.

Initial conditions tab In the Initial conditions tab, you can give the initial fluid contacts as well as the pressure and the capillary pressure at those contacts. This information is used in the simulator to calculate the initial pressure and phase saturations in every grid block. For each fluid region, you must specify a reference depth (datum) and a corresponding pressure, gas-oil contact depth, and water contact depth (depending on which phases you have). In the Define simulation case process you will have the opportunity to associate each of these initial condition regions with a region of the grid. There are two ways you can define your initial conditions: Contact set: If you have an existing contact set, you can select the Use contact set option and drop in the contact set from the Petrel explorer. The option Target number of initial conditions will control how many regions to make from a contact set (for example, if a tilted surface is made in the Reservoir Engineering

Functions • 75

To keep the fluids in a stair step condition, you will need to define the model as such (with an active aquifer, capillary pressure, etc). If you just put a tilted surface for the contact, and then run the simulator, the fluid will gradually slump down to a flat contact.

Make contacts process). This algorithm is iterative and cannot guarantee to get exactly the number of targets specified. For example, if you enter 10, but there are only two distinct values in the surface, you will only get two regions. Table: If you not using contact set, you can enter the details of each initial condition in a table. The table consists of a column for each initial condition region; columns can be added or removed using the usual Petrel table manipulation buttons. By default, the gas-oil contact is set as Datum. Also, the pressure at Datum is defaulted using a pressure gradient of 0.0981 bar/m over the depth given by (surface elevation - datum depth). To enter a specific pressure or datum depth, select the check box. Note that unless you plan to give a depth table for solution gas/oil ratio and bubble point pressure, the pressure at the gas-oil contact must be equal to the bubble point pressure input, specified on the General tab.

Make contacts Make contacts is the process where the contacts to be used in the Volume calculation and Simulation processes are made

76 • Functions


To use contacts as input to the Make fluid model processes, you must define them in a separate process in Petrel, called Make contacts. The purpose of this is to be able to enter different types of contacts, such as constant values, dipping contacts and surfaces, and you can choose to use different contacts for each zone and each segment or the same contacts for the entire 3D model. Another purpose of contacts is to visualize them together with one of the horizons. This will show the contact contour on the surface together with colored intervals for each hydrocarbon interval. This is useful when displaying the aerial extent of the hydrocarbon intervals.

Make contacts

Define fluid contacts

1. Append the number of contacts.

1

2

2. Define the contact type and name. 3. Define the contact level.

3

Can be a different value/surface for each segment and zone.

Make contacts - Procedure 1. Open the Make contact process. 2. Choose to Create new contact set. 3. Enter the type of contacts to be created, and change the name (if other than default). 4. Enter the contact level.


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Contact level • Can be a constant value or a surface. To enter a constant value, type the value directly into the cell. If it is a surface, select the little check box and use the blue arrow to copy the surface that represents the contact into the cell. • To use different contacts for each segment and zone, clear the options Same for all zones and Same for all segments.

Fluid variations with depth Vertical variations in PVT must be given in a spreadsheet. Right-click an Initial condition and select Spreadsheet to enter a depth table.

Specify the bubble point or the Rs value at each depth. If you specify one, then the other is calculated using the correlations.

Composition of oil is frequently a function of depth • Solution gas/oil ratio (Rs) or Bubble point pressure (Pb • Vaporized oil/gas ratio (Rv) or dew point (Pd) (No correlations available to create vaporized oil PVT – input manually or import) To model the variation with depth, you have to fill in the Spreadsheet located under the Initial condition sub-folder of the fluid model folder. You can specify the bubble point or the Rs value at each depth. If you specify Pb, then Rs will automatically be calculated and vice-versa, using the correlations the fluid model is based on. 78 • Functions


Entering a depth table is optional. If a table is not entered, the dissolved gas concentration in under-saturated oil is set equal to the saturated Rs value at the gas-oil contact everywhere. This is the Rs value that you specified on the General tab when you made the fluid model. If the bubble point pressure (specified on the General tab of the Make fluid model process) is not equal to the pressure at the gas-oil contact (as specified on the Initial conditions tab), a depth table is required. At any position in the reservoir, the Rs value derived from an Rs or Pb versus depth table, is subject to an upper limit equal to the saturated value at the local pressure, since the Rs value cannot exceed this.

Spreadsheets You can view/edit a fluid model in spreadsheet format. You can copy and paste to/from existing tables.

By right-clicking the oil or gas phase of the fluid model, you can access the data in a spreadsheet format. Data can be copied/pasted from/to those spreadsheets from Excel.


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Plotting Fluids data can be plotted in a function window.

Import Black oil models exported from PVTi can be imported. The status of the import is reported in the message log.

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You can import fluid models generated in PVTi, or you can import Eclipse keyword files.

Exercises – Make fluid model There are several ways to create a fluid model in Petrel. You can use the Make fluid model process to generate a fluid model from correlations, you can import data or you can define a fluid model by using spreadsheets. Exercise Workflow • Make a black oil fluid model • Reviewing fluid model settings • Import a keyword fluid model • Plot the fluid model Exercise Data In this exercise, we will continue to use the project from the previous exercise.

Make a black oil model from correlations In this exercise, we will create a black oil fluid model based on correlations using the Make fluid model process in Petrel. The output from the process is a fluid model that can be used by the simulator. Exercise steps 1. From the Processes pane, open the Simulation folder and open the Make fluid model process. 2. Select Create new fluid model. 3. Click on the Use presets button and select Light oil + gas from the drop-down menu. Observe that the process window is filled with default values. 4. On the General tab, change the Maximum pressure to 460 bar.


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5. Inspect the Gas tab, accept the default settings. 6. Select the Oil tab. Change the Bubble point pressure to 200 bar. 7. Go to the Initial conditions tab. To specify the initial reservoir conditions for the model, you can either drop in a contact set or you can enter a table of contact depths and pressures. In this exercise, we will use the table and enter a value for the gas-oil contact to -1600m and the water contact to -2600 m. 8. Enter a pressure at datum (the gas-oil contact) of 200 bar.

If the datum depth lies above the gas-oil contact, the pressure refers to the gas phase. If the datum depth lies below the water-oil contact, the pressure refers to the water phase. Otherwise, the pressure refers to the oil phase.

9. Click OK in the Make fluid model process dialog. 82 • Functions


Reviewing fluid model settings In this exercise, we will inspect the settings for the fluid model we just created to see how we can edit and change the model. Exercise steps 1. In the Input pane you can now see that a Fluids folder has been added. This is where the fluid models are stored. 2. Expand your fluid model inside the Fluids folder and then right-click on Oil and select Spreadsheet from the context menu. This opens a spreadsheet view of the oil properties that vary with pressure.

Import a keyword fluid model In this exercise, we will import a fluid model from a keyword file. This file can be an included file to the simulation deck, or the main .DATA file of the simulation deck. Exercise steps 1. Right-click on the Fluids folder and select Import (on selection). Navigate to the ImportData > Functions > FLUID.INC file, and click Open to do the import. 2. On import, you may get a message that some keywords were not imported. You can find those keywords in the Message log. These keywords do not contain PVT data. 3. After importing, a new fluid model is added to the Fluids folder in the Input pane. Check the imported data by using the Settings panel and the spreadsheets. 4. The fluid you imported does not have an initial condition, hence, an initial condition must be added before the fluid can be used in a simulation model.

Plotting the fluid model In this exercise, we will plot the fluid model in a function window. Exercise steps 1. Insert a New function window from the Window menu, and select the check box next to Oil formation volume factor in the Oil folder of the imported Black oil model 1. 2. Use the Select/pick mode tool Reservoir Engineering

and click anywhere on Functions • 83

any of the curves. The property name and value appear in the status bar. If you cannot see the status bar, enable it with the View > Status bar command. 3. Deselect to view the Oil formation volume factor and select the check box next to Oil viscosity instead. 4. Any changes made in any of the settings panels and spreadsheets will be reflected in what you see in the function window.

84 • Functions


Create multiple viewports – Optional In this exercise, we will set up a new plot window with four function viewports so we can make a report of the fluid model and inspect more data in one view. Exercise steps 1. Insert a New plot window from the Window menu. 2. There are two ways to create multiple viewports in the plot window: a. Go to the Windows pane and find the inserted plot window. Open the settings for Plot window 1 [Any] and go to the Setup multiple viewports tab. Or, b. From the toolbar, click on the New object in window button on the toolbar and select Create/align multiple viewports.


Functions • 85

3. In the settings for ‘Plot window 1 [Any]’ dialog, select Function viewport(s) from the New viewport type dropdown menu. Define Number of rows: 2 and Number of columns: 2. Then click the Setup viewports button and close the settings window by clicking OK. 4. You should now have four function viewports ready to use for plotting the line data. The active viewport is shown with a red border. Click inside a function viewport to make it active. 5. As an example, select the following data to plot from the Light oil + gas fluid model: a. Top left viewport: Oil formation volume factor. b. Top right viewport: Oil viscosity. c. Bottom left viewport: Pressure and the fluid contacts from Initial condition 1. d. Bottom right viewport: Gas formation volume factor. 6. You should have a plot window similar to the one shown below: 86 • Functions



Functions • 87

Lesson 2

Make rock physics functions

Make rock physics functions

Capillary pressure curves

Relative permeability

Rock compaction

The Make rock physics functions process is used to create functions that represent the physics of the rock and the interaction between rock and fluids, or saturation functions and rock compaction functions.

88 • Functions


Rock compaction function Rock compaction function Used to make rock compaction tables from a choice of correlations to model compaction drive.

Rock compaction functions are tables showing pore volume multipliers versus pressure, or a single rock compressibility value used by the simulator to calculate the pore volume change. The compaction can be thought of as the reduction in the pore volume as a function of pressure. Creating rock compaction functions using the Make rock physics functions process will also create a transmissibility multiplier versus pressure curves. These are set to 1.0, by default.


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Rock compaction function Use presets There are three preset compaction functions to select from.

Or specify 1. Correlation 2. Rock type 3. Number of table entries Then give: 1. Porosity, constant or property 2. Pressures

By clicking the Use presets button, you will be given three compaction functions to select from. Alternatively, you can manually fill in the fields. If you select the correlation User defined, you need to supply a compressibility and a reference pressure (equivalent to using the ROCK keyword). Otherwise, the compressibility is computed using the correlation you select from the drop-down menu (the ROCKTAB keyword is used). In both cases, the result of the process is a curve showing pore volume multipliers as a function of reservoir pressure. The multiplier is always one for the reference pressure, meaning that at this pressure the pore volume is equal to the initial pore volume. Note that when adding a rock compaction function to your simulation case, the simulator will no longer compute the (initial) pore volume taking only the porosity property that you supply on the Grid tab of the Define simulation case process as input. Now the simulator is also using the rock compaction curve. That is, for each grid block a pore volume is assigned by multiplying, the original grid pore volume with the pore volume multiplier. Consequently, if the pressure for a grid block is equal to the reference pressure, the volume is unaltered. If the 90 • Functions


pressure is lower, the volume is reduced. However, if you want to model a reservoir that is already compacted at the beginning of the simulation, you need to define a reference pressure that is accordingly higher than the initial cell pressures. If you want to use the pore volumes as given by the porosity property to initialize your model, you have to use the Keyword Editor and change the second entry of the ROCKOPTS keyword to STORE.

Saturation function

Saturation function

Make relative permeability curves based on Corey correlations

Used to calculate initial saturation in each cell Used to calculate the phase mobility

When two or more immiscible fluids (for example, oil and water) are present in the formation, their flows interfere. Therefore, the effective permeability to oil flow (ko) or water flow (kw) is reduced. Furthermore, the summation of effective permeability is always less than or equal to the absolute permeability (k). The effective permeability depends not only on the rock itself but also on the relative amounts and properties of the different fluids in the pores. In a given rock, ko and kw will vary as oil and water saturations, So and Sw, vary. Reservoir Engineering

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Relative permeability is the ratio of the effective permeability to the absolute (single homogeneous fluid) permeability, thus, for an oil-water system the relative permeability to water, krw, is equal to kw/k. Similarly, the relative permeability for oil, kro, is equal to ko/k. Relative permeability is usually expressed in percent or fractions and never exceed the unity (1 or 100%). In Petrel, you can use the Make rock physics process to make relative permeability curves as functions of saturation based on Corey correlations.

Saturation function

1. Preset values are available for sand, shaly sand and fracture (for dual permeability models). 2. The number of table entries controls the size of the tables passed to the simulator.

The input to the Corey correlations depends on the fluid phases you select to include in the model. For gas: - Sgcr: the critical gas saturation. - Corey Gas: Corey gas exponent for values between the minimum water saturation and (1 – Sorg). - Krg@Swmin: Relative permeability value of gas at the minimum water saturation. - Krg@Sorg: Relative permeability value of gas at the residual oil saturation. 92 • Functions


For oil: - Sorw: Residual oil saturation to water. Note that (1 – Sorw) > Swcr - Sorg: Residual oil saturation to gas. Note that (1 – Sorg) > Swcr - Corey O/W: Corey oil exponent for values between the minimum water saturation and (1 – Sorw). - Corey O/G: Corey oil exponent for values between minimum water saturation and (1 – Sorg). - Kro@Somax: Relative permeability of oil at the maximum value of oil saturation. For water: - Swmin: Minimum water saturation. - Swcr: Critical water saturation. This must be greater than or equal the minimum water saturation. - Corey Water: Corey water exponent for values between Swcr and (1 – Sorw). - Krw@Sorw: Relative permeability of water at the residual oil saturation value. - Krw@S=1: Relative permeability of water at a saturation value of unity. Oil-water capillary pressure: Notice that in the lower part of the process dialog you can enter input to generate a curve for oil-water capillary pressure. You need to provide: - maximum capillary pressure - water saturation when the capillary pressure is zero.


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The figure shows relative permeability curves for a water-wet formation containing only oil and water. The values of krw and kro vary with the saturation. The curves illustrate that at high oil saturation, kro is large and krw is small; the oil flows easily and little water flows. At high water saturations, kro is small and krw is large; now the water flows easily and little oil flows. Irreducible saturations When the Kro value reaches zero, the oil remaining in the pore space is immovable; the corresponding value of oil saturation at which this occurs is the residual oil saturation (Sorw). The Krw curve becomes zero at an Sw value indicated on the figures as Swcr. At this saturation, only oil flows in the formation and the residual water is immobile. In a water-wet formation, there is always a certain amount of water held in the pores by capillary forces. This water cannot be displaced by oil at pressures encountered in formations, so the water saturation does not reach zero. 94 • Functions


Spreadsheets You can view/edit rock physics functions in a spreadsheet. Right-click on the Rock physics functions folder and select Spreadsheet…

Spreadsheets for rock physics functions The spreadsheet for rock physics functions has some basic validation triggers. In the case of saturation functions, the saturation values must increase down the column, and the relative permeabilities must be level and increase or decrease down the columns. In the case of rock compaction functions, the pressure must increase down the column, and the pore volume and transmissibility multipliers must be level and increase or decrease down the columns. The simulator will also run a validation on the data ranges in the tables, and will issue a warning if the end point in the tables exceeds 100% (1.0)

Capillary pressure In a thick reservoir that contains both water and hydrocarbon columns, the saturation may vary from 100% water at the bottom of the zone, to a maximum oil saturation (and irreducible water saturation) at the top. There is a gradual transition between these two extremes in saturation. The transition interval may be very short for porous and permeable formations, or it may be quite long in formations of low permeability. Reservoir Engineering

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Capillary pressure is a function of the elevation above the free water level (FWL) and the difference between densities of the wetting (water) and non wetting (oil) phases.

Capillary pressure data Oil-water

You can make oil-water capillary pressure curves using correlations.

Capillary pressure data Gas-oil

Petrel does not have a correlation for gas-oil capillary pressure data. The data can be entered in the spreadsheet. 96 • Functions


Plotting

Import from keywords

Import rock physics functions

Functions can be imported to the Rock physics function folder. The status of the import is reported in the message log.


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You can insert sub-folders to the Rock physics functions folder to organize the fluid models. This way you can use Petrel as a repository for the rock physics functions you regularly use.

Rock physics functions can also be inserted manually into Petrel by right-clicking on the Rock physics functions folder in the Input pane and selecting the option Insert rock compaction function or Insert saturation function. An empty function will appear in the folder. In turn, this can be right-clicked and you can select the option to open a spreadsheet for editing the function. The function tables can then be entered manually, or copied from an external application.

Exercises – Make rock physics functions There are several ways of creating rock physics functions in Petrel. You can use the Make rock physics functions process to generate functions from correlations, you can import data, or you can define the functions using spreadsheets. Exercise Workflow • Make a saturation function • Make a rock compaction function • Reviewing rock physics functions data • Import a keyword rock physics function • Plotting the rock physics functions Exercise Data In this exercise, continue to use the project you used in the previous exercise.

Make a saturation function In this exercise, we will create saturation functions based on Corey correlations using the Make rock physics functions process. The output from the process will be tables that can be exported for use by the simulator. Exercise steps 1. From the Processes pane, expand the Simulation folder and open the Make rock physics functions process. 2. Select Saturation function from the Function type dropdown menu. 3. Select Create new function, then select Sand from the Use presets drop-down menu. 4. Click Apply in the Make rock physics functions process dialog. 98 • Functions


5. Expand the new Rock physics functions folder on the Input pane. This is where your saturation function is stored. 6. Open a Function window, and select to display the saturation function.

Exercise steps The shape of the relative permeability curve and the number of points in the table is set in the process dialog. 1. Open the Make rock physics functions process again. 2. Select Edit existing function, and then make sure the Sand function is selected from the drop-down list. 3. Change the number of Table entries to 8. 4. Change the Corey O/W to 1 and the Corey water to 2. 5. Change Sorw to 0.15. 6. Click OK. 7. Display the new function in the Function window. Reservoir Engineering

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Make a rock compaction function In this exercise, we will create rock compaction functions based on correlations using the Make rock physics functions process. The output from this process will be rock compressibility tables that can be used by the simulator. Exercise steps 1. Open the Make rock physics functions dialog. 2. Select to create a new function. 3. Select Rock Compaction Function from the Function type drop-down menu. 100 • Functions


4. All the necessary fields on the dialog can be filled in with default values by selecting an option from the Use presets list. Click on Use presets and select Consolidated sandstone from the drop-down menu. 5. Click OK in the Make rock physics functions process dialog.

6. The rock compaction function is stored in the Rock physics functions folder in the Input pane. You can also make a rock compaction function based on constant compressibility. Exercise steps 1. Open the Make rock physics functions dialog. 2. Select Rock Compaction Function from the Function type drop-down menu. Reservoir Engineering

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3. Select Create new function and give the new function the name Constant. 4. Select to use 8 table entries. 5. From the Correlation drop-down menu, select User defined.

6. Enter a Compressibility of 0.00001. 7. Click OK. 8. Display both compaction functions in a function window.

Reviewing rock physics functions data In this exercise, we will inspect the settings for the rock physics functions we just created to see how we can edit and change the functions. We will also plot the functions in a function window and do some graphical editing directly on the curves. Exercise steps 1. Right-click on the Rock physics functions folder and select Spreadsheet from the drop-down menu. This will give you a spreadsheet view of the rock functions. 2. You can select which function to view by using the drop-down menu at the top of the panel. Similarly, you can change between the relative permeability tables and the capillary pressure table by using the drop-down menus. 3. Click Cancel to close the spreadsheet.

102 • Functions


4. Insert a function window from the Window menu and click in the check box in front of one of the saturation functions to plot the curve for that function. 5. There are two ways to edit the functions. You can either make edits in the spreadsheet, or directly on the curves in the function window using graphical tools. There is no undo, so make a copy of a function before you start editing. 6. Click on the Select/pick mode tool in the function bar and click on a point on one of the curves. Information on this point is displayed in the status bar.

7. Click on the Select and edit/add points tool in the function bar. Click on one of the points and drag this to another position to update the function. Note that there is no undo for this operation! 8. Move the mouse pointer a little bit beyond a point on the curve and click on the line itself. Hold the left mouse button and drag. A new point is added to the function. You can move the point, and the function table are updated accordingly. 9. Finally, click on the Selected and edit line tool . Click on one of the points and you will now be allowed to move this up or down, but not horizontally.


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Import a keyword rock physics function In this exercise, we will import rock physics functions from keyword files. The file can be an include file to the simulation deck, or the keywords can be in the main .DATA file of the simulation deck. Note that the path to include files must be reachable. Exercise steps 1. We will import both types of rock physics functions in one operation. Right-click on the Rock physics functions folder in the Input pane and select Import (on selection). 2. Navigate to and select ImportData > Functions > ROCKPHYSICS.INC and click Open to start the import. If there are any keywords that are not imported, they will be listed in the Petrel message log. 3. View the imported data by using both the spreadsheets and the function window.

104 • Functions


Summary How to create a fluid model and rock physics functions using the Make fluid model and Make rock physics functions in Petrel was covered in this module. How to edit the functions in a spreadsheet and to plot the functions in function window was also covered. Finally, you have learned how to import functions from keyword files and how the functions are stored and organized in Petrel.


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Module 4 - Initialize the Model and View 3D Properties Introduction In this module, you will learn how to use the Define simulation case process to initialize the model. We will also explore the 3D viewing options in Petrel. Prerequisites No prerequisites are required for this module. Learning Objectives In this module you will learn: • How to initialize the model • To use 3D visualization windows • How to define and use filters


Initializing the model • 107

Lesson 1 – Initialization of the model

Introduction The Define simulation case process allows the engineer to pull together the 3D grid with the fluid and rock physics functions to initialize the model, that is, to compute initial saturations, pressure and transmissibilities. The process is also used to select which simulator to run, and which development strategy to use.

108 • Initializing the model


Define simulation case Grid properties

Porosity and Permeability is set on the Grid tab of the Define simulation case process.

Porosity and Permeability is automatically inserted on the Grid tab when you select a 3D grid.

Additional Grid Properties • Add a row by clicking • Select template • Drop in the 3D property For example, insert a water saturation to apply end point scaling.



In addition to permeability and porosity (required input), you can drop in other properties that are defined in the 3D grid. For example, you can select to use a local grid set, fault transmissibility multiplier, or endpoint scaling for saturation functions.

Three ways of Initializing Equilibration The simulator computes initial saturation and pressure using the Fluid model and the Saturation function that is inserted on the Functions tab.

Enumeration (Black oil) The user inserts initial saturation and pressure as 3D grid properties on the Grid tab. Restart Initial saturation and pressure is read from a restart file.

Initial gas, oil, and water pressure distribution and initial saturation distributions must be defined in the reservoir model. Pressure data is usually given with reference to a datum depth. In Petrel, the datum depth is mean sea level by default. There are three initialization options: Equilibration – Initial phase pressures and saturation are computed by the simulator, using the fluid model. The equilibration facility is a means of calculating the initial conditions on the basis of hydrostatic equilibrium. If necessary, the reservoir can be divided into separate “equilibration regions” in which hydrostatic equilibrium exists independently of the other regions. The number of equilibration regions is specified in the Make fluid model process. Within each 110 • Initializing the model


equilibration region, all grid blocks must use the same pressure table for their PVT properties, but they can use different rock physics functions tables as specified in the Make rock physics functions process. Enumeration – The initial value of pressure, saturation, and bubble point pressure is set explicitly in each grid block by the user. The 3D grid property must be dropped into the Grid tab of the Define simulation case process. Restart – The initial conditions are read from a restart file of a previous run.

Functions

Black oil (PVT) Left-click the Black oil fluid model (PVT). Drop in the initial condition of the fluid model. Deselect Initialize by equilibration if you use enumeration.



Functions

Black oil regions

Different fluid models can be assigned to different regions. Any discrete property (such as segments) can be used as a region index property.

Fluid model: Spatial variations Initially, the fluid model in reservoirs may vary vertically and aerially. This can be modeled by assigning separate fluid models to separate regions of the model. It is important to understand how the fluid model is used in a simulator with fluid movement. When fluid moves from one region to another, the simulator will change the fluid model used, such as the viscosity and formation volume factor, as the fluids cross into the separate regions. Unless mixing between different oils has occurred or the pressure has changed, the fluid properties will remain the same as they move through the 3D grid.



Functions

Rock physics Drop in: • Relative permeability curves • Rock compaction function Select Region index property to assign different functions to different rock types.

Initialize by equilibration Given the fluid densities, the equilibration procedure sets up saturation against depth curves so that in the transition zone, when two phases are mobile, the hydrostatic pressure variation is balanced by the capillary pressure between the phases.


Separate rock physics functions should be used for each significant rock type.


Equilibration

Compute phase pressures The contacts in the Fluid model are used. Phase pressure is computed using the fluid density as input.

Within each equilibration region, the calculation is performed in two stages. In the first stage, an internal table of phase pressures and Rs and Rv against depth is set up. In the second stage, the fluid conditions in each grid block in the region is computed using interpolated values from the table.



Equilibration

Saturation in the water, oil, and gas zone Oil zone: So = 1-Swmin Gas zone: Sg = 1-Swmin

In the second stage of the equilibration calculation, the local fluid conditions are determined in each grid block in the equilibration region. The internal table is interpolated to obtain the values of Po, Pw, Pg, Rs and Rv at the grid block center depth. The water saturation is determined by inverse look-up of the water capillary pressure table.



Equilibration

Saturation in the transition zones

• Calculate Pcog and Pcow in the transition zone. • Find Sg and Sw by inverse lookup from the capillary pressure curves.

Strategies The Strategies tab can be left blank when initializing the model. Development strategies and Well segmentation will be described later in the course.

You can use a global permeability log to compute the KH term of the connection transmissibility factor. For every well, Petrel will check if it has a permeability log that will be used for computing KH. Otherwise, the grid properties will be used as usual.’ 116 • Initializing the model


Results

3D initial properties Request to write out initial saturation and pressure. Non standard 3D properties can be added using Additional Properties (e.g., bubble point for each cell).

Advanced

Select grid type The Editor gives access to all simulator keywords including those not supported from Petrel.

Select: • Grid export type (OPF default) • Simulator version • Which queue to send the job to



A choice of formats for exporting grid data from the Models pane has always been available in Petrel. However, you can also select these formats from the Advanced tab in the Define simulation case process. The considerations in choosing which format to use are: Pillar geometry: Petrel supports vertical, straight, listric and curved pillar geometry. Several of the export formats only support vertical and straight pillars. If your grid contains curved or listric pillars and you use a format that does not support it, the grid will be distorted on export. Check this in the Statistics tab of the grid settings. ASCII or Binary: This is important if you are planning to edit the data outside Petrel. In that case, you need to export the data in ASCII format. Properties: Some of the formats do not include the properties on export. In that case, you need to export them separately. Compatibility: Not all formats are supported by all simulators or third party applications. Check the available formats in the other application before exporting. File size: Some of the formats provide a higher efficiency compared to others, resulting in much smaller files. This will minimize both disc space requirements and the time needed to move files between systems (if you are running remotely). By default, the OPF (Open Petrel Format) format is used for all simulation runs. It supports curved and listric pillars, is binary and includes the properties. Note that ECLIPSE has to be 2005a version or later in order to read this format.



Advanced

Transmissibilities tab Use the Transmissibilities tab to: • Set a minimum pore volume • Compute transmissibility in Petrel and export to the simulator

Transmissibility and pore volume multipliers are written to the simulator deck.

Typically, the individual simulators have calculated the pore volume of cells, fluid transmissibility and thermal conductivity between them. These are straightforward calculations, dependent upon the grid geometry and properties and need only be calculated once prior to the first simulation step. The advantage of sending these to the simulator is that the set of connections and their strengths will be the same whichever simulator is being used. The transmissibility and pore volume values are sent from Petrel to the simulator as keywords or inside the GSG file when the option Calculate and export transm. and pore volumes is selected. FrontSim does not support this feature.



Exercises – Initialization of the model The next exercises show you how to initialize the model.

Exercise Workflow

• Initialize the model

Exercise Data In the following exercises, we will continue with the project we have made earlier. Alternatively, you may load the project Mod_3_ Completed.pet from Backup Projects folder.

Initialize model In this exercise, we will initialize the 3D model with fluid and rock physics functions. We will leave the development strategy field empty. Exercise steps 1. In the Processes pane, expand the Simulation folder and open the Define simulation case process. 2. Select Create new case and name the new case Simple. 3. Make sure the Simulator is set to ECLIPSE 100, and the Grid is set to Simple. 4. In the Grid tab, deselect the check boxes in front of Permeability and Porosity. 5. Enter a permeability of 1000 in the I- and the J- direction and of 50 in the K-direction. 6. Type in a porosity of 0.12.



7. Go to the Functions tab and select the Drainage relative permeabilities in the left panel by left-clicking it.

8. Drop in the saturation function Saturation function 1 that you imported in the Input pane (by selecting it) and clicking the blue arrow in the dialog.

9. Still in the Functions tab, select the Black oil fluid model from the list in the left panel. Reservoir Engineering


10. Ensure that the Initialize by equilibration option is selected. 11. Drop in the Initial condition 1 of the black oil model, Light oil + gas, that you created earlier. As you only have one region, there is no reason to use a region index property. 12. Select the Rock compaction function from the list in the left panel. Drop in the Rock compaction function 1 from the Rock physics functions folder in the Input pane. 13. The Strategies tab should be left empty as you are only initializing. If there is an empty row, delete it by selecting the row and clicking the Delete selected row(s) in table button 14. Click Apply to save the case. The case is saved to the Cases pane. 15. Click Run. ECLIPSE 100 is launched. Wait for the initialization of the case to finish. Once the run is finished, go to the Cases pane, right-click on the simulation case (ECLIPSE 100) and select Show print file. This will open the print file in your default text editor.

At the bottom of this file, you will find the initial fluid in place report. You can view the initial properties that are stored in the Simulation grid results folder on the Results pane. The next lesson explains how to view 3D data. 122 • Initializing the model


Lesson 2 – 3D Viewing 3D Viewing The simulator loads the results, and a folder Simulation grid results is added to the Results pane Three sub-folders : - Composite results - Static - Dynamic Use the Cases pane to select which simulation case to view

3D Viewing Time step animation Set current date and time of display. You can use the report steps available for the property. To view report steps, select to step by - Displayed


You can use the report steps from another property. Select to step by - Selection

You can specify the report steps. Select to step by - User Interval


3D results from simulation are accessible from the Results pane. The time player speed can be changed from the Project settings menu.

To display simulation results, you must select a property and a simulation case. If the property is time dependant, the time player is used to animate the display through time. In the folder Composite results, properties are stored as ternary properties (saturation), vectors, and tensors. The Static folder stores static input data to the simulators (INIT file). The Dynamic folder contains data from the restart file and these typically change with time.

3D Viewing 1D filters Right-click the property and select Create 1D filter... A 1D filter can be used to limit the range of cells displayed for any property.

Use the property from relevant case. Select the relevant report step.

The simulation grid results properties can be converted to grid properties, and will be stored in the Properties folder on the Models pane. This can be done to access more property operations, for example, map creation. 124 • Initializing the model

Right-click on a property in the Simulation grid results folder and select Create 1D filter. In the dialog that opens, you can drag the sliders to select the range of values you want to filter out. Here, you specify which simulation case the property is referring to and also which report step the filter should be applied to. The filter is stored on the Input pane under the Filters folder, and can be turned on and off.


3D Viewing I, J, K layer filter You can view all cells with the same I, J, or K index by pressing the filter symbol in the function bar.

The filter tools are available in the function bar when any of the property modeling processes are active.

3D Viewing Well filter Right-click on the Well filters folder and select Insert new well filter.


Specify top and base of the filter.


Right-click on the Well filters folder under the Wells folder on the Input pane to insert a new filter. In the dialog that opens, you can select which interval of the well trace you want to display. The filter applies to both well logs and traces. The new filter takes effect when the check box in front of it is selected.

User filters

Schlumberger Private

You can make filters interactively from function and histogram windows. In a histogram window, you can drag a section along the x-axis to specify the filter. The new filter will appear on the Input pane and can be applied to other properties. In the illustration above, the histogram window is used to make a filter for high values of porosity. This filter is applied in a 3D window to show oil saturation in high porosity cells. It is also possible to create a filter from a function window. For example, a cloud of data points can be selected from a cross-plot of two properties. 126 • Initializing the model


3D Viewing Ternary property display Select Saturation from the Simulation grid results (Composite results sub-folder). Activate Show/hide auto legend from the toolbar.

General intersection



Right-click on the Intersections folder on the Models pane and select Insert general intersection. An intersection plane is added to the folder. When the general intersection is displayed in the 3D window, the intersection toolbar appears. Click the Toggle visualisation on plane tool button to enable visualization on the intersection plane. Once this tool is activated, subjects with blue check boxes can be displayed on the intersection. Use the Manipulate plane plane.

tool from the function bar to drag the

Intersection window

The intersection plane can be turned into an intersection window.

Right-click the general intersection and select Create intersection window to display your general intersection in an intersection window. Select the check box in front of the subjects to put them into view. If you drag the general intersection in the 3D window, the intersection window is automatically updated. 128 • Initializing the model


Exercises – Results viewing In the previous exercise, you initialized the 3D grid. This exercise will show you how to display 3D properties. Exercise Workflow • View 3D simulation data • Use filters • Use of general intersection planes • The multi-value probe Exercise Data For this exercise, continue to use the project you used in the previous exercise.

3D viewing Your simple grid is now initialized and the initial properties are stored in the sub-folders of Simulation grid results on the Results pane. You can view any of the initial properties, such as saturation or pressure in a 3D window. The exercises demonstrate how to apply different filters for a better view. Exercise steps 1. Open a new 3D window. 2. Go to the Cases pane and select the relevant case. 3. Go to the Results pane, and expand the Simulation grid results folder. Then, expand the Dynamic sub-folder. Select to display Water saturation (SWAT). 4. Click the Show/hide grid lines button in the function bar to display the grid lines. If the icon is not on the function bar, activate the Define simulation case process on the Processes pane. 5. Click the Show/hide axis display the coordinate axis.

button in the menu bar to

6. Click the Show/hide auto legend button in the menu bar to add the legend to view. 7. To get a better view, you can apply filters. Right-click on Water saturation, and select Create 1D filter. 8. In the dialog, use the slider to select a minimum water saturation of 0.35. Click Apply, and observe the change in the Reservoir Engineering


3D window. Click OK to close the dialog. 9. Go to the Input pane, open the Filters folder and turn off the filter you just made.



Using I, J, and K filters in a 3D window There is a wide range of available filters you can use when you are viewing data in 3D. Exercise steps 1. Continue to work with the 3D window displaying the water saturation. 2. To make the I, J, and K filters available, activate the Define simulation case process from the Processes pane. 3. Click the Display the cells with same K button to view one K-layer at a time. 4. You can use the Step property forward/backward buttons / to go to another K-layer. 5. Click once more to cancel the K-layer filter. 6. Click the Toggle simbox view button to change to a view that flattens the model.

Making filters using a Histogram window You can make a filter based on data displayed in a histogram or a function window. The filter can be applied to data displayed in a 2D or 3D window. Exercise steps 1. Open a histogram window, and display the initial pressure 2. Click the Select using 1D range on x-axis button in the function bar. 3. Left-click in the histogram window and drag to select the values that should define the filter. Select only the largest pressure values to create a filter that exclusively displays the cells with high pressure. Reservoir Engineering


4. Go back to the 3D window that displays the water saturation. 5. Go to the Input pane and expand the folder Filter folder > User. 6. Select the Pressure filter, and observe the effect in the 3D window.



View data on an intersection plane You can insert a general intersection into the model and select to view data on it. The plane can be moved and tilted. Exercise steps 1. Use the 3D window displaying the water saturation, but turn off all filters. 2. Right-click the Intersections folder under your 3D grid (Simple) and select Insert general intersection. 3. Click the Clip in front of plane button in the General intersection player toolbar at the bottom of the user interface. 4. To view data on the plane, click the Toggle visualization on plane button on the intersection plane toolbar. 5. Items that you can display on the plane now have a blue box or a radio button. Select the box in front of Water saturation to view the saturation on the plane. 6. Click the Manipulate plane button in the function bar to move the plane to a different position. 7. Right-click the General intersection on the Models pane and select Create intersection window. 8. Select to display the water saturation in the intersection window. 9. Select to tile the intersection window and the 3D window by selecting Tile vertical from the Windows menu. 10. Move the intersection plane in the 3D window and notice how the intersection window is updated simultaneously.



Optional Exercise - The multi-value probe Sometimes it is useful to be able to view several property values in the same grid cell. The Multi-value probe gives you a tabular view of the grid properties. Exercise steps 1. Return to your 3D window that displays the water saturation and select to view the pressure. 2. Now you have an access to the Multi-value probe mode button in the function bar. 3. In the dialog that opens, add four rows by clicking the Append item in the table button . 4. Use the blue arrow in front of each row to drop the property into the dialog. Start with porosity from the fine grid. 5. In order to use the grid properties from the simulation results, simulation case need to be provided (see Input part of the dialog). Drop in the Simple case from the Cases pane as shown in the picture below. In the Results part of the dialog, drop in Porosity (PORO) from the Static sub-folder of the Simulation grid results. Then, from the Dynamic sub-folder drop in Water saturation (SWAT) and Pressure (PRESSURE). Note: these properties were taken from the first time step.

6. Left-click on any cell in the 3D window and observe how the table is updated to show the property values in that cell. Note that you can compare the property values between different grids by using this tool. 134 • Initializing the model


Summary In this module, it was demonstrated how to initialize a simulation case and how to inspect the initial 3D grid properties.



Module 5 - Upscaling Introduction In this module we will briefly cover how to convert a geological grid into a simulation grid. Geological grids can contain tens of millions of grid cells; however, a model that is suitable for simulation usually consists of 100.000 to one million cells, depending on the computer the simulations are run on. Consequently, a coarser, less detailed model is required. In addition, since the simulators are designed to work on orthogonal grids, the coarse simulation grid should be as close to orthogonal as possible. The first step is to coarsen the fine scale grid. To do this, you must first define the resolution in the x-and y-directions using the Pillar gridding process. Afterwards, the subdivision in the z-direction will be made using the Scale up structure process. Once the geometry of the coarse grid is defined, we will use the Geometrical modeling process to quality check geometrical properties of the coarse grid, such as grid cell volumes and angles. Finally, the properties from the fine grid will be re-sampled into the coarser simulation grid using the Scale up properties process. Prerequisites • Basic knowledge of Petrel is required. Learning Objectives In this module you will learn how to: • Make a coarse simulation grid based on a fine scale grid using the Pillar gridding and Scale up structure processes. • Compute geometrical properties such as cell angles and volumes for a 3D grid • Scale up properties from a fine to a coarse grid using the Scale up properties process Reservoir Engineering

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Lesson 1 – Grid Coarsening using the Pillar gridding process

Upscaling Workflow

1. Coarsen the fine grid in the x- and y-direction 2. Make a vertical subdivision of the coarse grid 3. Quality check the resulting 3D grid (cell angles) 4. Sample properties from the fine grid into the coarse

Coarsen the grid in the x- and y-direction Simulation considerations Cell size and shape

• Sufficient detail to describe flow • Number of cells small enough to run simulation

Grid orientation

• Permeability anisotropy • Fault directions Wells • Enough cells between wells

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You may find that there are conflicts between the different requirements of the simulation model. A description of the reservoir in sufficient detail, describing changes in saturation and pressure, may conflict with the maximum number of cells a simulator can do computations on in a reasonable amount of time. While a geological model can consist of tens of millions of cells, a typical desktop computer cannot perform simulations on models with much more than a million cells.

Making the Coarse Grid Two methods

Make simple grid

• Simple and fast • For models without faults • Can insert simulation faults

Pillar gridding

• Used to make 3D grids that adapt to faults

There are two ways to make a simulation grid using Petrel, the Make simple grid process and the Pillar Gridding process. Previously, we made a grid using the Make simple grid process, and were then able to insert vertical ‘simulation’ faults at the position of existing grid nodes. Simulation faults can be barriers to flow, but do not have throw, so they do not create communication between layers. You can introduce throw along simulation faults using the Edit 3D Grid process, but this is not recommended as the editing process is very time consuming and can be difficult to quality control. Use the Pillar Gridding approach if you have faults with throw, non-vertical faults or if you want the faults to define segments in your grid. The result of both of these processes will be a skeleton framework of the 3D grid that is ready to insert surfaces into. Reservoir Engineering

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Pillar gridding Overview

1. Create a grid adjusted to the mid-points of the Key Pillars.

2. Extrapolate the pillars to the top and base shape points. This will create a 3D grid of pillars, represented by the top, mid and base skeleton grids. Pillars will be created at every corner of every grid cell.

Pillar Gridding - Concept Pillar Gridding is the process of making the “Skeleton Framework” of a 3D grid that incorporates faults. The Skeleton is a grid consisting of a Top, a Mid, and a Base grid. Besides the three skeleton grids, there are pillars connecting every corner of every grid cell to each other. In the above slide, the figure to the right shows an example of the three skeleton grids and one intersection through the grid that shows the Pillars connecting grid cells together. When creating the Pillar Grid, you will work with the Mid Skeleton grid. The Mid Skeleton grid is the grid attached to the mid-point of the Key Pillars, which defines the fault planes (left figure). The purpose is to create a grid that has good geometrical properties at the Mid point level, with respect to grid cell size, orientation and appearance of the cells. The next step is to extrapolate this Mid Skeleton upwards and downwards in order to create the Top and the Base skeletons. This is done when you click OK in the Pillar gridding process dialog.

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Pillar gridding Terminology

Pillar Gridding - Terminology Boundary: Polygon, boundary segment or part of boundary Trends: Guidance for the grid and used as segment divider (where no faults) Faults and directions: Guidance for the grid (optional to set no fault or set no boundary) Segments (Regions): Compartment closed by faults or trends

Segments – (fault compartments) are areas that are enclosed by faults, grid boundary, trends or any combination of these. Segments are used in several processes in Petrel. For instance, different settings and filtering can be applied to segments, and volumes will be reported by segment when running the Volume calculation process. Segments are similar to the term ‘Regions’ used in ECLIPSE. Segments can be used to create different Fluid in Place Regions with different contact levels and fluid properties. Boundary – The boundary defines the extent of the model. You can use a polygon as input, or you can digitize the boundary. Faults can be set as part of the boundary. Trends – Trends can be used to orient the grid cells in a particular direction. Trends can be set outside of the grid to give an overall direction for the grid cells. The trends can define both I and J directions. Trends can also be used to connect one fault to another or they can be inserted between faults. Trends cannot cross faults. Trends can be used inside the model to separate areas into different segments. Faults – An area enclosed by faults will, by default, make out a segment of the model. If a direction is assigned to a fault, the grid is forced to be aligned with that fault. Reservoir Engineering

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Pillar gridding Cell shape

Make zig-zag type faults Gives a grid with cell angles close to 90°. Simulators assume right angles at cell corners.

Pillar Gridding - Settings • Give a name to the model or overwrite an existing model. • Enter the increment in I and J. The increment is given in project units. • If you are making a simulation grid, define zig-zag type of faults. As a general rule, the deviation from 90° should be less than 25 –30°, and the average less than 15°. • Once all of the settings are entered, click Apply. This will create the Mid skeleton grid. • When the Mid skeleton grid looks good, click OK and the pillars will be extrapolated upwards and downwards in order to create a Top and a Base skeleton grid.

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Pillar gridding

Cell shape and orientation To create a simulation grid with orthogonal cells, the number of trends and directed faults in the grid should be kept to a minimum. Use zig-zag faults Use trends OUTSIDE the boundary to get zig-zag faults AND the correct grid orientation, or set the orientation in the process dialog.

You must choose whether some faults should define a direction in the grid. For a simulation grid, the fewer the better, as this will allow the algorithm to make orthogonal cells. The default grid orientation is North-South. To change this without making a fault into a directional trend, create a trend outside the area of the grid. By doing this, you can give a direction to the grid, and still ensure that all faults are zig-zag. Alternatively, go to the Expert tab on the Pillar gridding process dialog and specify the rotation angle.


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Pillar gridding Cell size

I and J increment Gives the average cell size, and hence the model size The cell size specified is an average – cells will vary in size as the gridding honors faults

One of the many aspects to consider when setting cell size is the effect of numerical dispersion. Numerical dispersion is due to the discretization of the volume into cells with properties at the center. Water is injected into Cell 1 and as soon as the critical water saturation is reached, water will be able to move to Cell 2. Once water is mobile, it will advance in every time step, no matter the length of the time step. This creates a smeared out water saturation front, instead of the correct sharp displacement front. One way to reduce the effect is to have smaller cells. If the model contains cells with a small volume, this could cause the time required for the simulator to increase. It is possible to select to set such cells inactive. If the total volume of all such cells is significant, consider redoing the gridding.

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Throughput related problems

You can set a threshold value for pore volume. Cells with a smaller pore volume will be set inactive.

Once your simulation case is initialized, the pore volume property is stored in the Static sub-folder of the Simulation grid results folder on the Results pane. If this property shows that you only have a few cells with a small pore volume, you can select to set those cells inactive to avoid throughput problems and increased simulation time. Select the Advanced>Transmissibilities tab of the Define simulation case process and type in the minimum pore volume. On this tab, you can also set max pinch-out thickness for no-neighbor connections to be generated. Notice that the export of transmissibilites and minimum pore volumes from the Define simulation case process is not supported by FrontSim.


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Pillar gridding Faults tab

You can select to remove faults

In the Faults tab: 1. Select Selected faults/trends 2. Deselect All faults 3. Select/deselect faults in list 4. Click Update visible from lists

Faults can be excluded from the Pillar Gridding process by turning them off on the Faults tab of the process dialog. You must click the Update visible from lists button to see the effect in the 2D window.

Pillar gridding

Pillar geometry and grid formats Select a simple pillar geometry for simulation grids Five types of geometry files can be created for simulation: .OPF – most flexible, incl. curved faults, binary .GRID – incl. curved faults, binary .EGRID – straight line faults, binary .GRDECL – straight line faults, ASCII .GSG – incl. curved faults, binary

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The more complex the pillar geometry, the more accurately the cells will honor volumes on either side of faults. However, the cells will be less orthogonal. Notice that the grid formats GRDECL and EGRID (uses the ZCORN and COORD keywords) only supports vertical and linear faults. If you use listric or curved faults in your Petrel project and export the grid to the simulator in one of these formats, the grid will be distorted. Refer to the Initialization lesson in Module 4 for more information on the grid formats.

Pillar gridding Result

The result of the Pillar gridding is a skeleton grid. The skeleton grid consists of a top, a mid, and a base skeleton, representing the top, mid and base shape points of the Key pillars, respectively. Along and between all of the faults are a set of pillars, evenly distributed based on the given increment in the I and J direction. This defines the framework, including the faults and the cell size, that the surfaces can be inserted into. As no surfaces are inserted yet, there are no 3D grid cells at this stage. Reservoir Engineering

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Exercises – Grid coarsening You are provided with a 3D geological scale grid with properties, which should be coarsened for simulation purposes. The Pillar gridding process is a key part of building a 3D grid. This is where the size and geometry of each cell will be set. The steps outlined below do not cover all the functionality available in Pillar gridding. Further information is available in the Online Help. Exercise Workflow • Make the coarse grid using the Pillar gridding process • Change grid orientation Exercise Data In this exercise, continue to use your project from the previous exercise.

Grid coarsening using the Pillar gridding process Exercise steps 1. Open a 3D window, go to Petrel RE 2010 folder in the Models pane and display the Fault model.

2. Single-click on the Petrel RE 2010 model (remember to always click on the icon of an object) to make it active – bold. Operations in Petrel are done on the active item, not on items displayed in a window. 148 • Upscaling


3. Double-click on the Pillar gridding process under Corner point gridding in the Processes pane. Ensure the top border of the Pillar gridding process dialog reads Pillar gridding with ‘PetrelRE2010/Fault model’. You will be prompted with a 2D window displaying the faults from the fault model as illustrated below. Inspect the Models pane and make sure that only objects from the active model are visualized. 4. You need to specify a boundary for your reservoir. In this exercise, we will use the boundary that was made for the fine model. Expand the Fault model and notice that it has a boundary.

5. In the Settings tab of the Pillar gridding process dialog, select Create new. Name the grid Upscaled. Change the Increments to 350x350 m, and select Make zig-zag type faults.


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6. On the More tab, select the Vector field method (utilizes FloGrid algorithms for I/J assignment). 7. In the Geometry tab, make sure Listric and Curved faults are deselected, both in Non faulted pillar geometry and in Faulted pillar geometry. This ensures that the final grid will only have linear pillars. 8. In the process dialog, click Apply. Petrel will attempt to build the mid skeleton grid with the parameters you have specified as illustrated below. Note that there is a direction assigned to one of the faults causing the grid to be directed along that fault.

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Changing the grid orientation Often a specific grid orientation is thought to be better for simulation purposes. In this exercise, you will learn how to set the grid orientation. Exercise steps 1. To remove the direction from the fault, first select the fault that is colored green by left-clicking it. Then click the Set arbitrary direction button in the function bar. 2. Click Apply to see the effect. The grid should now have the default north-south direction. 3. To change the orientation of the grid, simply insert an I or J trend line outside the grid using the New I-trend or the New J-trend button (left-click to start and double-click to end the trend line). Trends can be deleted by selecting them and pressing Delete on the keyboard. Click Apply to see the effect once you have added a trend. Reservoir Engineering

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4. When you are happy with the mid skeleton grid, click OK in the process dialog. Accept the generation of lower and upper skeleton grids by clicking Yes. Examine these in the 3D window. 5. Save the project. It is possible to only use a sub-set of the faults in the simulation grid without removing any data from the original Fault model. You can remove faults from the simulation model in two ways:

a. Turn them off in the Faults folder under the Fault model in the Models pane. 152 • Upscaling


b. In the Faults tab of the Pillar gridding dialog, select Grid with selected faults/trends. Then, deselect the All Faults check box. You can now specify which of the faults in the list you want to include in the 3D grid. Click the Update visible from lists button to update the 2D window.

Lesson 2 – Vertical coarsening –the Scale up structure process

Vertical subdivision

Stratigraphic Model

Simulation results will be different! Sim Model 3

Sim Model 2

0

Sim Model 1

Permeability, mD

1000

A fine scale geological model can be represented by models of different resolution for simulation. It is important for the simulation models to keep the main characteristics, such as horizontal flow barriers, of the original model.


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Vertical subdivision Two methods

Based on input data Use the Make horizons, Make zones, and the Layering processes Based on the fine model Use the Scale up structure process

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There are two ways to subdivide the simulation grid in the vertical direction. Based on input data – Use the Make horizons, Make zones, and the Layering processes to do the subdivision based on the available input data such as surfaces, seismic interpretations, and isochore data. This type of vertical subdivision is usually done as part of the geological structural modeling process; further details are covered in the Structural modeling course. Based on the fine model – Use the Scale up structure process as shown in the illustration on the slide. In this case, a fine grid is given as input to the process and then the layering of the simulation grid is done by using information on the layering of the fine grid. This procedure will be explained in the following slides.

Scale up structure Settings for each zone

Specify the type of layering in each zone. Specify the number of layers in each zone. You can combine two zones into one by clicking Remember to update the Top and Base horizon of your new zones.

Settings for each zone - Once a fine scale model is inserted into this interface, the bottom panel is populated with the vertical layering scheme of the fine model. You must then do the required edits to produce a coarser vertical layering. Select the settings with great care to make sure that important features of the fine model are captured, such as a sealing layer. Reservoir Engineering

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In this panel, you also specify the zonation of the coarse grid. It is possible to combine two zones in the fine grid into one zone in the coarse grid. To do so, delete one of the rows in the table. Then, insert the correct top and bottom horizon on the remaining zones by selecting them in the Input pane and dropping them into the table by using the blue arrow. For each zone, you must select the type of zone division; proportional, follow base, follow top, or fractions. Finally, specify the number of layers or layer thickness within each zone.

After the grid is built, and before the properties are upscaled, the grid geometry should be checked. Cells which deviate considerably from orthogonal, have small volume cells next to large volume cells and badly distorted cells, can have a negative impact on the simulation. If errors are encountered as a result of poor grid geometry, the simulation time may increase considerably or may not complete at all. Use the simulation report to identify problems related to cell geometry. Cells which cause problems can be set as inactive (ACTNUM=0). If problems are severe, the grid should be rebuilt.

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Cell angles

Cell angles - Where faults have been set as I or J trends, the grid may become distorted and cells deviate considerably from being orthogonal. Compute the geometrical property Cell Angle and use the property filter to identify cells with angles that are far off from 90 degrees. The values calculated are angles representing the maximum deviation from 90 degrees at each corner. As a rule of thumb, values less than 15 are good for simulation. Higher values can result in errors when used in a typical five-point difference scheme. However, distorted cells may not be so important in regions that are not significant for flow (e.g. inactive cells or aquifer regions). Create 1D filters - To get a better view of where a property takes on values in a particular range, right-click on the property and select Create 1D filter. Use the sliders to specify the values you want to filter out. The new filter is stored in the Filter folder of the Input pane. Reservoir Engineering

Remember to select Create new property if you are running the Geometrical Modeling process to create several new properties. Petrel will, by default, select to overwrite an existing property. Upscaling • 157

Cell inside-out

Cells close to faults may become so distorted that they sometimes can turn ‘inside out’, where one axis is pushed through a different face. These generally do not visualize well, but can be isolated by using the property filter to remove the cells which deviate from 0 (normal). The cell inside-out check just gives a flag to indicate errors. If it is zero everywhere, the grid is OK.

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Exercises – Vertical coarsening and grid quality check In the previous exercise, you specified the coarse grid layout in the x- and the y-direction. The next step in the coarsening process is to specify the vertical subdivision. In this exercise, the layering of the coarse grid is done based on the layering in the fine grid using the Scale up structure process. After the grid has been subdivided in the vertical direction, you can check the geometry of the grid cells by computing cell angels and volumes. Exercise Workflow • Use the Scale up structure process to specify the layering of the coarse simulation grid based on the layering of the fine grid. • Check the geometry of the resulting grid, in particular check for bad cell angles and twisted cells. Exercise Data In this exercise, continue to use the project from the previous exercise.

The Scale up structure process The layering should be done with care. Do barrier layers in the fine model need to be kept as separate barrier layers in the upscaled model, or can you combine these into a thick layer together with other layers? How can you preserve the lateral and vertical heterogeneities? It is important to keep the fine model (the geology) characteristics. This is done by keeping more of the layers separate. However, it will always be a compromise between fewer cells and keeping the level of detail. Exercise steps 1. Make sure the upscaled grid you created in the Pillar gridding process is active (bold) by clicking on its name. 2. Double-click the Scale up structure process in the Upscaling folder of the Processes pane. 3. Expand the Petrel RE 2010 model and click on Fine grid. Reservoir Engineering

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4. Click on the blue arrow in the Scale up structure process dialog to insert this grid as the Input grid. When this is done, the layering in the fine scale model is displayed in the lower part of the window. 5. There are three zones in the input grid. We are going to specify two zones in the coarse grid. Left-click on the symbol in front of Zone 1, then click the Delete selected row button.

6. Rename the two remaining zones Top and Base, respectively. 7. Go to the Models pane, select the Top reservoir horizon under the Horizons folder of the Fine grid, and drop it in as the Top horizon of the zone Top. 8. Select proportional layering for both zones. 9. Select to use 5 layers in the Top zone, and 3 layers in the Base zone. 10. Press OK to run the process. 11. Select to view the Edges of your Upscaled grid in a 3D window to see the resulting layering. Save the project.

Grid quality check Quality checking of the grid should be a continuous process during the upscaling process. This includes checking the grid for cells with small volume or with angles that deviate too much from 90 degrees. Exercise steps 1. Activate the upscaled grid (make it bold). Petrel processes 160 • Upscaling


apply to the highlighted grid, which may not necessarily be the same as the one displayed in the 3D window. 2. In the Processes pane, open the Property modeling folder and double-click on Geometrical modeling. The process dialog header (at the top of the process dialog) shows which 3D grid you are working on. 3. Ensure Create new property is selected. 4. Use the drop-down list Select method to select the method Cell Volume. Accept the default property template.

5. Click Apply. You now have a new property called Bulk volume in the properties folder in your active 3D grid. The property gives the bulk volume for each individual cell. Right-click on the Bulk volume property, select Settings and inspect the Statistics tab to check for negative/small cell volumes. 6. Repeat the two steps above with Cell Angle and Cell Inside Out as the method. Remember to select Create new property each time and to select an appropriate template. The Cell Angle property gives the deviation from angles of 90 degrees for each cell. If the Cell inside out property is different from zero, the cell is twisted. 7. Examine the new properties located in the Properties folder in a 3D window. You may need to reset the color scale. First select to view the color legend by clicking the Show/hide auto legend button in the top tool bar. Then, click on the Adjust color table on selected button .


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Using value filter You can filter the grid on properties to see only cells with extreme values for each of the geometrical properties. Exercise steps 1. Display the Cell angle property in a 3D window. 2. To create a value filter, right-click the Cell angle property and select Create 1D filters. 3. Use the sliders to make a filter where you only see the largest values.

4. Click Apply. 5. Go to the Input pane. Note that you can turn the filter on and off from the Filters folder. Save the project.

162 • Upscaling


Lesson 3 – The Scale up properties process

Upscaling Workflow

1. Coarsen the fine grid in the x- and y-direction 2. Make a vertical subdivision of the coarse grid 3. Quality check the resulting 3D grid (cell volumes, cell angles) 4. Sample properties from the fine grid into the coarse


Upscaling • 163

Scale up properties Select the property or the folder of properties to scale up by leftclicking in the Models pane. Click the blue arrow in the Scale up properties process dialog to drop in the selected property.

You need to select the properties to scale up. You can select any property from a Properties folder on the Models pane, not only from the grid that was used for the structural upscaling. Multiple properties can be scaled up in one run.

164 • Upscaling


Scale up properties Expand the fine grid inside the Scale up properties process dialog. You can scale up many properties in one go.

Once you have selected the properties to scale up, a folder for each input grid is add to the process dialog. To access the settings for each property, you need to expand the folder for the 3D grid, and then left-click the property. The coarse grid cells to populate can also be restricted by enabling the Upscale to filtered cells only option. This will restrict upscaling to those output grid cells, which are included in the currently active filter.


Upscaling • 165

Scale up properties

Select algorithm for each property Left-click one of the properties from the fine grid to access the settings available.

An algorithm must be selected for each property. Left-click each of the properties to make it active. Then, select an algorithm from the drop-down menu. For scalar properties there are three algorithms to select from: Averaging (volume-weighted) – This algorithm computes an average of the property value of the fine grid cells, using the volume of each cell as weight. Averaging (cell count) – This algorithm computes an average of the property in the fine grid cells with the same weight on each input cell no matter its size. Summation – Computes the sum of the property value in all fine grid cells that contribute to the value of a coarse cell. This method should only be used to scale up volumes. In addition to those three algorithms, there are two more available to scale up permeability: 166 • Upscaling


Directional averaging – Gives the user the possibility to use different averaging methods in different axis directions. Flow-based upscaling – This is an algorithm where a flow simulation is run over all fine cells making out each coarse cell to estimate the total permeability in each axis-direction of the coarse cell.

Scale up properties

Several methods available for each algorithm

Averaging methods For all continuous properties, select between the methods: • Arithmetic mean - Used for additive properties such as porosity, saturation, and net/gross. x a =

1 n ∑ xi n i =1

• Geometric mean – Normally a good estimate for permeability. It is sensitive to lower values: x g = n ∏ in=1 xi • Harmonic mean – Gives the effective vertical permeability if the reservoir is layered with constant value in each layer. It is Reservoir Engineering

Upscaling • 167

sensitive to lower values: x h =

n

∑

n

i =1

• RMS (quadratic mean) -

xr =

1

xi .

1 n 2 ∑ xi n i =1 .

• Minimum – selects the lowest value. • Maximum – select the highest value. • Power – The user must specify the power ‘p’. If p=-1, this method is equal to harmonic mean, if p=2 it is equal to RMS.

xr =

p

1 n p ∑ xi n i =1

For discrete properties, the choice of algorithms is different: • Most of. Assigns the value that occurs the largest number of times. • Minimum. Assigns the minimum value. • Maximum. Assigns the maximum value. • Arithmetic. Computes the arithmetic mean.

168 • Upscaling


Algorithm

Permeability – directional averaging Input: Specify each of the input components. Those can all be the same. Output: Three permeability components.

Directional averaging methods for permeability Permeability is different from other grid properties in the way that the value in a cell is dependent on the value in neighboring cells. Therefore, there are more methods available for permeability than for other properties. • Arithmetic-harmonic – for each coarse grid cell, the fine cells in each plane perpendicular to one of the axis direction are arithmetically averaged to give an approximate permeability for that plane. The plane permeabilities are then harmonically averaged to give the permeability for the coarse grid cell in that axis direction. This is repeated for each of the I, J and K directions to produce the three different output permeability properties. • Harmonic-arithmetic – This method works in the same manner, only in this case the harmonic averaging is computed first, then arithmetic. • There is also Arithmetic-Power, and Power arithmetic. These methods work as the two methods explained above, only power averaging is used instead of harmonic. Reservoir Engineering

Upscaling • 169

Note that harmonic mean gives more cells with low values than arithmetic mean does. Therefore, harmonic mean is commonly used to upscale permeability for which it is important to capture cells with low values.

Exercises – Scale up properties In the previous exercise, you completed the 3D grid. In this exercise, you are going to sample properties from the fine grid into the coarse grid. To do so, you need to instruct Petrel on which fine grid to sample properties from. You also need to specify which properties to re-sample and by which upscaling method. There are several averaging methods available in Petrel. Each method gives you a slightly different result. For instance, a harmonic mean puts more weight on small values than an arithmetic mean does. Flow based upscaling will assign permeability in the upscaled grid that reflects the flow in the fine grid. Finally, you must tell Petrel which of the layers in the fine grid should contribute to each of the layers in the coarse grid. 170 • Upscaling


Exercise Workflow

• Select which grid to sample properties from • Specify which layers in the fine grid should contribute to each of the coarse grid layers when properties are upscaled • Select which properties to scale up and by which method • Quality check the results

Exercise Data In this exercise, continue to use the dataset from the previous exercise.

Scale up properties Exercise steps 1. Make sure the Upscaled[U] 3D grid you created is active (bold). 2. Open the Scale up properties process which is located under Upscaling in the Processes pane. 3. You need to specify which properties to scale up. Select Permeability and Porosity from the Properties folder of Fine grid in the Models pane and drop them into the process dialog by clicking the blue arrow.

4. Select the Porosity property by left-clicking it. 5. Use Averaging (volume weighted) as algorithm. 6. Select Arithmetic as Method.


Upscaling • 171

7. Left-click the permeability property, and select to use Directional averaging as algorithm. 8. Select Arithmetic-Harmonic as the averaging method.

9. Notice that the permeability property has now turned into a folder in the list in the process dialog. Expand the folder.

10. Select either of the components of Permeability by leftclicking it. 11. Select the correct input for each of the permeability components. Use Permeability for the I- and J-direction and PermK for the K-direction. 172 • Upscaling


12. Click OK to scale up permeability and porosity.

Apply different methods Exercise steps 1. Open the Scale up properties process again. 2. Notice how the settings for the properties that you have already upscaled are preserved and listed in the process dialog. 3. Also, notice how the Calculate setting is deselected. This means that as you add new properties to the dialog and click Apply, only the new ones will be computed. 4. Select Permeability and Facies from the Fine grid on the Models pane and drop them into the process dialog.

5. Left-click on the Permeability property that you just added to the process dialog. 6. Select to use Averaging (volume weighted) as the algorithm, and Harmonic as the Averaging method. 7. Enter a name for the new permeability property. Reservoir Engineering

Upscaling • 173

8. Left-click the Facies property. 9. Select to use Averaging (volume weighted) as algorithm, and Most of as Averaging method. 10. Click OK to scale up the properties.

Review the upscaled properties Exercise steps 1. Open a function window.

2. Select Permeability_I (arithmetic-harmonic) and Perm_ harmonic (harmonic). Harmonic average will usually honor the lower values more than arithmetic-harmonic. Observe this trend in your plot. 3. Open a histogram window and select to view the upscaled permeability properties along with the fine grid property. 174 • Upscaling


4. When you work with histograms, note that you can toggle between comparing the number of cells or percentage of cells by clicking the Use percentage in Y-axis button in the function bar. It is useful to compare percentage of cells when you compare values from the fine grid with values in the coarse grid. 5. Also you can select to volume weight the cells you are viewing by pressing the Weight histogram with volume button .

Review upscaled properties in a 3D window Exercise steps 1. Open a 3D window. 2. Select to view the facies property on your upscaled grid. 3. Click the Multi-value probe mode button in the function bar. 4. In the dialog that opens, drop in porosity from both your fine and your upscaled grid along with the facies property from your upscaled grid. 5. Left-click both in the channel and floodplain cells and compare porosity values.

You can make a CDF -curve (cumulative distribution function - curve) by pressing the Show cdf-curve icon or you can display a line between the histogram bars by pressing the Show lines between the columns icon . Both tools are in the Function bar.


Upscaling • 175

176 • Upscaling


Summary In this module we have upscaled a model from geological scale to a simulation grid. First, we did the coarsening in the horizontal direction using the Pillar gridding process. Next, we specified the layering of the coarse model using the fine grid layers as input. Using Geometrical modeling, we checked the coarse grid for poorly shaped and small cells. Finally, properties were scaled up to the coarse grid from the fine grid.


Upscaling • 177

Module 6 - Local grid refinements and Aquifers Introduction In this module, you will learn how to add local grid refinements and aquifers to your simulation model. Aquifers are used to model the pressure support from water or gas on the edge of a model. In Petrel, such processes are modeled using the Make aquifer process. It is useful to refine the grid in areas of fast flow, and this feature is available through the Make local grids process. Prerequisites Basic knowledge of Petrel is required for this module. Learning Objectives In this module, you will learn how to: • Add local grid refinements • Model aquifers


Local grid refinements and Aquifers • 179

Lesson 1– Local grid refinements

Local grid refinements

To better model fluid flow behavior, local grid refinements allow for a finer resolution of parts of the 3D grid. Transmissibility between the local grids and the global model are computed automatically by ECLIPSE/FrontSim. The properties of the cells in the refined grid cells can be inherited from the global grid or specified explicitly for the refined cells. The Make local grids process is available from the Corner point gridding folder in the Processes pane. Local grids are defined using wells, surfaces, and polygons as input.

180 • Local grid refinements and Aquifers


Local Grid Refinements

Choose to create a new LGR set or edit an existing LGR set.

A set contains a number of local grids. Each set is stored as a folder on the Models pane.

The areas that should be refined can be selected using: Wells: You must specify a radius. All cells that have their center closer to a well than the specified radius are refined. Polygons: Petrel computes the vertical Z-projection of the polygon with the host grid and selects all of the cells in the uppermost layer whose centers lie within the polygon. The polygon must be closed. This set of cells is then projected down through the layers (K-index) to produce a cell set. Surfaces: When surfaces are used as input to the Make local grids process, the cells that are refined are found by examining the distances between the cell-centers and the surface in a direction normal to the surface and around the edges. If the distance is less than the source influence distance, the host cell is added to the set.



Specify host cells from sources

Host cells Select the sources: Wells: Make a refinement around the well. Polygons: Make a refinement inside the polygon. Surfaces: Make refinements above or below. Click the blue arrow to add sources to the gridding process.

Refinement Method Select a source or folder of sources in the source list, and then select refinement method. Cartesian : Give number of fine cells inside each coarse cell Cartesian Gradual : The coarse cells are refined gradually. Finest resolution in the middle. Give number of levels.

Illustration: Cartesian gradual refinement with 2 levels.



Cartesian Nx,Ny,Nz: You specify the number of subdivisions required in each grid direction (Nx, Ny, Nz) and each host cell in the host cell set is sub-divided equally. Cartesian Dx,Dy,Dz: You specify the maximum size of the subdivisions required in each grid direction (Dx, Dy, Dz). Each host cell in the host cell set is sub-divided equally using the closest value to that requested. Cartesian Gradual Nx,Ny,Nz: Similar to the Cartesian Nx,Ny,Nz method, except that Petrel gradually increases the refinement degree towards the local-grid source over a number of levels specified in Levels. The parameters Nx, Ny, Nz thus represent the target number of subdivisions (in each grid direction) within the highest-refinement level (i.e., closest to the source). The method is available when surfaces or wells are given as input. Cartesian Gradual Dx,Dy,Dz: Similar to the Cartesian Dx,Dy,Dz method except that Petrel gradually increases the refinement degree towards the local-grid source over a number of levels specified in Levels.

Set source parameters Select a source or folder of sources in the source pane, and then set the selection parameters. Zone and Segment filters: Limit the refinements to some zones/segments. Grid separate zones: Creates a separate local grid in each zone. Source influence distance: Distance from well or surface that is refined.

Click the Display host cells button to see the cells in the 3D viewer that will be selected for local gridding.



Zone filter: You can select which zones should be included for grid refinement. This selection is also used when Grid separate zones is selected. Similarly, you can use the Segment filter to only generate grid refinements inside some of the segments. Grid separate zones: Non-gradual refinement methods only. Select this if you want to create separate local grid sets for each zone. Use active filter: Select this if you want to restrict the local grids to the host grid cells that are currently displayed.

Extending host cell along I, J, K The local grid can be made more or less regular in shape by extending it along the I, J, or K direction

No extension

An extended grid may have: • Fewer surface cells – thus, fewer connections to the coarse grid. Less work for the simulator. • More cells in it – the more cells, the more work for the simulator

Extended in K

When local grids are exported to the ECLIPSE simulators, they are decomposed into cuboids (in I,J,K). You can reduce the number of cuboids by extending a host cell set in any, or all of the I, J or K grid directions. This will generate larger host cell sets, but fewer cuboids in their decompositions. You must choose between these issues so that it generates an acceptable simulation.



Grid to well connections

Only cells with connections are refined

Choose this option for a selected well if you want to restrict the active source to open well–grid connections only (for example, perforations and open-hole sections).



Set different parameters for different sources By default, cell selection and gridding parameters are the same for all sources.

To change settings: • Select a source • Deselect Use default • Specify individual settings


The source panel displays a summary of the parameters for each source.


The two images above illustrate that a local grid cell gets the same property value as the coarse cell. This does not apply for geometrical properties such as cell volume or cell angle.

Upscale properties If the Use property filter option is on, Petrel will only upscale onto the grids that are visible.

• Select property in the fine grid • Display only the local grid • Use property filter • Deselect Ensure all cells get values

You can use the Scale up properties process to scale up a property onto the local grid set. To do so: • Display a property in a 3D window • In the Models pane, deselect to view the Global grid so that only the local grid set is displayed • Open the Scale up properties process and select which of the fine grid properties to scale up • Select Use property filter and deselect Ensure value in all cells



Grid coarsening 1. 2. 3.

Use polygon Select generation method – Coarsen Specify settings

Cells can be amalgamated to reduce the total number of active cells in the global grid. Coarsening sets must not overlap one another, but they can be joined together. Local grid refinements cannot be placed within or adjacent to a grid coarsening; that is, the local grids can only be applied to non-coarsened cells. Petrel sends the original fine model to the simulator together with the generated geometry for grid coarsening (COARSEN keywords).



LGR - Export 1. 2.

Make the local grid set active (bold) by clicking on its name. Right click the global grid set and select Export…

By default, properties do not get exported with LGRs. ECLIPSE will apply host cell properties to LGRs.

To export a local grid set, it must be highlighted (bold). It is not necessary to display the local grid set. Local grid properties are not exported explicitly; ECLIPSE will read the local grid keywords and apply the host cell properties. The export formats that support local grid refinements are: • Open Petrel Format (OPF) (Binary) • GSG (Generic Simulation Grid) • ECLIPSE Grid keywords (grdecl) (ASCII) • VIP Grid keywords (grdecl) (ASCII) The CARFIN keyword is exported to set up a Cartesian local grid refinement. It specifies a cell or a box of cells identified by its global grid coordinates I1-I2, J1-J2, K1-K2 to be replaced by refined cells. The dimensions of the refined grid within this box are specified as NX, NY, NZ.



Exercises– Local grid refinements Local grid refinements allow for a finer grid resolution near wells or in a region to better model fluid flow behavior. The Petrel workflow permits you to create local grid sets inside polygons, around wells, and close to a surface. The Define simulation case process only allows you to include one Local grid set, so all local grids required for the simulation need to be within this set. You can return to the Make local grids process and add or remove local grid definitions as required. Exercise Workflow • Import a polygon • Make a local grid set • Inspect the local grid set • Optional – Upscale property to the refined grid Exercise Data In the following exercise, we will continue with the project we made in the previous exercises. Or you can use backup project Module_5_ Completed.pet.

Import a polygon Exercise steps 1. Right-click in the Input pane and select Import(on tree) and import the file ImportData>Local grid>LGRpolygon. Make sure the file type General lines/points (ASCII) is selected. 2. Click OK in the dialog. 3. In the Input data dialog: select Generic boundary polygon as Line type, then click OK. The polygon appears at the bottom of the Input pane.

Make a local grid set Exercise steps 1. Activate your upscaled 3D grid. 2. Expand the Corner point gridding folder in the Processes pane. 3. Double-click on the Make local grids process. 4. Make sure Create new is selected. 5. In the Input pane, expand the Wells folder, then expand the 190 • Local grid refinements and Aquifers


6. 7. 8. 9. 10. 11.

Producers folder. Select the wells P03, P04, and P05 and drop them into the process dialog by clicking the blue arrow . Click the polygon you imported (in the Input pane) and drop it into the process dialog by clicking the blue arrow . Select the Polygons folder in the Make local grids process dialog. Select the method Cartesian Dx, Dy, Dz and set Dx/Dy to 100. Set Dz to 10. Select the Wells folder in the Make local grids process dialog. Select the Cartesian Gradual Nx, Ny, Nz method. Enter a refinement of 3x3x1 and type in 2 Levels for the wells. Select a Source influence distance of 600.

12. Open a 3D window and display the wells, the polygon you imported, and the porosity property from the upscaled grid. Select to show the grid lines by clicking the Show/hide grid lines button in the function bar.



13. Press the Display host cells button in the process dialog. The grid cells that will be refined are displayed in the 3D window. 14. Increase the Well influence radius to 800 and click on Display host cells again to see the effect. 15. You do not create any refinements until you clcik Apply or OK. You can continue to experiment with the settings.

16. Select well P05 in the Source name list of the process dialog and then deselect the Use default check box. Now, you can adjust the settings for this particular oil producer. Change the method to Cartesian Nx, Ny, Nz and the Source influence distance to 500. 17. Click OK to generate the local grid set.

Inspect the local grid set

The local grids have a yellow tick box. This means they can be used as a filter in Petrel similar to the Zone, Fault and Segment filters under the 3D grid. The filter can also be used with the Property calculator.

Exercise steps 1. In the Models pane, under the active 3D grid, you will now have a folder called Local grids. 2. Expand the Local grids folder. Right-click on Local grid set 1 and select Settings. Change the name on the Info tab to Wells and Polygon. 3. Click on different properties in the model; note that the local grids have inherited the host cell properties, with the exception of geometric properties and simulation results. Geometrical properties must be computed for the local grid cells, and simulated properties are only available if the simulation was run with local grid refinements.



4. Save the project. Normally, when you are using the Property calculator, turn off any local grids under the active grid or turn off the Use filter option in the Property calculator. Local grid cells will then inherit the properties from host cells. The local grid cells will display a grey color if they have not inherited the host cell properties (which is the case if they have been included in the filter settings in some way).

Upscale property – Optional In this exercise, you will upscale a property onto the local grid that you have created without re-upscaling the entire grid. As a result, any corrections that may have been made to the global grid will not be changed by this new upscaling run. It is always wise to make a copy of the properties you intend to update. Exercise steps 1. Click on the porosity property in the Properties folder of your coarse (upscaled) grid, then use the copy and paste functionality on the toolbar. 2. Give the new porosity property the name Porosity_lgr. 3. Ensure the property Porosity_lgr is displayed in the 3D window. 4. Deselect to view the Global grid under the Local grids folder. 5. To scale up the porosity to the local grids, open the Scale up properties process under Upscaling. 6. Left-click the Fine grid in the process dialog. Reservoir Engineering


7. In the Target cells part of the dialog, select the check box in front of Upscale to filtered cells only.

8. Left-click the Porosity property in the process dialog. 9. Select Porosity_lgr from the Edit existing drop-down menu.

10. Make sure that Calculate is selected for Porosity_lgr and that Ensure all cells get value is deselected. 11. For all the other properties make sure Calculate is deselected. (See tool-tip for more information).

If you do not want to upscale all of the properties from the fine grid to the local grid (for example, you only want the Porosity to be upscaled) be sure that No is selected in the “Calculate” column of the Scale up properties dialog. In this case, you will upscale only the Porosity. Compare both of the porosity properties by toggling between them. The only difference should be between the properties on the local grids. 194 • Local grid refinements and Aquifers

12. Click OK to scale up porosity to the local grid cells. 13. When the process is completed, select the check box in front of the Global grid in the Local grids folder on the Models pane. Reservoir Engineering

Lesson 2 – Aquifers

The illustration shows cells that are connected to an aquifer. In this case, the aquifer is placed underneath the reservoir and along the grid edges to simulate pressure support from water.


Make a folder of aquifers in order to use multiple aquifers in the simulation run. The Define simulation case process has only one place for aquifer input.


Make aquifer Choose to create a new aquifer or edit an existing aquifer. Select type of aquifer model • Numerical • Carter Tracy • Fetkovich • Constant flux • Constant pressure gas • Constant pressure/head water • Rainfall Each aquifer model is stored in the Aquifers folder on the Models pane under the parent grid.

The Make aquifer process is located under Simulation in the Processes pane.



Connections Select model. Enter area of interest: Use the Make/edit polygons process to define the boundary polygon.

First, specify which model to use. Then, specify the area that should be influenced by the aquifer. This is done by supplying a closed polygon. The polygon can be made using the Make/edit polygons process. You can drop in multiple polygons defining the connection areas of interest. Each of the polygons have individual settings for creating a unique drive direction for each area of interest.



Independent polygon areas and drive direction

Use the compass to define drive directions, the connections the aquifer will have to the grid. The direction of the aquifer can be: • Top down • Bottom up • Grid edges • Fault edges

Fault edges connection

Bottom up connection

After the area of interest is specified, you must select the drive direction and the vertical extent. If Bottom up is selected, the aquifer is connected to the bottom edge at the bottom of the reservoir for all cells within the area of interest. In addition, it is possible to specify the vertical extent.



Use the compass to specify which cells should be connected to the aquifer.

Aquifer modeling Numerical

Numerical aquifer - A set of cells in the simulation grid is used to represent the aquifer. Their position in the model is irrelevant.

The properties of the aquifer grid cells are set on the Cell settings tab. Hence the properties of an aquifer grid cell is independent of its actual position in the grid. E.g., when Number of cells is 2 - the aquifer is modeled using two grid cells. Numerical aquifers do not connect to local grid cells. Reservoir Engineering


You can select to use between one to five cells to model a numerical aquifer. To be able to include a numerical aquifer, Petrel needs the same number of grid cells that are undefined (for example, outside the grid) or have zero volume, porosity, or ACTNUM value. These cells cannot be part of a local grid set. The properties of the aquifer grid cells are set on the Cell settings tab, hence, the properties of the grid cells that are used to model the aquifer do not depend on the position those cells have in the 3D grid. If the numerical aquifer is modeled using one cell, it is the properties of this single cell that is used to represent the aquifer. All cells with a connection to the aquifer is consequently given boundary conditions depending on those properties. If more than one cell is used, all cells with connections to the aquifer are given boundary conditions using the properties of aquifer cell number one, while aquifer cell number one is attached to aquifer cell number two, and so on.



Fetkovich aquifers can effectively represent a wide range of aquifer types from the steady state infinite aquifer which provides constant pressure support to the “pot” aquifer, which is small compared to the reservoir and whose behavior is determined by the reservoir influx. The aquifer properties (compressibility, porosity, initial pressure, depth, productivity index etc.) are set on the Properties tab, and the aquifer connections to one or more faces of the reservoir are specified on the Connections tab.

The Carter Tracy aquifer model is a simplified approximation to time dependent model. The influence function of a Carter Tracy model is given as tables of dimensionless time versus a dimensionless pressure, hence, this aquifer model can be used to model changes in pressure with time. The default table models an infinite aquifer with constant terminal rate as given by van Everdingen and Hurst. To supply alternative tables, use Import (on selection) or Create new function and drop it into Properties tab of the Carter Tracy model. Reservoir Engineering


Make aquifer Properties tab

Required input depends on the selected aquifer model.

The different aquifer models require different input. Refer to the Online Help manual for details.

Exercises – Aquifers In this exercise, we will add an aquifer to see whether a better match can be achieved. Exercise Workflow • Use the Make/edit polygons process to draw a polygon that specifies the area that is influenced by the aquifer • Use the Make aquifer process to add an aquifer to the model Exercise Data In this exercise, continue to use the project from the previous exercise.



Add an aquifer Exercise steps 1. Open a 2D window and display one of the horizons along with the faults of your upscaled grid from the Models pane. 2. Activate the Make/edit polygons process from Utilities folder in the Processes pane. 3. Use the Start new set of polygons (deactivate old) tool . Draw a polygon which encloses the eastern part of the model. Use the Close selected polygon tool to close the polygon.

4. The new polygon is stored on the Input pane. Rename it to Aquifer boundary. 5. Make sure the Upscaled grid is active on the Models pane. 6. Go to the Processes pane, and open the Make aquifer process located under Simulation. 7. Select Create a new aquifer, and define aquifer model: Carter Tracy. 8. Rename Aquifer 1 to Carter Tracy. Reservoir Engineering


9. In the Connections tab, select the Aquifer boundary polygon on the Input pane, and drop it into the Area of interest field by clicking the blue arrow . 10. Select Grid edges as Drive direction. Make the compass connecting to the cell faces from all directions.

11. Under Vertical extent, select a Top limit of -2600 m (the oil-water contact). 12. Go to the Properties tab, and then select the fluid model Light oil + gas from the Input pane. Drop it into the process dialog using the blue arrow. 13. Type in a datum of -1600 m. 14. Click OK to save the aquifer model, leave the dialog open. 15. Display the grid in a 3D window now. 204 • Local grid refinements and Aquifers


16. Go to the Models pane, you will find newly created aquifer under the Upscaled grid > Aquifer folder. Toggle the new aquifer on. The cell faces connected to the aquifer are displayed in the 3D Window. 17. Now go back to the Make aquifer process, and deselect the directions between E and S in the compass (see picture below), then click Apply. Only the cell faces in the greyed parts of the compass are taken into account for the aquifer connection. This allows you to filter out the unwished aquifer cell connections.



Summary The Make aquifer process was used to model the presence of water at the edge of the reservoir. How to use The Make local grids process, which allows you to refine the simulation grid, was also demonstrated.



Module 7 - History development strategies Introduction In this module, you will learn how to set up a development strategy based on imported observed data. We will also look at how to import the historically observed production data. Prerequisites Basic knowledge of Petrel is required. Learning Objectives • Import observed data • View observed data in a function window • Make a history strategy • View line data • Optional: Use the History match analysis tool to view results


History development strategies • 207

Lesson 1 – History development strategies Development strategies describe to the simulator how a field will be developed – that is, which wells will produce or inject, at what rates and pressures they will flow in, what operations will be carried out on the wells over time, and so forth. Development strategies make it easy to keep track of how the control of a field evolves with time. For example, as new wells are drilled, the target field rates change, wells are converted from producer to injector, new platforms and manifolds are added and so on. Furthermore, development strategies make it easy to apply the same constraint to many wells by using well folders or different values of a particular constraint to individual wells.

The simulation is normally run in two phases: history match and prediction. By using the history match we try to match actual production history with the simulated history. We use geological, geophysical and petrophysical input to build a reservoir description, and from those, we build a simulation model. Next, we import actual production and pressure information, run the model, and compare the simulated results with the actual history. 208 • History development strategies


Sensitivity runs are used to identify which properties have the greatest effect on the simulation results. Tuning runs are used to modify the properties of the model to improve the match between simulated results and the actual production history.

This loop can be run many times.

When we have an acceptable match, we switch to prediction mode. This is where we use our calibrated model to predict the production response to new wells, new recovery techniques or changes to existing well operations. The focus of this lesson is History strategies.

History-Prediction History:

• Done to validate the model against history • Use observed rates as well control data • Use historic events; dates for perforations

Prediction:

• Used to predict future behavior • Give the rates or pressures that the wells should be operated at forward in time

The simulator needs the well paths (deviation surveys) in order to know where the wells are located in the simulation model. The well bore history is a record of the location and dates of perforations, squeezes, plugs, hydraulic fractures, etc. Normally, this information is put into an events file that is read into Petrel. The production history, or “vol file”, can be exported from OFM or Finder and imported into Petrel. Reservoir Engineering

The *.vol format is the format Petrel reads when loading historical production/ injection data. For simulation results or historical data, the export is on the Results pane. You can export simulated or historical data from an imported or existing simulation case as well as imported observed data in the *.vol format. History development strategies • 209

Import observed data Observed data are imported using the Well observed data format

Match the well name in the file to wells in your project

To import Observed data (historical data), right-click the Global observed data folder and select Import (on selection). Select the Well observed data file format. The imported data can be used in the Make development strategy process.

210 • History development strategies


Import observed data Go to the Data tab to match properties on file with a property identifier in Petrel

On the Data tab, you need to specify the type of data in each of the columns of the file you are importing. In the illustration, column three contains the bottom hole pressure (BHP).



Once the observed data vectors are imported, they can be viewed in a function window. To display observed data, you must select a vector (for example, oil rate), a well, and the observed dataset on the Results pane.

User interface

To make a history strategy, you can use the default strategies as a starting point and then add the features (rules) needed.



Use defaults

A history strategy Two rules are added: • Reporting frequency • History rate control

To create a history strategy using the Use presets button: 1. Make sure that you have loaded the necessary data into the project – wells, completion events and observed data. 2. Open the Make development strategy process. 3. In the dialog, click on the Use defaults button and select History strategy from the drop-down menu. The history strategy you just made contains: • The start and end dates from the first observed data in the project. These are shown in the strategy tree. • All the wells in the project. Do not worry if some of them did not produce or inject in the history – this will be detected on export to the simulator and the wells are ignored. The wells are all added to the default group. If you want group reporting, you will need to reorganize them. • The history rate control rule has been set up with the recommended defaults for history matching. If needed, change these in the Rules table. This refers to the first observed data set found in the project. If you have multiple observed data sets, and want to use a different one, simply drop the required set into the rule. Reservoir Engineering


• The report frequency rule has been set to monthly reports, as it is the most common choice; however, this can be changed.

History strategy Edit default rules

Drop in the observed data Edit control modes

Selecting Oil here, will make oil the target rate for the simulation

Edit time stepping



In between control changes, regular reports can be output from the simulator by changing the settings in the reporting frequency rule. By default, this is added to the first date of every strategy. However, it can be removed and can be copied to later dates if you want to change the settings, for example, to report yearly in the early part of a history match, and monthly in the most recent year.

Plot the observed data versus the development strategy in a function window.



Data averaging

Imported data is often densly sampled. The data is averaged within the report step in the Development strategy.

The imported data is averaged over the report step length selected in the Make development strategy process. Plot the observed data and the development strategy to see how the averaged data matches the observed data.

Define a history case Drop the strategy into the Strategies tab of the Define simulation case process dialog.



Go to the Strategies tab of the Define simulation case process to drop in a development strategy. Multiple strategies can be inserted by first adding a row to the table.

Exercises - Make a history development strategy Exercise Workflow • Import observed data • View the imported data • Make a history development strategy • View the development strategy data • Define a simulation case Exercise Data In this exercise, continue to use the project from the previous exercise.

Import observed data In this exercise, you will import observed production and injection data for the wells in the project. Exercise steps 1. Right-click the Global observed data folder under the Wells folder in the Input pane and select Import (on selection). 2. In the dialog that opens, select the file ImportData>Well_ Engineering>HistoryInj.vol then click Open. 3. In the Import observed data dialog that opens, make sure the well names in the file matches the correct well in your project. 4. Go to the Data tab. 5. Check that the Column number is correct for the data you are importing and that an appropriate Property identifier is selected.



6. After you have selected a Property identifier for all the vectors you are importing, make sure that you select Create new in the Global observed data column to add a subject to the Global observed data folder. 7. Click OK to import the observed water injection data. 8. Right-click the Global observed data folder under the Wells folder again and select Import (on selection). 9. In the dialog that opens, select the file ImportData>Well_ Engineering>HistoryProd.vol to import the production data then click Open. 10. In the Import observed data dialog that opens, select the Merge with radio button to make one observed data set containing both injection and production data. 11. Go to the Data tab. 12. Again, check that the Column numbers and the Property identifier are correct. 13. Observe that the bottom hole pressure is attached to the existing Global observed data subject. Click OK to import.



Exercise steps - Visualize the observed data 1. Open a function window. 2. Go to the Results pane, expand the Results folder and then the Dynamic results data folder. Expand the Source data type folder. Select the check box in front of Observed data. 3. Expand the Identifier folder and then the Wells folder to see all of the wells. Select to view well P04. 4. Select the check box in front of Oil production rate in the Rates folder along with Bottom hole pressure in the Pressures folder. Leave the Function window open.



Make a history development strategy In this exercise, you will create a history strategy using the Make development strategy process. You will see that the process automatically selects the imported observed dataset you imported. Exercise steps 1. Expand the Simulation folder in the Processes pane and open the Make development strategy process.

All dates are entered in the format YYYY-MM-DD, as recommended by the SPE standard.


2. Select Create new development strategy. 3. Click the Use presets button, and select History strategy from the drop-down menu. 4. Name the new strategy History. 5. On the Strategy tree, set the start date and the end date for simulation, 2005-02-01 and 2009-02-01, respectively. 6. Find the Rules folder in the Strategy tree (the left pane of the Make development strategy process dialog) and click the History rate control (Wells folder) rule. Note that the observed data set and the wells have been inserted automatically. 7. Make sure the Production control mode is set to Reservoir volume. For the Reporting frequency rule, leave the report frequency to the default every (1) month.


8. To save the history development strategy, click OK. 9. You will find the new Development strategies folder at the bottom of the Input pane.

View the development strategy data In this exercise, we will examine and compare the history development strategy to the observed data in a function window. Exercise steps 1. Return to the function window and make sure you have selected the following from the Results pane: well P04, Oil production rate, and the Observed data. 2. Add Development strategies in the Source data type folder to view in the window. You should now see your development strategy data and your observed data. Since they both are monthly, there should be no difference. 3. Reopen the Make development strategy process, and change the Reporting frequency rule to every three months and click OK. You can now see a difference between the averaged development strategy data and the observed data. Reservoir Engineering


Add a rule to limit the production pressures It is possible to add a rule to the history strategy to limit the allowed bottom hole pressures. Exercise steps 1. Open the Make development strategy process. 2. Select your History strategy in the Edit existing development strategy drop-down menu. 3. Click the Open ‘Add rules’ dialog button . 4. In the dialog that opens, left-click the History pressure limit rule, then click Add rule. 5. Use the arrow to drop the Wells Folder from the strategy tree (not from the Input pane) into the new rule. Enter a Minimum production BHP limit of 110 bar and a Maximum injection BHP limit of 380 bar.

6. Click OK to save the changes and to close the dialog. 222 • History development strategies


Define and run simulation cases In this exercise, we will define and run simulation cases using the history development strategy we just created. We start by running a case on the simple 3D grid that we initialized earlier. Exercise steps 1. Open the Define simulation case process and select to edit the Simple case. 2. Open the Strategies tab, and add a line to the table by clicking the Append item in the table button . Drop in the History development strategy that you just made by selecting it in the Input pane and clicking the blue arrow. 3. Click Apply to save the changes and then Run to run the case. We will now define and run a case based on the Upscaled 3D grid that we made in the upscaling exercises.

A message log will be shown while the simulation is running. Information on completion thresholds is printed on the message log. The completion threshold can be changed in the Settings for global completions. This will be covered in the chapter on completions.

Exercise steps 1. Open the Define simulation case process and select to create new case and give it name, Basic. 2. Change the grid from Simple to Upscaled. Make sure the Simulator is set to ECLIPSE 100.

3. Go to the Grid tab. Make sure you insert the properties you want to use for simulation. Expand Upscaled grid [U] under Models pane. Open the Properties folder and drop Permeability and Porosity into the Grid tab. To be able to use the blue arrow, you have to select the check box in front of it


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Five types of geometry files can be created for simulation: .OPF – most flexible, incl. curved faults, binary .GRID – incl. curved faults, binary .EGRID – straight line faults, binary .GRDECL – straight line faults, ASCII .GSG – incl. curved faults, binary

4. Go to the Advanced tab. Make sure GRDECL export format is selected on the Advanced grid sub-tab. (See tool tip for more information). Click Apply to save the changes. 5. You are now ready to run your simulation case. Click Run. Exercise steps In this exercise we will create a case, which include local grid refinements. 1. Open the Define simulation case process and select to create new case and give it name: NoAquifer.

2. Go to the Grid tab. Drop in the local grid set (Wells and Polygon) from the Models pane.

3. Click Apply to save the changes, and Run to run the case. 224 • History development strategies


Next, you will define a simulation case where an aquifer is used in addition to the local grid refinements. Exercise steps 1. Open the Define simulation case process. 2. Select the case NoAquifer that you made in the previous exercise from the drop-down menu. 3. Select Create new case, and name the new case Aquifer. Note that all settings from your case are preserved. 4. Go to the Grid tab. Add a row to the table . 5. Use the drop-down menu to select Aquifer. It is located at the bottom of the list.

6. Select the Aquifer (Carter Tracy) from the Models pane and drop it into the process dialog. 7. Click Apply to save the changes and Run to run the case. The next lesson will focus on viewing line data. Reservoir Engineering


Lesson 2 – Plotting data

Plotting data Open a New function window • Select line data and identifier from the Results pane • Select case from the Cases pane

To display simulation results in a Function window, you need to make a selection of Vectors (rates, ratios, pressure) and Identifiers (Field or some of the wells) from the Results pane, and afterwards, select one or more cases from the Cases pane. The Results pane contains results from volume calculations, simulations, and history matching runs.



Function window - settings Customize plot display

2

1. Go to the settings for Function 1 (of Function window 1) in the Windows pane or, double-click on a line. 2. Adjust settings under the Plot tab.

1

Line Styles – Color, Width and Type Petrel is set up to help you color the lines in an informative manner. You can select to colour the lines from the Settings panel of the function viewport. To access the settings, double-click on the line you are plotting in the function window or navigate to the settings of the function viewport in the Windows pane. The settings for the axis, the header, and legend are contained on the tabs of the dashboard as well as the Plot tab which displays the style settings for the lines plotted. Please, refer to the online help documentation for details.



Function window - settings Customize axis display

Adjust settings in the Axis tab to get the desired plot layout.

Navigate to the Axis sub-tab of the Settings dialog of the function viewport to change the appearance of the axis. Here, you can specify the size of the annotations, the number of ticks, and axis labels. Similarly, you can open the settings for the Header or the Legend and do your edits.



Results pane

Categorize results Right-click on Dynamic data and select Categorize results.

Use the Reset categorize to get back to the default configuration.

The Results pane can be organized in different ways. Right-click the Dynamic data folder and select Categorize results to change to another layout. Select the Categorize results option again. This will sort the data by phase.



Results pane Filter results

Right-click a vector, an identifier or a source type and select Filter results tree. Now, only data relevant to your selection is shown. Right-click the Dynamic data folder and select Cancel tree filter to cancel the filter.

The Results pane can contain a large number of vectors. If you only want to list vectors that contain data for a specific well or a particular simulation case you can right-click this subject and select Filter results tree.



Results pane

Export simulation results Select : • Result vectors • Identifiers • Case

Right-click the Dynamic data folder and select Export to export line vectors. In the Export dialog that opens, you must specify a file name and format. The only format available is Petrel Summary Data where the columns are separated by tabs. In the next dialog that opens, you can make a selection of result vectors, identifiers, and cases for export.



Plot window A plot window can be used to combine several view-ports.

A plot window is opened by selecting New plot window under Window on the menu bar. Use the New object in window tool to add new view-ports. You can combine several view-ports of the same type, or as in the illustration, you can combine different types.



Well section window

You can display a simulated property (such as oil saturation) through time for a selected well. If you hold your mouse over a well section, the value of that property will appear.

3D Viewing Summary data 1. Display relevant wells from the Input pane. 2. Go to settings for Dynamic data.

3. Select : Disc, Sphere, Stack or Bars0 4. Specify vectors to display from Dynamic results data. 5. Check the proper Identifier. Use the time player



The user can display summary data, for example Oil production rate in 3D and 2D windows. The summary vector can be displayed as a disc, stack, bar or sphere and the size represent the magnitude of the vector. The display can be animated through time.

Bubble maps

Time varying data

Display time varying data such as production rates as bubble maps • Insert new map window • Select result vectors from the Results pane • Select simulation case from Cases pane • Play time with the time player toolbar

Bubble plots can be displayed for observed data, development strategies, and simulation data. Use the time player at the bottom of the user interface to go to the time step of interest.



3D Viewing Streamlines

Streamlines are stored in the Streamlines folder at the bottom of the Models pane. In the settings panel of the streamlines, you can change the color and the thickness of the streamlines.

If FrontSim was selected as simulator, a Streamlines folder is added to the grid folder on the Models pane when the simulation is finished. Different attributes can be visualized on the streamlines, such as saturations, pressure, and travel times.



3D Viewing Streamline filters Use the Startwell or Endwell filters to view streamlines from/to particular wells.

The Startwell filter is useful for displaying all of the wells that are supported by an injector. Similarly, the Endwell filter is used to display all of the injectors that support one producer.

Exercise: Change the line style in function windows By default, simulated data is plotted with a solid line, development strategies are plotted with a solid line with points, and observed data is plotted as circles. The line color is selected automatically, however, you can override those defaults. Exercise steps 1. Continue to work with the function window that you used in the previous exercise. Or display any plot data from the Results pane. 2. Double-click on any of the lines in the plot to open the Settings panel for the line data. 3. To access the settings for one of the lines, select the line in the list at the left of the Settings panel by left-clicking it.



4. You can now edit the line and point styles by using the bottom right part of the settings panel. Select a line with of 8 pt, and click Apply to see the change.

5. Make sure that Auto line styles is selected, then select a different line color for one of your simulation cases. As you hit Apply, this color is assigned to that simulation case and will also be used in later plots. Reservoir Engineering


6. Deselect Auto line styles and then change the color of one of the simulation cases. Click Apply. The corresponding line changes color in the active function window, but the simulation case still has the same color on its settings panel. 7. Select the Axis tab of the Settings panel for the function window, then select the Annotation sub-tab.

8. Use the Annotation font drop-down menu to select another font size, and click the B button if you want to display the axis annotation in bold face. Click Apply to see the changes. 9. Select the Legend tab to customize the automatic legend. Select to use four rows in the legend. Click OK to apply the change and close the dialog.

Plot window It is possible to combine several view-ports in one plot window. Exercise steps 1. Open a New plot window. 2. Click the New object in window icon and select New function viewport. 3. Click and drag to insert the new function viewport. 4. Select one of your cases in the Cases pane. Select Oil and Water production rate from the Dynamic results data folder on the Results pane. Select Field in the Identifier folder. 5. Click the New object in window button again, but this time select New map viewport. 238 • History development strategies


6. Click and drag to insert a new map viewport. 7. Select the radio button in front of the Dynamic data subfolder of the Views folder on the Results pane. 8. Select to view Oil and Water production rate for all producers. 9. In addition, select to view a horizon from your upscaled grid on the Models pane. You should now see a bubble map of the production in the map window. Use the time player to go to the time steps of interest. 10. If you want to change the size of the bubbles, right-click the Dynamic data in the Views folder on the Results pane and select Settings. Use the sliders under in the Chart scale section of the Settings panel to set a new bubble radius.. 11. Go to a 3D window, and select to display water saturation at the last time step. Click the Copy bitmap icon. Then click the Paste bitmap button. The bitmap is stored on the Input pane. 12. Go back to your plot window and add the bitmap to view by selecting it from the Input pane. 13. You can drag the bitmap into another position and rescale it when you are in Select/pick mode


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Summary data in a 3D window - Optional You can visualize production data with multiple of other data types. The summary vector is displayed as disc, stack, bar, or sphere and the size represent the magnitude. Exercise steps 1. Open the 3D window, display the Producers from the Input pane. 2. Go to the settings of Dynamic data under the Views folder in the Results pane. 3. Select Chart type as Disc, click OK. 4. Under Dynamic results data, select Oil production rate and Water production rate. 5. Remember to activate the proper Identifier (select the check box in front of Producers under Identifier folder on the Results pane). 6. Use the time player to play production data in time.



View data on streamlines - Optional By rerunning one of your cases using the FrontSim simulator, you can view the results along streamlines. Exercise steps 1. Open the Define simulation case process, and select the Basic case from the Edit existing drop-down list. 2. Select Create new case, and name the new case Basic_FS. 3. Select FrontSim from the Simulator drop-down menu. 4. Click Apply to save, and Run to run the case. Then close the process dialog. 5. Open a 3D window and go to the Input pane, and select to view the Injectors and the Producers wells. Then, expand the Streamlines folder under the Upscaled grid in the Models pane and select to view your case Basic_FS. By default, the water saturation at the first time step is displayed. You can use the time player to view the saturation at later time steps. 6. Expand the Attributes folder and observe the other properties that can be viewed on streamlines. 7. Select only well I02 from the Startwell filter folder to only view streamlines starting in well I02.



Lesson 3 (Optional) – History match analysis



Match values are computed for all wells with observed data. In the expression on the slide: M is the match value that will be reported N is the number of points used to compute M, that is the number of time steps in the simulation or the number of observed data points. You select which of those to use in the History match analysis process dialog. S is the simulated value. S is a vector containing the simulated value for a specific well at each point in time. Hence, S is a vector of length N. O is the observed value, that is, O is a vector containing the observed value for a specific well at each point in time. O has length N. s is a normalization parameter that can be used to make sure all the match values are in the same order of magnitude.



Remember, that since the water cut is the ratio of water to liquid hydrocarbons produced in a well, it will always have values between zero and one. Therefore, a well with a large production is not distinguished from a well with a small production. Consequently, it is more reliable to use rates when computing the history match data.



History match analysis Select the Observed data set you wish to compare your simulation results to. Select settings: • the sample frequency • zero data filtering • normalization

The settings apply to all vectors by default. To change the settings for a vector: 1. Select the vector 2. Clear the Use default check box 3. Specify the settings



History match analysis Sampling

Sampling controls the times at which comparisons are made.

For infrequent observed data such as bottom hole pressure, use Observed frequency to compare only where observed data is available.

Remember, the expression for the match value M given in slide 4. The number N is determined by the sample frequency. If Observed frequency is chosen, the simulated data is compared to the observed data only when observed data is available. Consequently, N is the number of samples of the observed data. The simulated data will be sampled backwards. That is, at a time where there is observed data this value will be compared to the first simulated value backwards in time.



If Simulated frequency is selected, the simulated and the observed data will be compared at all simulation time steps. For each simulated time, the observed data are sampled forward in time, meaning that the observed data is treated as a constant from each measured point to the next. The average observed data value over one simulation time step is compared to the simulated value.



Zero data filtering should be turned on for the rates that were used to set the rules in the Development strategy process. If one of those rates is zero for a well, you would get a perfect match only because the well is closed for flow.

Note that the normalization parameter s can be used to give one vector, or a selection of the vectors, more weight than the others in a combined match. That is, if a large normalization parameter is used for some of the vectors, the match value for those vectors will be relatively small compared to vectors that were assigned a small parameter. If you select to use Absolute normalization, you must select the size of the normalization parameter carefully.



History match analysis Results viewing

The history match set is stored in the Results pane You can use the data to: • Compare wells and vectors for a case • Compare wells and vectors between cases

There are several options to view match data: Function window. Crossplots of two vectors or a vector and a well can be displayed in a function window. Also a vector or combination of vectors can be plotted for several different cases. Map window. In a map window, the match values can be plotted at the well position. The data can be viewed together with a surface or a horizon. Either two cases can be compared at each well, or the match value for the different wells can be displayed for a single case.



In a map window, you can select to view data in either a qualitative or in a quantitative mode. Qualitative mode: The results are grouped into five bins, ranging from poor to perfect match. Quantitative mode: The actual match values, M, are displayed. When viewing match values in the quantitative mode, be aware that the maximum value depends on the normalization parameter you have selected. Also, the maximum value may have great variations between the different vectors.



In the settings panel for the History match set, you can set the Threshold limits and the Equality number. Updating these values does not require re-sampling of the data, it only changes the appearance of the plots. Threshold: The settings are used to visualize match results in the qualitative mode. All vectors with a match value lower than Min will be reported as Match. All vectors with a match value greater than Max will be reported as Poor. Note that the size of the parameters Min and Max must be chosen depending on how you select to normalize the match. Equality+/-:The number you enter here is used to visualize the difference between two cases. Vectors with a match value less than this number will be displayed as being equal.



Match values in Map window Single case

A bubble map shows the match statistic for one or more vectors at each well. Here, the well P04 has the worst oil production match.

In the above illustration, the match values are displayed in a quantitative mode, which means the actual match values are displayed. If a qualitative mode was selected, the results would be lumped into five categories from Match to Poor.



Match values in Map window Case compare

Switch on Case compare mode Select vectors and wells in the Results pane. Select two cases to compare in the Cases pane.

In the above illustration, two cases are compared. The values are lumped into three categories: Case 1 is displayed as better, equal, or worse than Case 2.

Function window

History match statistics settings You can select the color for: • The best match • The worst match • The remaining match values You can select to view: • A combined match value for all vectors • A separate match value for each vector



If you compare several cases in a function window, you can select to assign the best and the worst match-value a specific color. If you select to view the match for several vectors simultaneously, you have two choices. You can either view one combined match value for all the vectors for each case, or you can view a separate match value for each vector for each case.

Function window Cross plot two vectors

Cross plots can highlight if improving one match makes another better or worse.

To make a crossplot: 1. Use the right mouse to select which vector to plot on the x-axis. Then select a second vector for the y-axis. 2. Select the cases you want to compare in the Cases pane. A trend to the origin indicates both matches improve together, while a trend to the ends of the axes indicates improving one match worsens the other. You can crossplot two wells in a similar way.



Function window

Single vector versus case number

In the illustration, you can see the match values for a single vector, water production rate, for all wells in several cases. In this example, the user has selected to give the best match the color green and the worst match the color red. The remaining matches are in black.



Exercises – History match analysis In this exercise, you will run the History match analysis process on the history cases we set up previously. The resulting match-vectors will be used to explore whether the simulated results reproduce the observed production data. Exercise Workflow • Run the History match analysis process • View results in function and map windows for a single case • Adjust settings to improve the visualization Exercise Data In the following exercise, we will continue with the project we made in the previous exercises.

Run history match analysis Exercise steps 1. Open the History match analysis process from the Simulation folder on the Processes pane.

2. Select to Create new match. Make sure that your historical data set is selected as the observed data set. 3. Select Water cut, deselect Use default and select Absolute Normalization. Enter 1 as the normalization parameter. 4. Select the Bottom hole pressure, and deselect Use default. Then, select Observed frequency. 5. Click OK to compute the math vectors. 256 • History development strategies


View match data in a map window Exercise steps 1. Open a New map window. 2. Select your Aquifer case in the Cases pane. 3. Select to view the Base horizon by selecting the check box in front of it under your Upscaled grid on the Models pane. 4. For only viewing the contour lines, right-click in the Horizons folder under the Upscaled grid and select Settings. 5. Go to the Solid tab and deselect Show. Click OK to close the settings. 6. Go to the Results pane and select the new match set. Also select Bottom hole pressure from the Vector matches folder. Select all the producers in the Identifier folder.

7. If you do not see the wells, click the View all in viewport button . 8. Open the settings for History match statistics by rightclicking the folder and then selecting Settings. 9. Go to the Map window tab and select the radio button Quantitative. 10. Still on the Map window tab, select the check box Enable bubble plots. Click Apply. 11. Go to the General tab and click to change the range of the color legend. In the dialog that opens, click Max and Min to get the range of your pressure match vector. Click Reservoir Engineering


Apply. Notice how well P01 has the poorest match in bottom hole pressure.

12. Turn off the Bottom hole pressure, and select to view the Oil production rate instead. 13. Switch to Qualitative mode in the Map tab of the Settings panel for the History match statistics, then click Apply. 14. Open the settings for your New match set and enter the threshold for the match values that should be considered good and bad. Select Min =0.1 and Max=3. You should now see a qualitative match of the oil production rates. Notice that well P04 has a poor match in oil production rate.



View match data in a function window Exercise steps 1. Open a function window. 2. Select all of your cases on the Cases pane. 3. Open the settings dialog for the History match statistics folder and go to the Function window tab. 4. Select the check boxes Color best match and Color worst match, then check the box Combine. Click OK to close the dialog.



5. Select your New match set, Bottom hole pressure, Oil production rate and well P04 from the History match statistics folder on the Results pane. 6. You should now see the match values in the function window.

Compare cases in a Map window Exercise steps 1. Open a Map window. 2. Select to view all wells and the Bottom hole pressure from the History match statistics folder on the Results pane. 3. Activate the Case compare button in the function bar. It should now have an orange background color. 4. Then, select to view both the Aquifer case and the Simple case. 5. Right-click the New match set folder on the Results pane and select Settings. 6. On the settings panel, select the Bottom hole pressure, then set Equality to 0.3.



7. You should now see that the Aquifer case has the best match for most of the wells.

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Summary In this module, you learned how to use the Make development strategy process to set up a simulation case using observed well data as input. You also learned how to import observed data. Finally, it was demonstrated how to use the History match analysis process to compare simulated results to observed data.



Module 8 - Well Engineering Introduction In this module, we will import well data, digitize a new well in Petrel using the Well path design process, and complete the well with completions using the Well completion design process. We will use various Petrel windows and tools to create, quality check and inspect the well data. Prerequisites Basic knowledge of Petrel is required. Learning Objectives In this module, you will learn: • How to import well data into your Petrel project • How to design a well path using the Well path design and the Laterals design processes • How to use the well completion design process to insert completions for your wells • How to QC wells trajectories and completions.


Well Engineering • 263

Lesson 1 – Import and Design Well Paths

When you import a well header, make sure to select the correct file format. In the import dialog that appears, notice that there is a capture of the file you are importing at the bottom. View the data in the file capture, and fill in the column number for the x and y coordinate and the depth data into the Columns part of the dialog. To import well header data: • Right-click the Wells folder and select Import(on selection) from the drop-down menu • Select Well heads (ASCII)(*.*) as the file format

264 • Well Engineering


Import well paths Use the Well path/deviation(ASCII) format to import the well trajectory. Match file name to existing well name.

Import well path / deviation file If the well is not vertical, it is necessary to import the corresponding deviation file. The deviation file will be attached to the well header already imported. Select a well path input file by right-clicking on the Wells folder and selecting Import (on selection). In the window that opens up, select the files defining the well paths for one, some, or all of the wells and select the appropriate format (for example, Well paths/deviations (ASCII)(*.*)). Associate each well path with a well The illustration above shows the window that will open up while importing. The window displays the well names in the file in the left column. Use the right column to match the deviation data on file to the correct well in your project Link the field types with the file’s columns As for the well heads file, an Import well deviation window will open up where you will have to specify which column in the file corresponds to each of the attributes, such as MD, Inclination and Azimuth; X, Y and TVD. Reservoir Engineering

A well created by Create well (vertical well) or imported into Petrel using well deviation format is created by the minimum curvature interpolation method. This method is very different from the advanced drilling trajectory algorithm available in Well path design, both in objective and mathematics. Well Engineering • 265

To import branching wells, you need to use the Multiple well paths/ deviations file format. Notice that if Well B is branching off from Well A, then it needs to be named Well A%Well B on the file you are importing.



Well path design We will now focus on how to make new well traces in Petrel. The simplest way to add a new well, is to make a new vertical well. The Well path design process which is located in the Well engineering folder in the Processes pane allows you to digitize new well traces, and the Laterals design process makes it easy to add laterals to an existing well.

Well path design Make vertical wells Digitize well paths Make wells using the Well path design process



Simple vertical well

A well created by the Create well is created in the DxDyTVD domain, and is not intended to be modified by the Well path design process. Therefore these are the only editable values on the spreadsheet.


To insert a new vertical well into the project: 1. Decide where in your 3D model you want to locate the new well. 2. Click the location in a window using the Select/pick mode. The status bar will display the X and Y surface coordinates. 3. Right-click the Wells folder in the Input pane and choose New well from the drop-down menu. 4. In the Create new well dialog, enter a name for the well, select a well symbol and enter the X and Y coordinates. You can also enter a top measured depth and a bottom measured depth to specify the depth interval of the well.


Well path design Trajectory

A well path is generated between the design points. The path is a combination of straight and curved sections; an approximation of how wells are drilled in the real world.

Petrel algorithm - Advanced Design Trajectory - will attempt to restrict curvature to a specified dog leg severity (DLS).

The well path design process Well path design lets you create paths for wells either manually by point-and-click, or automatically using the Create best fit well and Well optimizer methods. When designing a well manually, the first step is to start digitizing the well path and edit the well points into position. This can be done in several ways, and will be described on the following pages. Petrel makes well traces through the design point which is a combination of straight lines and curved sections. Petrel will use a ‘J’ curve between points 1 and 2 (straight section then curve), a straight section between points 2 and 3 and ‘r’ curves between subsequent points (curve then straight section).

You may want to change vertical exaggeration to 2 instead of the default of 5. This should give a better understanding of the well geometry

The DLS settings play an important role in generating the well path using the ADT algorithm. If you are not happy with the generated well path then he can change these settings, or edit the well interactively.

The Well path design process is creating wells according to the drilling constraints. Therefore, there is additional data associated with the well traces exposed in the spreadsheet for each well. The well is created in the XYZ domain (design points). Consequently, these are the only values that can be edited in the spreadsheet. Reservoir Engineering


Dog leg severity (DLS)

The algorithm will attempt to design a well that passes through all of the design points with a curvature which is smaller than the “requested upper” dog leg severity (DLS) set by the user. This is done by using a series of straight sections and curves of the requested DLS.



Dog leg severity (DLS) DLS is the deviation from a straight path in degrees per 30m (100 ft).

The illustration shows the result of using different DLS constraints on the well path. In the picture at the top, a maximum DLS of 5 was allowed, while in the bottom picture the highest DLS is set equal to the requested DLS of 3. The method for computing a trace between the design points, needs input to decide to what degree the path is allowed to deviate from a straight line. You need to specify the Dog leg severity (DLS) of the resulting well trace. The DLS is the deviation from a straight line measured in degrees per 30 m (or 100 ft ). Requested - this is the dog leg severity which will be used on the curved sections of the well path if possible. Maximum - the maximum dog leg severity which can be used in the well path. If the requested DLS can not be achieved because of the positioning of the design points (the points are too close together and at a too severe angle), then the algorithm will use the highest DLS required without exceeding its maximum. Reservoir Engineering


Digitize well path A) Digitize on a General Intersection Display all the data of interest: • Property • Horizons • Faults • Seismic etc. B) Digitize on a filtered property

Well design walkthrough A new well path is digitized in the Well path design process by using the Add new points button. Later, the digitized points can be edited and deleted, and additional points can be added.

It is also possible to first create a polygon (that can consist of several straight line segments joined together), create a vertical section along the polygon, display data on the section and then digitize.


There are several ways of digitizing the well path, depending on the available data. Digitize on a General intersection (GI) - You can create a GI and position it in the place where you want to digitize the new path. Any type of data can be displayed on the intersection. It is possible to perform detailed editing at any time, for instance, if you do not want your well along a straight line. Digitize on a filtered property - Use the value filter in the property filter to filter on, for example, high porosity values, and use the zone filter to view the different zone(s) you want. Digitize in 3D view and attach the digitized points to the cells that are left after filtering. Reservoir Engineering

Create a STOIIP map from volume calculation - This map shows the density for each cell. The STOIIP map can be draped across the surface representing the top reservoir. The surface used to digitize the new well should be placed below the top of the reservoir to make sure that the well trace is always inside the reservoir.

Digitize well path 1. Activate the Well path design process 2. Continue digitizing on an existing (active; bold) well…

3

Tip: Use these two options to increase or decrease point size.

3. ... or Start new well (Deactivate the old) 4. The new well trajectory is stored in the Proposed wells folder under the main Wells folder.

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4


Well type

Simple

Side track

Stand alone

You have the possibility to extend the proposed well trajectory to the surface by selecting one of the Advanced algorithm options: Simple : The well head is assumed to be vertical above the uppermost design point. Standalone : The well head, KB and MD need to be provided by the user. Side track : User must specify the main well to which Petrel will connect proposed trajectory. The Simulation trajectory algorithm is available only for imported wells from simulation deck. The algorithm joins the design points with straight lines.



Edit well path 1. Activate the Select/pick mode from function bar 2. Pick a node (yellow) and move by depressing the left mouse button 3. Depending on the Move options in function bar (A), you can move along the Line tangent (B) only, in Vertical plane (C) only or Free movement

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3C

3B

3A

2

Edit well path 1. Move tangent – select cylinder part of widget (turns yellow) and move up or down. Pressing CTRL shifts direction 2. Active the Z-value selector icon and enter a depth for the node (press =); moves along tangent vertically

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3. Move vector arrow (turns yellow). This will not move the node but changes the curvature (A) 1


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3A


Exercises – Import well data and design well paths In this exercise, we will import a deviation file which contains a multi-lateral well. We will also make a vertical well and digitize a horizontal well trajectory. We will use the Reference project tool to transfer a well between projects. Exercise Workflow • Import well deviation • Make vertical well • Make a horizontal/deviated well and edit the proposed trajectory • Reference project tool. Exercise Data In this exercise, you will continue on the project you have been working on in the previous modules and exercises. If you do not have X, Y data (well head X-coordinate, well head Y-coordinate) in your deviation file (.dev), you must first import well header (file of type: Well heads (*.*))

You can also import directly into sub folders instead of having to move the well after import.

Import well data Exercise steps - Import the well path deviation 1. Right-click the Wells folder and select Import (on selection) from the drop-down menu. Use the file of type: Multiple well paths/deviations(*.*). 2. Select the file ImportData > Well_Engineering > ImportWells.dev and click Open. 3. In the Import multiple well paths dialog that opens, select X,Y,TVD as Column input data.

4. Look at the file capture at the bottom of the import dialog and enter the correct column number for X, Y, and TVD. 276 • Well Engineering


5. Under Other settings, select the button Name as part of header. 6. In the Name prefix field, enter the characters that precede the well name in the file you are importing.

7. In the Data format field, enter a N for all columns containing a number and an S for all columns containing a text string.

8. Click OK to do the import. 9. Add a new sub-folder to the Wells folder and name it Imported. 10. Move the imported wells P07 and P07%P08 into the Imported folder that you just added. 11. Select to display the new well in a 3D window.



Make a vertical well Exercise steps 1. Right-click the Wells folder and select New well. In the dialog that opens, give the new well the name P09, and place it at (x,y)=(4500, 11500) m. 2. Select an appropriate well symbol. 3. Select the check box Specify vertical trace, then enter a bottom MD of 2900 m. 4. Click OK to make the well. 5. Drag and drop the new well into the Producers folder.

. 278 • Well Engineering


Setting up the 3D window This exercise will walk you through how to display relevant data when digitizing wells, such as oil saturation at the end of history. Also, it is useful to display the other wells and the faults so you can see the proximity and avoid hitting them when designing the well. Exercise steps 1. Open a 3D window. 2. Go to the Cases pane and select the Aquifer case. 3. On the Results pane, expand the Dynamic folder under Simulation grid results, and select to visualize Oil saturation (SOIL). 4. Display the last time step 2009-02-01, using time player at the bottom. 5. Right-click the Oil saturation (SOIL) property and select Create 1D filter. 6. Select to filter out all values below 50% of oil saturation. Click Apply.


Be aware of vertical exaggeration, which by default is set to 5. You may want to change Z-scale to 2 from Petrel Tool bar.


7. Expand the Filter folder on the Input pane. Then, expand the User sub-folder in which your new filter is stored. Select the check box in front of it to turn it on or off. 8. Next, click once on the Define simulation case in the Simulation folder in the Processes pane making it the active process. This enables the property function toolbar to the right of the 3D window which we will use.

If you do not have any properties to move along, you may also use a surface or horizon. Shift the surface up and down a short interval using the Operation tab in the settings for the surface. Then you can digitize on that surface to trace the well.

9. Use the Display the cells with same K button and the property player buttons to move through the grid in K layers. In this way, when you digitize on the grid, you can move through the reservoir. You can also use the I- and J-direction filters 10. Turn on all existing wells from the Input pane, to avoid collisions. This is one way out of many to set up the 3D window ready for digitizing new well trajectories. Exercise steps 1. Alternatively, you can use a General intersection as a target when digitizing the well trajectory in combination with the saturation property. 2. Go to the Input pane and turn off the User filter for saturation you have made in the previous exercise Oil saturation (SOIL) 1 - Aquifer. Deselect filtering along K-direction as well. 3. Insert a new General intersection by right-clicking the Intersection folder located in the Models pane under Upscaled grid. Next, select Insert general intersection 4. Use the Manipulate plane button and the general intersection player toolbar to move the general intersection into the location you want to digitize the well.



5. When the general intersection is in the position you want, turn off the Oil saturation (SOIL) property from Simulation grid results in the Results pane. 6. Toggle on Visualization on plane and then select to display a property on the plane, for example, Oil saturation (SOIL) property. The property will now be displayed only on the intersection.

Open the settings for the General intersection plane and set the transparency very high (90%). Also, from the function toolbar, select to Make the point size bigger so that the well points are more easily seen.

From the General intersection player toolbar, use either the Clip in front of plane or the Clip behind plane buttons to filter out the cells that covers the plane.



Well path design Best practice: Now that the 3D window has been set up to start digitizing a well path, be cautious. Start off simple and only add more complexity if it is necessary. Using the digitizer and the widget functionality in Petrel is tempting, but you can easily compromise a well with a well point that is off. Exercise steps 1. Activate the Well path design process found in the Well engineering folder on the Processes pane by clicking it once. This enables the well path design function toolbar that we will be using. 2. Use the Add new points button in the well path design function toolbar and start to digitize (click) on the general intersection plane.



3. To move a well point interactively in the 3D window, use the Select/pick mode and click on the well point. The well point turns into a widget that can be moved around. Petrel will observe the dog leg severity constraints at all times and give you a warning if it is exceeded.

The new well will automatically be named Proposed 1 and will be saved in a new Proposed wells folder under the Wells folder in the Input pane. Right-click on the well and open its settings. Now, you can define if the well should be a simple well, a standalone well, or a side track well that tie into one of the existing wells in the project. 4. For our project, we will state that the well is a standalone. We need to specify a well header location and a kick-off measured depth. Enter some reasonable values that will not break the dog leg severity for the well.

It is often easier to delete a well point, or the entire well, and start the well design again, than to spend time adjusting and fixing.

To resize, select or move the well design points you will have to either turn off the general intersection plane or move the plane slightly. Reservoir Engineering


5. Remember to change the well symbol for the well, and to rename the well into something in accordance with the other wells (P10). The well will be stored in the Proposed wells folder.



Reference project tool This exercise will show you how to use the Reference project tool, which is useful when sharing data with others. Exercise steps 1. Go to the File menu and select the Reference project tool.

. 2. Click the Open project button in the Background project part of the dialog that opens.

3. In the file browser that opens, select the RE_ Reference_2010.pet file, then click Open. 4. Expand the Wells folder for this project and select the check box in front of the P08 well.

5. Click the left arrow to copy the well into your project. 6. Close the Reference project tool, and save your project. 7. Display the well you just copied. Reservoir Engineering


Lesson 2(Optional) – Automatic well placement This lesson shows an automatic way of creating wells using the Well path design process :

Best fit method 1. Open Well path design. 2. Select method.

This method will place the well in the geological body defined by the user.

Create best fit well The Best fit well method will place a well in the discrete 3D property defined by the user. The well spacing, length, and orientation are controlled by the property that is used as input.



Best fit method 1. Define the target area for the new well. 2. Drop it into the process. 3. Give the new well a name. 3. Select wellhead or attach to an existing well. In the process settings, you can turn on the active filter to be applied together with the target body.

Best fit method

Advanced well placement considerations

Shifting offset a) Multilaterals b) Limiting surfaces as constrain c) Collision detection Reservoir Engineering

Click Make run before you close the dialog.


The algorithm will place a well through the target body, honoring the constraint given by the user. The topology of the selected target area (body) can lead to multilateral solution. On the process dialog, you can allow for laterals and also limit their lengths. You can select to constrain the well(s) target points between an upper and a lower surface. Notice that you cannot use a horizon from the 3D grid, only surfaces from the Input pane are accepted as input. If the same surface is inserted for both Upper and Lower, Petrel will shift the well target points to that surface. Alternatively, you can enter the maximum and the minimum depth where you want the well path to be placed in between. It is possible to shift the wells in the X and Y direction relative to the input target by entering the desired offset. Notice that by doing so, the resulting wells may not hit the input target. If a collision is detected, a warning message will be logged.

If you turn on Collision detection , you have to specify a well or a group of wells that the new well should avoid.

Laterals design Laterals design



The process allows you to create complex multilateral trajectories based on existing well(s). There are two types of laterals: Fishbone and Fork laterals.

Laterals design

You need to supply the depth (reference MD) that the first new lateral should branch off from the mother bore. Either drop in a surface, in which case the reference MD is calculated as the intersection of the main well with that surface. Or else, enter the depth (in TVD).



Laterals design

On the Laterals template tab, you can select the laterals type : Fork or Fishbone. There are several settings for both templates: Offset MD – This value will define the starting point MD of the first lateral and is an offset to the reference MD provided on the general tab. Spacing – specify the distance (MD) between the starting points of two consecutive laterals. Relative azimuth – is the angle between the first target point of the lateral and the starting point of the main well. In cases where there are more then one lateral, the first will use the relative azimuth, the second will use the opposite of the relative azimuth and so on. Use the Advanced settings if you want to use different settings for different laterals to the same main well.



Laterals design

You can constrain the well target points (computed by algorithm) between two surfaces. If the same is used for upper and lower Petrel will place well target points directly onto that surface.

Exercises – Automatic well placement - optional Exercise Workflow • Convert simulation results to grid property • Use grid calculator to define a discrete property • Well path design - Create best fit well • Laterals design In this exercise, we will place a well in the target geobody. Exercise steps - Make a well target 1. Display the Oil saturation (SOIL) property from the Results pane. Use the Aquifer case from Cases pane. Set the time player to display the last report step. 2. Expand the Grid filter under Simulation grid results in the Results pane and deselect all segments except Segment 4. Reservoir Engineering


3. The part of the reservoir that has high oil saturation and only one producer is now displayed. 4. Right-click Oil saturation (SOIL) and select Convert simulation results to grid properties. Click OK in the dialog that opens up. 5. Go to the Models pane. Under the Upscaled grid you will find the AQUIFER folder (name of the case/ run from which the property originated). 6. Expand the AQUIFER folder and find the SOIL[0] [Feb 01.2009] property. Right-click and select Calculator. 7. In the Calculator window, select to Use filter. The filter that is applied is the same as the ones applied in the active 3D window, hence, in this case, we will only compute a property for Segment 4. 8. Use the Attach new to template drop-down menu to select the General discrete template. 9. Enter P11_target=, then left-click the SOIL property in the Select property variable pane to obtain the expression as shown in the illustration below.



10. Click ENTER in the calculator dialog. 11. The new property is stored in the Properties folder of the upscaled grid. Display it in the 3D window. Exercise steps - Create best fit wells 1. Open the Well path design process from the Processes pane. 2. Select method the Create best fit well. 3. Drop the new P11_target property into the process window using the blue arrow. 4. To specify the well head location, there is a pre-made Wellhead P11 point set stored in the Input pane. Drop it in to the process dialog. 5. Change the maximum length of the new well to bee 4000 m. 6. Leave the other settings default.



7. Click Make run. Find the new Optimized wells folder in the Input pane and visualize the new wells in your 3D window.

The reference MD is the MD value of the input well that corresponds to the TVD given as input to the process. You can left-click the main well in a 3D window at which point where you want the first lateral to branch off. The depth value is then reported in the status bar.


Exercise steps – Laterals design In this exercise, we will make a multilateral well using the Laterals design process. We will use the horizontal well we digitized in the 3D window as the input main well. We will add laterals using the Fork type. . Exercise steps 1. Display well P10 from the Input pane. 2. Open the Laterals design process from the Processes pane. 3. On the General, tab drop in well P10 as a main well. As Reference MD, enter a positive number. This is the point (in total vertical depth) where the first lateral branches off P10. Leave the DLS settings default. 4. On the Laterals template tab, select Laterals type: Fork. Set the Number of laterals to 2 and enter Laterals length : 3000 m.


5. Click OK. The new Laterals folder is added to the Wells folder in the Input pane. Display the new laterals together with P10. 

You can adjust different parameters including DLS to obtain a suitable laterals.

Lesson 3 – Results, reports and quality checking



Well manager Well manager is a tool that displays and allows to edit well data in a spreadsheet

Well attributes: • Default attributes • User attributes • Check shots • Well log • Well completions

The Well manager gives you an overview of all wells in your project. It allows you to sort and filter on well names.



The well paths can be viewed and edited in a spreadsheet. To access the spreadsheet, right-click the well and select Spreadsheet from the drop-down menu.



Intersection with Horizons Report

From the Settings dialog of a well, you can select to create a well report that can be handed over to the driller. You can either create a report that tells you all the exits and entries of every zone, or you could enter the spreadsheet for the well and get a listing of the well points, with different types of attributes.



Intersection with Horizons Make well tops

Also on the Settings dialog for the wells, you can select to add synthetic well tops to the active well tops folder at the positions where your new wells intersects the horizons of your 3D grid. Those can be useful later when placing completion items.



There are many options in Petrel to quality check and report the resulting well path. Both the dog leg severity and the error propagation cone can be displayed along the well path. It is also possible to make synthetic logs from grid properties and to view properties on a vertical well section along the well path. The designed wells can be reviewed and edited in a spreadsheet.



Display the Dog leg severity

Click the button

to display the DLS.

Synthetic logs 1. Open the Make logs tab in the settings for the new well and select a property. Click the Make logs button. 2. Click the Make logs button. 3. Open the Style settings for the property from the Global well log, and select the Draw log as 3D pipe option.

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Synthetic log curves - can be created from the properties in the active 3D grid or from the zones in the 3D grid. Synthetic logs can be displayed in 2D or in 3D as a cylinder along the well path where the thickness of the cylinder represents the value of the log. To quality check a new well, you can create a vertical well intersection and display different types of data on it. Also, it is possible to create synthetic logs along the well path, based on input from the 3D grid. This could be synthetic property logs (Phi, Perm, Sw, etc) or zone logs. The synthetic logs can be displayed in the well section window like any other type of log. Vertical well intersection – right-click on the new well to insert a vertical well intersection. The blue button allows you to display data on the intersection. The data available for display will show a blue check box. Examples are seismic, properties, horizons, faults, and polygons.

Vertical well intersection 1. Right-click the well and select Create vertical well intersection. 2. Use the “blue” button (A) to display on the plane (B)

2B 1


2A


Exercises – Results, reports and quality checking In this exercise, we will quality check and report resulting well trajectories. Exercise Workflow • Well manager • Well tops and well report

Well manager and saved searches The Well manager gives an overview of all wells with their attributes, well logs and completion items. It also allows you to edit and change the well data.

You can view the completion items in the 3D window. Click in the Global completions folder in the Input pane to view the completions for the wells.

Exercise steps 1. Right-click on the Wells folder in the Input pane and select Well manager from the drop-down menu. The well manager window opens.



Do not delete any wells from your project, there is no undo! For some functions, you need to select a well first (click on the row number in front of the well names)

Saved searches let you display and access wells based on specific search criteria. This helps organizing well data into place holders without the need for duplication. Several types of search criteria can be applied. Each search can be used in isolation or in combination with other searches.

2. Hover the mouse pointer over the icons at the top toolbar to get a tool tip for what functionality they provide. Try a few of them. Warning: . 3. Click on the Show button to get a drop-down menu with attributes that you can view. Deselect the default attributes and select to show Well completions. 4. Next to the Show button is a Filter button . This filters the Well manager based on any saved searches defined in your project. See the tip for more information. 5. Show the default attributes again in the well manager, and click on the Edit points button at the bottom of the well manager window. Select to edit the total depth TD (MD), and notice that the column now has a white background and the values can now be edited.

Well tops and well report Petrel has all the information required to make a detailed well report and well tops for our new well. Exercise steps 1. Drag-and-drop well P08 into the Imported folder. 2. Open the settings for the well P08 and go to the Report tab 3. Select the options Make well report and Iconize points as Horizon in active well tops. 4. Make sure the upscaled grid is active, then click the Insert active 3D grid (in Petrel explorer) button. 5. Click the Run button to generate the report and to make well tops where the new well penetrates one of the horizons in the grid.



6. A well report will open in a spreadsheet, and well tops have been added to the Well tops folder on the Input pane. We will use this information when we insert completion items.



Lesson 5 – Well completion design

Well completion design

The Well completion design process allows you to create or edit well completion objects for the wells in your project. All completions have their own settings panel that contain the physical properties of the completion and the date at which the completion is introduced to Petrel. Most of the completion components can be utilized with both ECLIPSE and FrontSim for simulation. • Casing - The well is closed for the depth interval of the casing. • Liner - The well is closed for the depth interval of the liner. • Perforation - The well is open to flow for the depth interval of the perforation. • Squeeze - The well is closed to flow. • Stimulation - The transmissibility factor for the connection between the well bore and the cells it penetrates is altered according to the skin value the user selects. 306 • Well Engineering


• Plug - The well is closed at the position of the plug and downwards. • Well test - The well test completion items can all be used with the standard well model. • Hydraulic fracture-The well connection factor is altered based on the settings of the hydraulic fracture.

Define well segmentation

There are two ways of computing the inflow to wells with ECLIPSE; namely the standard and multi-segment well model. The multisegment well model is a special extension to ECLIPSE. The following items are exported to ECLIPSE only if they are used with multi-segmented wells settings - Inflow control devices (ICDs), Flow control valves (FCVs), Gas lift valve, Gauges, and Pumps. The Heater can only be used with ECLIPSE 300. The standard well models treat the entire well bore as a single entity, with constant or averaged fluid properties throughout the well. Such models neglect pressure drops due to friction and inter-phase slip. This Reservoir Engineering


is a reasonable approximation for vertical wells producing from only one zone. However, in a horizontal well, friction is very important. When you have one zone producing gas and another producing oil, the difference in fluid properties (density and viscosity) is important.

VFP (vertical flow performance) tables give the BHP as a function of the flow rate, the THP, the water and gas fractions. VFP tables cannot be made in Petrel, but they can be imported into the Input pane and used in the Define well segmentation process.

The multi-segmented well model in Petrel and ECLIPSE divides the entire well bore into segments, similar to how a reservoir is divided into cells when making the grid. Petrel gives each well segment the physical properties of the casing or tubing that it contains, allowing ECLIPSE to accurately model the fluid physics throughout the well bore. The Petrel Define well segmentation process allows you control of the length of the segments, what angles they cross, and how the perforated zones connect to them. Multi-segmented wells is not within the scope of this class.

FrontSim does not support the segregated or multi-segmented well models. Multi-lateral or horizontal wells, or wells with large amounts of cross flow, are likely to give different results from FrontSim than from ECLIPSE 100 or ECLIPSE 300. FrontSim does have a simpler well bore friction model for use with horizontal wells, but Petrel does not generate data for this option.



Completion items Input pane

Completions appear on the Input pane in a folder for each well Edit completion data: • in the Well section window • from the Completions manager • on the Settings panel • using the Operations tab on the process dialog

Insert a completion item

Click the Add/edit a perforation icon from the function bar. Left-click in the Completions track panel to insert a new perforation.

Enter a date for the perforation.



To insert a new completion item, select one of the icons in the Function bar (Perforation, Casing, Liner...), and left-click in the Completions track of the well section window. You are prompted with a dialog in which you need to specify the start date for the new item. Once you have entered a date and closed the dialog box, the new item is added.

The completion items can be edited in the well section window. To do so, hover the mouse pointer over a completion item. • When the pointer looks like a hand, you can drag the item up or down • When the pointer looks like a double arrow you can stretch or squeeze the item You can also zoom and squeeze the well section display. To do so, hover the cursor above the depth panel. When the cursor looks like a hand, you can pane the view. When it looks like a double arrow, you can zoom or squeeze. 310 • Well Engineering


Flow path display Activate the Flow path display icon to display the flow. If the well flows in both the tubing and the annulus, it will be modelled as two wells when exported for simulation.

By clicking the Toggle flow path display button in the function bar, you can turn on a flow path display.

Completions manager Completions

You can edit completion items from the Completions manager. Reservoir Engineering


You can view and edit completion items in a tabular view. To do so, either right-click the Global completions folder and select Completions manager, or click the Open completions manager button in the Well completion design process dialog. To sort the data, simply left-click one of the column headings. To reverse the order, click once more.

To organize the completions data in this tabular view, you have several options. You can grab a column header and drag it into the position you like. Alternatively, you can grab a column header into the dark grey area to group data by that column. Use the Columns drop-down menu to select which columns to display.



Completions manager Equipment tab

Use this tab to define equipment. The equipment defined here can be used by one or more completion items.

On the Equipment tab, you can define the equipment settings that can be used by several completion items in the project. For each equipment type, you must assign a name, outer diameter (OD), inner diameter (ID), inner roughness (IR), and outer roughness (OR). By clicking the Columns tab, you can add additional columns to specify more settings, such as drift diameter.



You can also edit the Completion data by opening the settings panel. You can do so by either right-clicking the completion item in the Input pane, or by right-clicking it in the well section window and then selecting Settings from the drop-down menu. On the settings panel for Casings, Tubings, Pumps, Chokes, Gas lift valves, and Inflow valves, you can select which equipment setting you want to assign.



Settings

Perforations

Give a depth directly or relative to a well

Give a start date

The connected cells within the perforation will be reported as single entry

Depth. If you want to place a completion item at the depth of a well top, you must put the Well top into the Depth field and then enter the number 0 into the box to the left of the drop field. This is because the depth entered here is the offset to the well top. Diameter. The diameter you enter here is in inches.



Depth interval

Place completions relative to well tops

Remember, for a designed well, you can make artificial well tops at the position where the well penetrates one of the horizons in the 3D grid. This is further explained in the “Well path design” lesson.



Event shifting

Global completion items Allows you to give a default direction of event shifting for each completion type.



Open hole default values Global completion settings

The default diameter for an open hole well is 7.5 inches. Change the number, or use a Calliper log to give a new default value.

Well completion design Operations

You can use the Operations tab to modify and make completion items.



You can use the Operations tab on the Well completions design process dialog to edit existing items or to add new completions.

One way to modify existing items is by changing the radius. New items can be added either for the whole well, or according to a well log. Discrete well logs with the correct template must be used as input for Petrel to understand which intervals to complete with which equipment.



Event data can be imported from file. Select between the formats Well event data to import perforations, stimulations and work-overs, and Well tubing data to import casings and tubings. You can also import completion logs and then use the Operations tab on the Well completion design process dialog to convert them into completion items.



Notice that if you are only importing perforations, you should select the check box Add casing to all wells with events. Otherwise, you will add perforation to a well which is open hole by default, and it will then be treated as open hole.



The previous slide shows the format of an events file with information on which data is required. For instance, if the well has been perforated, the event file should contain the top and bottom depth of the perforation. Petrel will translate the depth of events into the I, J, and K cell location, and the simulator will calculate the transmissibility between the well and the cell.

Completion items Time player

Use the Time player buttons to see the completions change through time.

Exercises – Well completion design In this exercise, we will complete the well we imported earlier with a casing and a perforation. We will use the Well completion design process in Petrel. We will also import well completion items. Exercise Workflow • Use the completions manager to define new equipment • Set up a well section window • Insert casing • Edit casing • Insert perforation



Exercise Data In this exercise, you will continue the project you have been working on in the previous modules and exercises. Exercise steps - Define equipment 1. Open the Completions manager dialog. You can access the Completions manager by right-clicking on the Global completions folder and selecting it from drop-down menu.

2. In the dialog that opens, go to the Equipment tab. 3. Click the Add a new row button , then select Casing and enter 1 as the number of equipment to be created. 4. Give the casing the name New equipment. Then, specify an outer diameter (OD) of 6.0 inches and an inner diameter (ID) of 5.5 inches.



5. Click Close to save the settings and to close the dialog. Exercise steps – Insert casing 1. Insert a new well section window with the Window > New well section window command. 2. Accept to create the new Well section template 2. 3. Now you see an empty well section window. Select the check box in front of well P08 in the Input pane, to display it in the window. This is the well we imported using the Reference project tool. We will use the well section window and the Well completion design process to create completion items for P08. 4. At the top of the well section window, select to show the depth track in measured depth (MD) and not in sub-sea true vertical depth (SSTVD).



5. Go to the Input pane and then expand the Global completions sub-folder located under the Wells folder. Select to view Casing and Perforation.

6. Next, select the check box in front the Well tops folder to display the well tops. 7. Activate the Well completion design process in the Well engineering folder on the Processes pane by clicking it once. The function toolbar appears with icons (tools) relevant to the completion design process.

Click the Add/edit casing icon and click inside the Completions track for well P08, Petrel will prompt you for a start date. Enter 2007-01-01.



Exercise steps – Edit casing 1. Hover the mouse pointer over the casing and see that it changes shape into a double arrow when you cross the base of the casing.

2. You can now click and drag the casing base up and down in the well section window. 3. Right-click inside the casing in the completion track and select Settings from the drop down menu. This opens the settings window for the casing. 4. In the settings window, go to the Properties tab. 5. Use the Equipment name drop-down menu to assign the New equipment to this well.

6. Select well P08 in the Input pane and drop it into the Bot. MD(m) field of the Properties tab. Then, type 0 in the field to the left to case the well all the way to the bottom. Click OK and observe how the casing is extended all the way to the bottom of the well.

Exercise steps – Insert perforation 1. From the well section window function toolbar, click the Add/ edit a perforation button . We will now insert a perforation that runs from the top of the reservoir to the bottom of the well. 2. Click in the well section track somewhere below the well top 326 • Well Engineering


representing the top of the reservoir. Petrel will ask for the start date for the perforation – type in 2007-01-01 – and click OK. 3. Display porosity from the upscaled grid along with the completion track. Drag the perforation to a depth with good porosity. You can also extend the perforation using the up-and-down cursor when hovering over the perforation at the very edge (top or bottom).  4. We will place the perforation relative to the nearest well top. Open up the Completions folder for the well P08 in the Input pane, right-click Perforation and select Place completions relative nearest top from the drop-down menu.

5. The perforation changes color to indicate that it is placed relative to the depth of the well top. 6. Right-click the perforation and open the settings. Go to the Depth / date tab and notice the top and bottom of the perforation interval has been set relative to the nearest well top. 7. In the Settings window, set the top interval depth to 0 to place the perforation exactly at the well top position. Click OK. Observe the change in the well section window.



8. Leave the well section window open.

Import well completion events The Global completions folder contains all of the completion items that exist for at least one of the wells, and is used as a filter when you are working with completions in a well section window, or to quickly see the types of completions that exist in the project. Exercise steps 1. Right-click on the Global completions folder and select Import (on selection). Set the file format to import to Well event data (Ascii) (*.ev).

2. In the Import file dialog, select the file Dataset > ImportData > Well_engineering > ImportWells.ev. This is the well event data file for the P07 and the P07%P08 branch. Click Open. 3. In the Import event data window, check that the Flow name in file are set to match the Petrel well traces. 328 • Well Engineering


4. Go to the Import settings tab, and enable the options Add to existing events and Add casing to all wells with events. Now, the import will not overwrite any existing events and the well will get a casing completion. 5. Select the Custom date format radio button, and specify the date format that you find in the file you are importing.

6. Inspect the third tab, Unknown data, to verify that there is no unknown data in the input file. Click OK to import the well completions for P07 and P07%P08. Reservoir Engineering


The completion items are added to the wells in a sub folder named Completions. Expand this folder to see which completions exist for the well.

At the bottom of the Petrel user interface there is a Time player toolbar. Click the First time step button to go to the first date. Step forward in time to see when each of the completion items are added.

Exercise steps - Examine the imported data: You should now quality check that Petrel has imported the well completions correctly. We will do this in a well section window. 1. In the active well section window, select to view the wells P07 and P07%P08 from the Input pane, deselect well P08. 2. Expand the Completions folder for both wells to see all of the completion items that were imported. 3. Select to view the completion items by selecting the check box in front of the Global completions folder. 4. Go to the Windows pane and expand the folder for the Well section window. Open the settings for the Well section window and under the Definition tab, set the Domain to measured depth (MD).Click Apply. 5. Select to view porosity together with the completions items to check that the perforations are in good porosity zones.

You can view the completion items in the 3D window. Click on the Global completions folder in the Input pane to view the completions for the wells.



Make completions using the Operations tab Exercise steps 1. Right-click the well P09, and select Import(on selection...). 2. Select to import a file of type Well logs (ASCII) . 3. Select to import the file Dataset>ImportData>WEll_ Engineering>P09perforation.txt. 4. In the import dialog that opens, make sure to match the column numbers correctly, then click OK.

5. Go to the Global well logs folder and rename the new log to Perf. 6. Open a well section window, accept to create a new well section template 3. 7. From the Input pane, expand the Global completions folder select Casing and Perforation. From the Global well logs select to view Perf.



8. Select to display well P09. You will see the Perf log that you just imported. Go to the Models pane and select to view porosity from the upscaled grid. 9. Open the Well completion design process, select the operation Create simple completions. 10. Drop the P09 well into the Wells field. 11. Change the date to 01/01/2012. 12. Select the options Create casing and Whole well. 13. Select the option Create perforation and From log. Drop in the Perf log you imported. 14. Deselect the options Create liner and Create completion string. 15. Click Apply to create the completions. Observe the new completion items in the well section window.





Summary In this section you learned how to add and import wells to the project. You first inserted a simple, vertical well, then looked into the process of digitizing well traces. Finally you learned how to place well into targets given as a discrete grid property automatically. Once the wells are in place in the project, they need to be completed. You learned how to use Petrel to add completions to the simulation case. We also looked into how to edit and manage different completion items both using the Well section window and the Completions manager.



Module 9 - Prediction strategies Introduction In this module, how to make prediction development strategies will be covered. It is also demonstrated how to use the Keyword editor to include features of ECLIPSE that are not yet available through the Petrel user interface. Prerequisites Basic knowledge of Petrel is required. Learning Objectives In this module you will learn how to: • Use the development strategy process • Insert and modify rules to an existing development strategy • Make a prediction strategy • Use restart runs to continue a simulation • Use the Keyword editor to modify cases


Prediction Strategies • 335

Lesson 1 - Prediction development strategy In this lesson, you will make a prediction development strategy. Furthermore, you will define a simulation case, using the end results after the history case, as your starting conditions.

History-Prediction History:

• Done to validate the model against history • Use observed rates as well control data • Use historic events; dates for perforations

Prediction:

• Used to predict future behavior • Gives the rates or pressures that the wells should be operated at forward in time

Make a strategy Use the toolbar to: Add times Add wells Add rules

336 • Prediction Strategies


Default strategies The Use presets drop-down menu offers four template strategies. Note that these are intended as starting points for creating a strategy, and in most cases they require further editing in order to work. • History strategy: Utilizes the first observed data set that is listed in the Global observed data folder. All wells in the project are added to the strategy. In many cases, no further editing is required to make a strategy for reproducing reservoir volume rates for all wells with observed data. • Empty prediction strategy: This will give you a blank strategy, the same as when the process is opened for the first time. • Prediction depletion strategy: This sets up a field for production with no injection. All wells are added to the strategy and placed under production group control. You must set field group production target, and start and end dates. It is recommended to set the minimum bottom hole pressure, and optionally, the maximum rate limits. • Prediction water flood strategy: This sets up a field for production with water injection. Group and well rules are setup for group production control and full voidage replacement. Petrel cannot detect which wells are producers and which are injectors. Therefore, you must drag producers to the PROD folder, and injectors to the INJ folder. In addition, you must set the field group production target and start and end dates. It is recommended to set bottom hole pressure limits, and optionally, maximum rate limits on both producers and injectors.



Add times

Add times if you want to specify different settings for different time periods.

You can add new times to the strategy, and then add new wells or new rules to existing wells from that time.

Add wells

You add a new well to the project by selecting it on the Input pane and clicking the blue arrow in the Make development strategy process dialog. Similarly, you can add a folder of wells. 338 • Prediction Strategies


Add wells

Linked folders

If you drop in a folder of wells from the Input pane, changes to that folder is going to take effect in the strategy.

Folders of wells are used to apply the same rule to numerous wells at a time. There are two types of folders: 1. Linked folders – are added by dropping a wells folder from the Input pane into the process dialog. The content is synchronized with the Input pane – you cannot edit those folders within the Make development strategy process, only delete the whole folder. This means that if you add a well to the folder on the Input pane, it will be included the next time the development strategy is exported to the simulator, without you having to rerun the process. 2. User folders – are added by clicking on the Add a new user defined folder button on the tool bar, and wells are added to the folders by dropping in the well from the Input pane, or by copy/paste or drag/drop within the strategy tree in the process window. To delete a well or a user folder of wells from the strategy tree, simply select it in the strategy tree and click the Delete key.


When you add wells to the strategy tree, their flow path is analyzed. If the well cannot flow at all – that is it is cased but has no perforations – it will not be added. If the well flows up both the tubing and the annulus, two well flows are added to the strategy tree.


Add new rules



Rules provide the simulator control parameters, and can generate one or more keywords. You can add rules with the Open ‘Add rules’ dialog button from the toolbar. This opens the rule selector dialog in which you can select one or more rules from a folder, adding them to the strategy tree. Right-click on the “rules folder” in the rule selector dialog to select alternative categorizations of the rules selector tree. The rule selector only shows rules valid for the current strategy type – history or prediction – and the currently enabled simulator(s). These choices are made by using the options at the top of the Make development strategy process dialog. Once a rule is added to the strategy, select it and it appears in the rule table. Enter numeric values, and select between the choices from the drop-down menus. Note that there are two types of blue arrows for dropping in. The conventional arrow is used just like the normal Petrel drop arrows and drop in data from the Input pane – observed data, well flow performance (VFP) tables, etc. The other arrow is used to drop items from within the strategy tree, such as wells, well folders and groups.

For more information on rules or rule validation, please refer to the Help Manual

Tabular rules



Sometimes, you need to set a parameter individually for several wells. For example, when you add a Well pressure production control, you may want to specify a different pressure for some of the wells. Start by creating a rule as usual, and drop in a folder containing all the wells into that rule. Enter all of the parameters. These will be the same for all the wells in the folder. Now right-click the rule and select Convert to tabular rule from the context menu. The tabular rule will show up as a folder of rules on the strategy tree. When you have selected the tabular rule, it will show one column per well in the rule table, allowing you to set individual values for each well.

Rules

Validation

Rules can be valid, invalid, partially valid, unsupported, or inactive. • A valid rule has all required parameters set. • A valid rule (with warning) is valid for all selected simulator but has at least one parameter set that is not supported for one of the simulators. Those are shown in blue on the strategy tree. 342 • Prediction Strategies


• An invalid rule has one or more required parameters missing. These are shown with a cross overlaid on their icon in the strategy tree. • A partially valid rule has all of its required parameters set, but is not supported by all enabled simulators. These are shown with an exclamation mark over their icon in the strategy tree. • Inactive rules are either not supported by any of the enabled simulators or the user has de-activated the rule by using the right-click menu. These are shown grayed out in the strategy tree.

Inactive or invalid rules will not be written to the simulation dataset when a case is exported.

The validation status and the icons are updated when you click Apply or OK, or for the active rule when you click Validate active rule. Select the report validation check box to have all validation messages copied to the Petrel message log once Apply or OK have been clicked. Note that a valid rule will not necessarily create a valid simulation. For example, many rules have several optional parameters and the simulator requires at least one of these to be set, but Petrel does not enforce this. Future versions of Petrel will enhance the validation logic.


Move the mouse over the rule’s icon in the strategy tree to see a pop-up with its validation report.


Group control

• Right-click the Groups folder to add new group. • Drag and drop wells between the groups.

The group structure can be changed at a later date – for example, to move a well from the producers group to the injectors group. Simply add the new control date, copy the groups folder to the new date, and edit the group structure accordingly.

Groups are used to tell the simulator how to control several wells at a time. Often, a group will correspond to a physical structure in the field, like a platform or a manifold – but it might as well just be a logical grouping – for example, all the wells producing from Zone 2. Petrel automatically adds wells to the default (first) group when they are added to the development strategy. You can then add groups using the Add new group button, and organize wells into groups by dragging and dropping between groups. To rename a group, select the group, right-click it and select Rename. It is important to distinguish between well folders and groups: • Well folders can be dropped in Wells parameters of rules. When exporting to the simulator, Petrel exports the rule to the simulator for every well in the folder. For example: set each well in a folder to produce 1,000 bbl/day. • Groups can be dropped in Groups parameters of rules. Upon exporting to the simulator, Petrel exports the rule to the simulator once for the group. The simulator works out how to apportion the rule to the members of the group. For example,



make the field produce 10,000 bbl/day from 10 wells – but it is up to the simulator to determine how much each well should contribute to the field target.

Groups

Membership changing with time • Add a new time • Add two groups • Add a group control rule for both time intervals • Assign the rule to one of the groups in each time interval



Edit and use • The strategy is stored on the Input pane. • Copy/Paste on the Input pane. • Drop into the Strategies tab of the Define simulation case process.

You can copy and paste a development strategy on the Input pane and then open the copy in the Make development strategy process to quickly recreate a similar strategy.

Use the solution at the end of a history case as start condition for a prediction run. Saves time as you do not recalculate pressure and saturation for the history period.

Field Production Rate

Restart runs Cell Saturations & Pressures recorded History Period

(Base Run)

Prediction Period

(Restart Run)

Time



Restart runs 1. Right-click on case that has been run, and select Insert restart case.

2. In the Define simulation case, select the restart case for edit.

Exercises – Prediction strategies In these exercises, we will create prediction development strategies using the Make development strategy process in Petrel. Exercise Workflow • Use a default strategy • Add a new rule to an existing strategy • Define a prediction case • View simulation results Exercise Data In the following exercise, we will continue on the project we created in the previously. Or you can use backup project Mod_8_Completed.pet.

Use a default strategy Exercise steps 1. Open the Make development strategy process. 2. Select Create new development strategy. 3. Click the Use presets button, and select Prediction water flood strategy. Reservoir Engineering


4. In the strategy tree of the process window, drag the producers into the PROD FOLDER and the injectors into the INJ folder. 5. At the top of the left panel, you find the start date. Doubleclick it and change the start date to 2009-02-01 . 6. Similarly, at the bottom of the left panel, there is a date subject. Double-click it to edit and select to run the simulation case for 5 years. 7. Click on the Group rate production control item in the Rules folder. Enter a Reservoir volume rate of 150000 m3/d, then use the drop-down menu to specify this rate as a target.

8. Click on the Group voidage replacement injection rule, and enter a Voidage replacement fraction of 1. 9. Next, click on the Well rate production control rule. Make sure that the PROD FOLDER is dropped in as Wells, and that 348 • Prediction Strategies


the control mode is Group control. Leave the remaining fields blank. 10. Click on the Well pressure production control. Again, the PROD FOLDER should be dropped in at the Wells field. Select Limits as Control mode from the drop-down menu. Specify a Bottom hole pressure limit of 100 bar. Leave the remaining fields blank.

11. Click on the Well water injection control rule. Check that the INJ FOLDER is dropped into the Wells field and that Control mode is set to Group control. Also, enter a Bottom hole pressure limit of 400 bar. 12. Finally, click on the Reporting frequency rule and select to report every sixth month. 13. Click Apply to save the development strategy.

Add a new rule to an existing strategy Exercise steps 1. If closed, open the Make development strategy process, and select Edit existing. 2. Select the water flood strategy you made in the previous exercise from the drop down list. 3. Click the Open ‘Add rules’ dialog button . 4. In the dialog that opens, left-click on the Well water cut rule located in the Wells folder. Click the Add rule button. Click Close. 5. In the new water cut rule, drop the PROD FOLDER into the Wells field. 6. Type in a Water cut limit of 0.9. 7. Select Close well as Water cut action by using the dropdown menu. Reservoir Engineering


8. Click the Validate active rule button to check the validity of your new rule. 9. Click OK to save your development strategy and to close down the process dialog.

Define a prediction case Exercise steps 1. Go to the Cases tab. Right-click the Aquifer case, and select Insert restart case. 2. Open the Define simulation case process from the Processes pane. 3. Select Edit existing case, and then select your restart case from the drop-down menu. Note that the settings under the Grid, Functions, Strategies tabs were preserved and that these settings are not editable. 4. Go to the Strategies tab. 5. Add a row to the table by clicking the Append item in the table button . 6. Select the Prediction waterflood strategy 1 on the Input pane, and drop it into the table by pressing the blue arrow . 7. Select 1st of February 2009 as Restart date. 8. Click Apply to save your case, then click Run to run the simulation.



View simulation results Exercise steps 1. Open a function window. 2. Go to the Cases pane and select both the aquifer case that you used to restart from and your new prediction case. 3. Go to the Results pane and select to view Pressure for the Field.

4. Use the same function window and deselect to view Pressure and select Oil production rate. 5. Deselect Filed identifier and select to view the Wells P05 and P09. 6. Notice how P09 starts to produce between 2011 and 2012. This is the reason of small pressure draw down in the previous plot.


If you want P09 to start producing when the perforations open for this well in 2012. Go to Event shifting under the Settings for Perforations>Depth/date tab>select Even shifting>Specify Date.


Make a strategy with a tabular rule - Optional Exercise steps 1. Open the Make development strategy process. 2. Select the radio button Create new development strategy. 3. Select Empty prediction strategy from the Use presets drop-down menu. 4. Give the new strategy a name, for instance “Tabular rule”. 5. Double-click on the start date and change it to 2009-02-01. 6. Double-click on the end-date and change it to 2014-02-01. 7. Click on the Report frequency rule, and select a Report frequency of 6 months. 8. Insert the Injectors, the Producers, and the Imported folder of wells from the Input pane. 9. Right-click the Wells folder inside the process dialog, and select Add new user folder.

10. Name the new folder All producers, then drag and drop the Producers and the Imported folders into it.

11. Right-click on both the Producers and the Imported folder (you can select both by pressing down CTRL) and select the Merge with parent folder. 12. Click the Add rules button to open the rules dialog. 352 • Prediction Strategies


13. Select to add a Group voidage replacement injection, a Well water injection control, a Well rate production control, and a Well pressure production control rule. Close the Add rules dialog. 14. Left-click on the Group voidage replacement injection rule and drop the group Field into the rule and select a Voidage replacement fraction of 1.

15. Left-click the Well water injection control rule and drop the Injectors folder into the Wells drop-field. Select Group control as control mode. 16. Left-click on the Well rate production control rule. Drop in the All producers folder into the Wells drop-field, select Reservoir rate as the Control mode, then type in a oil rate of 10000 m3/d.

17. Right-click the new Well rate production control rule in the Rules folder and select Convert to tabular rule from the drop-down menu.



18. In the tabular rule, change the Reservoir volume rate for wells P02, P05, P08, and P09 to 20000 m3/d.

19. Left-click on the Well pressure production control rule, and then drop in the All producers folder in the Wells field, then select Limit as the Control mode. 20. Enter a Bottom hole pressure limit of 100 bar. 21. Click OK to save the new strategy. Exercise steps 1. Go to the Cases tab. Right-click the aquifer case , and select Insert restart case. A new case, Aquifer_RESTART_1, appears on the Cases pane. 2. Open the Define simulation case process and select to edit the restart case you just created. 3. Go to the Strategies tab. 4. Add a row to the table by clicking the Append item in the table button . 5. On the Strategies tab, drop in your new strategy Tabular rule.

6. Click Apply to save the case, and Run to run it. 7. Open a function window, and examine the results. In particular, notice the rates of the producers. 354 • Prediction Strategies


Lesson 2 – Keyword editor

Keyword editor Some functionality is not yet available from the Petrel user interface and must be accessed by manually inserting keywords. In some cases, Petrel generates a keyword but the user want to do manual editing, e.g., conversion of ECLIPSE to Petrel project.

There are still some ECLIPSE and FRONTSIM functionalities that cannot be accessed through the Petrel user interface and hence the required keywords are not exported by Petrel. In such case, it is possible to add and edit the keyword as user keyword via the Editor. Reservoir Engineering


Keyword editor Examples are: • Thermal simulations • Simulator tuning • Output additional summary vectors

As an example, you can use the Keyword editor to report the elapsed time of a simulation run.

Keyword editor The Keyword editor is accessed from: • Advanced tab of the Define simulation case process, or • Cases pane. Right click a case and select Editor…



Keyword editor Sort by section

Sort by section: Keywords listed to the right belong to the ECLIPSE/FrontSim section selected to the left

When Sort by section is selected, the keyword editor shows: • Left: All keywords in the simulation deck sorted by section • Right: All available keywords. When a section heading is selected, the list is filtered so that only keywords belonging to that section are listed.

Keyword editor Sort by include file Sort by include files: the list on the left side shows the include files that can be edited

Expand by using the + besides the file name to list the keywords contained in the file.

When Sort by include files is selected, the left side of the Keyword editor shows the include files that can be edited. Double-click a file to open it in an editor. Reservoir Engineering


Keyword editor Inserting keywords The list on the right hand side contains all keywords for the highlighted section

Keywords can be inserted or removed using the Insert and Remove buttons.

To insert a new keyword: • Highlight the section where you want to insert the keyword • Select the keyword from the list to the right • Click Insert • Edit the new keyword in the editor that opens up • Move the keywords into the correct position in the section by clicking the Up or Down buttons.



Keyword editor Editing keywords

Right mouse select any keyword and select Edit to open the keyword in an editor. Double-clicking a keyword will also bring up that keyword in an editor.

You can either double-click or right-click a keyword and select Edit to open it in your default editor.

Keyword editor

Preserving keyword edits User keywords (black) Edits to these keywords are preserved. Petrel keywords (blue) Petrel is allowed to overwrite. Can be made into user keywords. Petrel keywords (red) Cannot be made into user keywords.



Petrel tags keywords and files to indicate how the keyword was created. The keywords are displayed in red, blue or black: • Blue: a Petrel generated keyword which is part of a file that can be edited by the user. • Black: a keyword that has been edited/inserted by the user. Petrel is not allowed to overwrite it, even if the settings are changed from the Petrel user interface. • Red: a file which is generated by Petrel that cannot be edited by the user. Petrel will overwrite the contents of this file regardless of whether the keywords contained in the file are marked as black or blue. In addition, section head keywords are shown in red. When Petrel creates a keyword it adds the following comment “ -- Generated : Petrel ”

This indicates that Petrel will overwrite this file and not preserve any changes made by the user. If you remove this comment, Petrel will not do any changes to the keyword it contains even if new input is given from the Petrel user interface. “--!!! Generated file. Any edits to this file will be lost on next export from Petrel.”

This indicates that Petrel will overwrite this file and not preserve any changes made by the user. If you remove this comment, Petrel will not do any changes to the keyword it contains even if new input is given from the Petrel user interface.



Keyword editor

Preserving keyword edits To make a Petrel keyword into a user keyword, blue to black: • Right-click the keyword and select User keyword OR, • Delete the comment line above the keyword.

Preserving keyword edits



You will notice that if you make a new simulation case by opening an existing case in the Define simulation case process and selecting Create new case, then all keywords that were inserted manually are lost. To make a new case containing all the new keywords, select the case on the Cases pane and press CTRL and C/CTRL and V to copy/ paste it. The copy can then be opened in the Define simulation case process for further edits.

Keyword documentation Right-click any keyword in the tree and select Documentation.

Right-click on any keyword in the Keyword editor and select Documentation to open the Eclipse/FrontSim manual for that keyword.



Import existing simulation case

Import a case - Select file Right-click in the Cases pane and select Import (on tree)…

1. Set Files of type to be ECLIPSE/FrontSim data and results. 2. Select .DATA, or .EGRID etc. and Petrel will locate the other files, if available.

A simulation data file, with or without results, can be loaded to Petrel in the Cases tab.

Import a case - Selection of files The Simulator is auto selected based on the data file. Make sure it is correct as it cannot be changed after import.

Petrel will locate all necessary files, if available. You can also make your own selection.



Assuming all the files have a common root name and are in the same directory, Petrel will identify them for loading.

Import a case - Units issues You will receive a warning if the project you import does not match the unit system of your current project.

Click on Change if your current project is empty.

The units cannot be changed after import.

Petrel will, by default, assume that the imported files have the unit system selected in the project settings. If you attempt to load a simulation case with data from another unit system, Petrel will warn you and ask whether you want to change the project units to match the incoming data. If you select to change the unit system, data that is already in the project will not be converted. Hence, it is only when you are importing a case into a new, empty project that you should select to change the unit system. Note that Petrel cannot do unit conversion after import. If you click on Continue, then: • The grid geometry and 3D properties imported into Petrel will be converted into project units • Summary line graphs imported into Petrel will be displayed in project units • The keyword data will remain in the original units



Customize units If you run the ECLIPSE case again from Petrel and load its results, the results will be converted to project units. Similarly, if you are creating cases within Petrel, you can customize the units in the Project > Project Settings > Units to be different in the simulator to the project units. Working in this mode will cause Petrel to convert keyword data on export, and results on load, between the simulator and the project units. You should be careful when you are working in a mixed unit mode! It is very easy to get confused and make mistakes.

Import a case – Petrel objects

CAUTION: These settings only apply on import and export. Changing the units in the templates or in the Project Settings after you have imported the data have no effect on the numbers, it simply changes the display label.

Well data from the RESTART files in the Input pane. Summary data and 3D Grid and properties in the Results pane. Simulation case added to the Cases pane.



Import a case - Convert to Petrel case You can convert the imported case to a Petrel case. Right-click the case and select Convert to Petrel case.

Most items are converted including: • Fluid model • Rock physics functions • 3D grid properties

The development strategies are NOT converted.

The SCHEDULE data is not converted to a development strategy in Petrel. You can still run the case from Petrel by right-clicking on the case in the Cases pane and select a Simulation run only. The SCHEDULE data will then be read from the file.



Examples of use of the Keyword editor

Keyword editor Summary vectors

Select the SUMMARY section.

Select the additional vectors you want, for example connection oil production for a well.

To report other summary vectors than the ones listed on the Report tab of the Define simulation case process, you can use the Keyword editor: • Select the SUMMARY section in the left part of the Keyword editor • Select the vector you want to report in the list on the right side • Check the syntax of the keyword in the manual if necessary • Click the Insert button and edit the keyword in the editor that opens



Keyword editor

Tuning the simulator Insert the TUNING keyword into the SCHEDULE section.

Default tuning is usually good enough for ECLIPSE. Use with caution.

If you need to make changes to the ECLIPSE time stepping or the convergence criteria, you must use the Keyword editor. In FrontSim there are several options for setting the tuning parameters for the simulator from the Advanced tab of the Define simulation case process.

Exercises –Keyword editor - import a case These exercises shows you how to use the Keyword editor to access the ECLIPSE/FrontSim keywords. Exercise Workflow • Import a simulation case • Edit the case using the Keyword editor • Convert to Petrel case Exercise Data In this exercise, you will open a new Petrel project and import an existing case from the folder ImportData>KeywordEditor.



Load a simulation case Exercise steps 1. Open Petrel, or start a new project if Petrel is already open. 2. Go to the Cases pane. 3. Right-click and select Import (on tree). 4. Ensure Files of type is set to ECLIPSE/FrontSim data and results (*.*) 5. Navigate to the folder ImportData > KeywordEditor containing BRILLIG.DATA. 6. Click on BRILLIG.DATA then click Open. This opens the Import ECLIPSE / FrontSim run dialog. 7. As there are no results, the only file to load is the .DATA file. Ensure the Simulator is set to ECLIPSE 100.

8. At the bottom of the Import ECLIPSE / FrontSim run dialog, deselect the Automate handling of import settings option. Click the Advanced button. 9. In the window that opens, select Global coordinate system. In the Remove cells part of the dialog, deselect to use Flat cells with no volume and pillars with equal z-values. Reservoir Engineering


10. Click OK. You will be prompted with a question asking whether you want to change the project coordinate system to match the import data. Click Change. The ECLIPSE file is loaded into Petrel. 11. Select to use NULL as coordinate system if prompted. 12. Save the project to the folder containing the BRILLIG data.

Edit the case

The list of keywords on the right side is sensitive to the section selected on the left. For example, click on GRID to see only the relevant keywords on the right hand side.


Exercise steps 1. Right-click the BRILLIG case on the Cases pane and select Editor to open the Keyword editor. 2. Expand the GRID section. Locate the NOGGF keyword. Rightclick it and select Documentation to get an explanation of the keyword and any associated parameters. 3. Close the documentation and remove the keyword from the case by selecting it and clicking the Remove button. 4. Click on Apply to save the changes. 5. Select Sort by include files in the Keyword editor. Reservoir Engineering

6. In the Keyword editor, scroll down the left hand side and highlight a keyword inside the SCHEDULE file (BRILLIG_SCH. INC).

7. Select the INCLUDE keyword from the right hand side and insert it in the left hand side by clicking Insert. 8. Enter the VFPI.TXT file in the INCLUDE file. The file contains VFP tables for your wells. Save and close the text file. 9. Click on OK to save the changes and to close the Keyword editor. 10. Save the project.

Run the simulation case Exercise steps 1. Right-click on the ECLIPSE 100 case again and select Simulation run only. 2. Browse the Input, Models, and Results panes. Expand the Simulation grid results folder in the Results pane, locate your case in the Cases pane and display the simulated properties in a 3D window (Dynamic folder). 3. Open a function window from the Window menu, expand the Dynamic results data folder in the Results pane. Ensure BRILLIG is selected for view on the Cases pane. 4. Review some of the summary data vectors. You may need to use the View all in viewport icon to see the entire data range.



Convert to Petrel case Exercise steps 1. Right-click on BRILLIG in the Cases pane and select Convert to Petrel case. 2. A message log will give you information on the keywords that could not be converted to Petrel objects. 3. Inspect the Input and the Models pane. A fluid model and rock physics functions has been added to the Input pane, and a new model containing 3D grid properties is added to the Models pane.



Summary How to set up prediction development strategies in Petrel has been covered in this module. How to add additional rules and organizing the wells into groups or folders of wells was covered. We have also covered the use of the Keyword editor to enable options that are not yet available inside the graphical user interface in Petrel.



Appendix 1 - Advanced Workflows Dual porosity – Dual permeability Dual porosity – Dual permeability Fluids exist in two interconnected systems.

Simulator approximation Reality

In a dual porosity reservoir, fluids exist in two interconnected systems: • The rock matrix, which usually provides the bulk of the reservoir volume • The highly permeable rock fractures. If the matrix blocks are linked only through the fracture system, this would conventionally be regarded as a dual porosity single permeability system, since fluid flow through the reservoir takes place only in the fracture network with the matrix blocks acting as sources. If there is the possibility of flow directly between neighboring matrix blocks, this is normally considered to be a dual porosity dual permeability system. Reservoir Engineering

Dual porosity dual permeability runs are computationally more expensive than dual porosity single permeability runs.

Appendix 1- Advanced Workflows • 375

To model such systems, Petrel will generate two grids – one representing the matrix and the other representing the fracture volumes of the cell. The porosity, permeability, depth (etc) properties of both grids may be independently defined. A matrix-fracture coupling transmissibility is constructed automatically to simulate flow between the two systems due to fluid expansion, gravity drainage, capillary pressure, etc. In a dual porosity run, the number of layers in the Z-direction should be doubled. The simulator associates the first half of the grid with the matrix blocks, and the second half with the fractures.

Dual porosity – Dual permeability Create fracture network model using the Create discrete fracture network process Scale up fracture network properties: porosity, permeability (3 or 6 tensors), sigma

The Scale up fracture network process converts the discrete fracture network (with its defined properties) into the properties that are essential for running a dual porosity, or dual permeability simulation, in ECLIPSE or any other simulator. These are fracture porosity, fracture permeability (3 or 6 tensors) and sigma factor (the connectivity between the fractures and the matrix).

376 • Appendix 1- Advanced Workflows


Dual porosity – Dual permeability Add fracture system to simulation:

3. Add relative permeability curves for the Fracture system

1. Select simulation type

4. Set Advanced dual porosity settings (no DP multiplier and Gravity drainage)

2. Drop in fracture properties and the dual porosity matrix-fracture coupling transmissibility

3

1

2

4

Sector modeling Sector modeling allows you to simulate a portion of a reservoir - the region of interest - using boundary conditions extracted from a (previously run) full field model. This is useful when planning an infill drill well, designing a complex completion or matching a well’s performance to observed behavior. The sector model simulation will run much faster than the full field model. There are two distinct workflows for sector modeling. The main difference is whether the regions used to identify the region of interest are defined before or after the full field run is performed. Regions defined before running the full field model allow the boundary conditions to be captured by the simulator at every time step during the full field run, and results in a more accurate sector model simulation.



To define a region, you can use the Geometrical modeling tool. In this example, a region around well P03 is created.



The previous illustration shows where to insert the region of interest in the Define simulation case process dialog in order to capture the boundary conditions for a well region during a full field run.

Sector modeling Insert a sector model

Once the full field model has run, the boundary condition for the region is stored on the Models pane.

Right-click the full field case in the Cases pane and select Insert sector model.

Once the simulation has run and the results are loaded, a new folder is added to the Models pane. This folder is named Sector modeling and contains the boundary condition that was captured at the boundary of the region that was used as input. To insert a sector model, right-click on the full field model in the Cases pane and select Insert sector model. A new case is then added to the Cases pane. You can open the case in the Define simulation case process to supply the boundary condition.



Sector modeling Run a sector model

Open the Sector modeling in the Define simulation case model, and drop in the boundary condition captured during the full field run.

Hysteresis

Hysteresis

Hysteresis: When the curve used to determine the rock properties is a function of the history of the rock and a function of the direction of the change in the saturation.

Hysteresis enables you to specify different saturation functions for drainage (decreasing wetting phase saturation) and imbibition (increasing wetting phase saturation) processes for the simulation case. A typical pair of relative permeability curves for a non-wetting phase is shown in the figure. The curve 1 to 2 represents the user supplied 380 • Appendix 1- Advanced Workflows


drainage relative permeability table, and the curve 2 to 3 represents the user supplied imbibition relative permeability table. (Note that nonwetting phase saturation increases from right to left in this diagram). The critical saturation of the imbibition curve (Sncri) is greater than that of the drainage curve (Sncrd). The two curves must meet at the maximum saturation value (Snmax). The primary drainage curve is for a process which starts at the maximum possible wetting phase saturation (Swmaxd). If the wetting phase saturation decreases to (Swmin), this primary drainage curve is used. In a similar way, if the initial saturation is (Swmin), and the wetting phase saturation increases to (Swmaxi), the imbibition table data will be used. If the drainage or imbibition process is reversed at some point, the data used does not simply run back over its previous values but runs along a scanning curve.

Hysteresis Select drainage relative permeability curves and imbibitions relative permeability curves in the Functions tab. Drop in saturation functions from the Input pane.

For cases with the water saturation increasing: Imbibition curves should be used. When (in a grid block) the saturation of water increases and then the saturation of gas increases – Hysteresis should be used. You supply two saturation function tables for the simulation case. Reservoir Engineering


These provide respectively the primary drainage and pendular imbibition curves.

Case management Remote job submission It is possible to submit jobs from Petrel to a Linux/Unix computer.

To do so you must: • Install support for remote simulation • Configure Petrel for remote job submission • Define queues in Petrel

Remote job submission Petrel can run simulations in ECLIPSE and FrontSim either on your local PC, or on a remote server. In either case, you must have an installation of ECLIPSE Simulators on your PC, version 2006.1 or newer: this includes an application called eclrun.exe which is used by Petrel to submit simulation runs. If you wish to submit runs to a remote machine, you need to configure both Petrel and the server. See the Online Help for more information.



Index

B Based on input data, 155 Base surface, 52 Binary grid data, 118

Symbols

Bitlock, 40

3D grid skeleton grid, defined, 49 defined, 14

Black oil models, 67

3D viewing, 123 1D filters, 124 creating intersection window, 128 how to apply filters, 129 how to make filters using a Histogram window, 131 how to use I, J, and K filters, 131 how to view data on an intersection plane, 133 inserting intersections, 128 multi-value probe, 134 results viewing, 129 ternary property, user filters, 126 well filters, 126 +/- Sign, 27

A Active item, 26 Advanced tab selecting formats, 118 Algorithms for discrete properties, 168 in scale up properties, 166 Aquifers, 195. See

also Make aquifers;

adding, 203 Averaging (cell count) in scale up properties, 166 Averaging methods in scale up properties, 167 Averaging (volume-weighted) in scale up properties, 166

Reservoir Engineering Course

by manual settings, 72 dead oil, 72 default models, 72 dry gas, 72 gas properties, 73 heavy oil+gas, 72 how to plot, 83 importing a keyword fluid model, 83 importing fluid models, 81 initial conditions, 75 light oil+gas, 72 make contacts, 77 making a table with initial conditions, 76 oil properties, 74 separator conditions, 72 specifying fluid phase, 72 using a spreadsheet to model the variation with depth, 78 Bold Item, 26 Boundary in pillar gridding, defined, 141 Boundary for the Pillar grid defined, 14 Branching wells importing, 266 Bubble plots for observed data, development strategies and simulation data, 234 Bubble point line, 68 Bubble point pressure, 78

Index • 383

C

D

Capillary pressure, 95

Dead oil, 72

Cartesian Dx, Dy, Dz, 183

Define simulation case, 108

Cartesian Gradual Dx, Dy, Dz, 183 Cartesian Gradual Nx, Ny, Nz, 183 Cartesian Nx, Ny, Nz, 183 Cases pane, 26, 27 defined, 14 Casing, 306 Cell defined, 14 Cell angles, 157 cell inside-out, 158 Colors specifying line styles for simulation results, development strategies and observed data, 227 Comments tab, 34 Compaction rock compaction function, 89 Completions. See Well completion design Components tab adding new, 70 Compositional fluid model, 67 making, 70 Conditions initial conditions for black oil models, 75 Contact level, 78 defined, 14 Contact set, 75 Corey correlations in make rock physics functions, 92 Corner point grid defined, 14 Correlation library, 66 Create a STOIIP map from volume calculation,

advanced tab, 118 selecting grid type, 118 Depth placing completion items at depth, 315 Development strategies, 208 adding a rule to limit the production pressures, 222 averaging data, 216 bubble plots, 234 combining view-ports in one plot window, 238 default strategies, 212 defining a history case, 217 defining and running simulation cases using history development strategy, 223 exporting simulation results, 231 filtering results tree, 230 history match, 208 history strategies, 209 how to change the line style in function windows, 236 how to create a history strategy, 213 how to import observed data, 217 how to make a history development strategy, 217 how to visualize the observed data, 219 importing observed data, 210 line styles, 227 plotting, 215 plotting data, 226 prediction mode, 209 selecting, 108 viewing observed data in a function window, 212 view the history development strategy data, 221 water cut, 244 Deviation file importing, 265 Dew point, 78 Dew point line, 68 Digitizing fault, 56 well paths, 272

Critical point, 68 384 • Index


Directional averaging in scale up permeability, 167

how to use I, J, and K filters for 3D viewing, 131 how to use value filter, 162 making from function and histogram windows, 126 streamlines, , 235 well filters for 3D viewing, 126

Directions defined, 14 Discontinuous surface, 52 Dongle, 40 Dry gas, 72 Dual porosity dual permeability systems, 375

E Eclipse importing keyword files, 81 remote job submission, 382 Empty prediction strategy defined, 337

zone filter, 53 Flow-based upscaling in scale up permability, 167 Flow paths turning on display, 311 Fluid models ; See also Make fluid model assigning separate to regions, 112 compositional model, 70 making, 69

Endwell filter, 236

Fluids specifying fluids phase in black oil models, 72

Equality+/-, 251

Follow base, 54

Equilibration, 113

Follow top, 54

Equipment tab defining settings, 313

Formats

Erosional surfaces, 52

Fractions, 54

Event data

FrontSim

for exporting grid data from models pane, 118

importing perforations, stimulations and work-overs, 320 Explorer panes, 25

F Fault defined, 14 Fault filter defined, 53 Faults assigning transmissibility multiplier, 58 excluding in pillar gridding, 146 how to insert into grid, 57 how to make a simulation fault, 61 in pillar gridding, defined, 141 inserting into grid, 56 Filters defined, 14 fault filter, 53 how to make filters using a Histogram window, 131 Reservoir Engineering

remote job submissions, 382 Function bar, , 28 defined, 15 Function window defined, 15

G Gas properties, 73 General intersections creating intersection window, 128 inserting, 128 viewing data on an intersection plane, 133 General surface, 52 General tab used in black oil models, 72 Grayed-out area, 28

Index • 385

Grids creatings grids without faults, 48 how to make a simple grid, 48, 59 Skeleton grid, defined, 49 Grid separate zones in local grid refinements, 184

H Heavy oil+gas, 72 Help manual. See Online help manual Histogram window defined, 15 History matching, 208 crossplotting two vectors, 254 how to compare cases in a map window, 260 how to run history match analysis, 256 how to view match data in a function window, 259 how to view match data in a map window, 257 match values in map window, 252 normalization, 248 results viewing, 248 sampling, 246 settings, 245 setting threshold and equality, 251 single vector versus case number, 255 statistics settings, 254 viewing data in a function window, 249 viewing data in a map window, 249 zero data filtering, 248 History strategies, 209 adding a rule to limit the production pressures, 222 defined, , 337 defining a history case, 217 defining and running simulation cases, 223 editing default rules, 215 how to create, 213 how to import observed data, 217 how to make a history development strategy, 217 how to visualize the observed data, 219 plotting data, 226 viewing the development strategy data, 221 History tab, 34

386 • Index

Horizons. See also Make horizons base surface, 52 defined, 15 discontinuous surface, 52 erosional surfaces, 52 general surface, 52 inserting into simple grid, 50 make horizons process, 51, 52 types of, 52 Horizontal wells, 308 Hysteresis, 380

I Icons used in this manual, 13 Importing a polygon, 190 branching wells, 266 fluid models, 81 rock physics functions, 97 well header, 264 well path deviation, , 276 well path / deviation file, 265 Info tab, 34 Initial conditions tab, 75 Initializing the model 3D initial properties, 116 by equilibration, 113 methods for, 110 model, 108 with fluid and rock physics functions, 120 Input pane, 25, 26 defined, 15 Insert horizons, 50 Interface, 41 Intersection defined, 15 Intersection window defined, 15 Irreducible saturations, 94


K

grid to well connections, 185 methods, 183 scaling up a property onto the local grid set, 187 setting different parameters for different sources, 185 setting source parameters, 184 specifying host cells from sources, 182 upscaling a property, 193 use active filter, 184 zone filter, 184

Key Pillars, 140 Keyword editor, 355 defined, 15 documentation, 362 how to convert to Petrel case, 372 how to edit the simulation case, 370 how to load a simulation case, 369 how to run the simulation case, 371 inserting a new keyword:, 358 preserving keyword edits, 362 setting the tuning parameters for simulator, 368 sorting by include files, 357 sorting by section, 357 summary vectors, 367 tagging keywords, 360

L Layering, 51 follow base, 54 follow top, 54 fractions, 54 process, 54 proportional, 54 settings for scale up structure, 155 Layers defined, 15 LGR defined, 15 Licenses, 40 Light oil+gas, 72 Liner, 306 Line styles settings for dynamic data, 227 Local grid refinement defined, 15 Local grid refinements, 47, 180, 195 defined by polygons, 181 defined by surfaces, 181 defined by wells, 181 extending host cell along I, J, K, 184 grid separate zones, 184 Reservoir Engineering

Local grid set how to make, 190 inspecting, 192

M Make aquifers, 195 adding an aquifer, 203 creating new or edit existing, 196 drive direction and vertical extent, 198 properties tab, 202 specifying the model to use, 197 Make contacts, 77 procedure, 77 Make fluid model, 66 importing a keyword fluid model, 83 Make Horizons, 51 process defined, 51 Make rock physics functions, 88 capillary pressure, 95 corey correlations, 92 how to make, 100 how to make a saturation function, 98 importing, 97 irreducible saturations, 94 plotting, 97 Reviewing the data, 102 rock compaction function, 89 saturation function, 91 spreadsheets, 95 Make simple grid, 48 Make zones process defined, 51 Index • 387

Map window defined, 15 Menu bar, defined, 15 Model defined, 16

windows pane, 26, 29 workflows pane, 25, 29 Perforation, 306 Permeabilities directional averaging methods, 169

Models pane, 25, 26 defined, 16 Multiple drop, 52 Multi-value probe, 134

N Nodes defined, 16 Notes comments tab, 34

O Objects history, 34 renaming, 34 settings, 33 Observed data bubble plots, 234 change the line style in function windows, 236 importing, 210 viewing in a function window, 212 Oil properties, 74 Online Help Manual, 41 Opening projects, 39

Phase diagrams, 68 Phase pressures computing, 114 Pillar gridding boundary, defined, 141 cell size, 144 changing the grid orientation, 151 coarsening the grid, 148 concept, 140 defined, 16 excluding faults, 146 faults, defined, 141 geometry and formats, 147 results, 147 segments, defined, 141 settings, 142 throughput problems, trends, defined, 141 Pillars defined, 16 Plotting fluid model, 83 observed data versus the development strategy, 215 rock physics functions, 97 Plot window combining view-ports in one plot window, 238

OPF (Open Petrel Format) format, 118

Plug, 307

P

Polygons

Panes cases pane, 26, 27 input pane, 25, 26 models pane, 25, 26 processes pane, 25, 28 results pane, 25, 27 templates pane, 25 388 • Index

defined, 16 importing, 190 in local grid refinements, 181 in make aquifer, 197 Pore volume setting minimum, 119 Reservoir Engineering

Prediction depletion strategy defined, 337

R

Prediction development strategy adding new rules, 341 adding new times, 338 adding new wells, 338

Relative permeability curve for oil-water, 94

converting to tabular rule, 342 copy and paste a development strategy, 346 group control, 344 how to add a new rule to an existing strategy, 349 how to create by using a default strategy, 347 how to define a prediction case, 350 how to make a strategy with a tabular rule, 351 how to view simulation results, 350 linked folders, 339 making a strategy, 336 rule validation, 342 user folders, 339

Reference project tool how to use, 285

Remote job submission, 382 Reservoir conditions in black oil models, 72 Results 3D initial properties, 116 Results pane, 25, 27 defined, 16 exporting simulation results, 231 filter results tree, 230 Results viewing, 129 Rock compaction function, 89 how to make, 100 settings, 90

Prediction mode, 209 Prediction water flood strategy defined, 337

Rock physics functions. See Make rock physics functions Rules converting to tabular rule, 342 for the prediction development strategy, 341 validation, 342

Pressure entering at separator conditions, 72 Processes pane, 25, 28 defined, 16 Project settings, 31 Properties entering for gas, 73 for gas, 73 for oil, 74 multi-value probe, 134 Scaling up, 163 Proportional layering, 54

Q Qualitative mode, 250 Quality checking in scale up structure, 160 of the coarse grid, 156 Quantitative mode, 250 Reservoir Engineering

S Saturation by equilibration, 115 Saturation function, 91 how to make, 98 Saving projects, 39 Scale up. See

also Upscaling

Scale up fracture network, 376 Scale up properties algorithms for discrete properties, 168 applying different methods, 173 averaging methods, 167 how to sample properties from fine grid into coarse grid, 170 process, 163 reviewing in a 3D window, 175 Index • 389

reviewing the upscaled properties, 174 selecting algorithm, 166 Scale up structure, grid quality check, 160 layering, 159 two methods for, 155 Sector modeling, 377 capturing boundary conditions for a region, 378 inserting a sector model, 379 Segment filter used in local grid refinements, 184 Segments in pillar gridding, defined, 141 Segments (Regions) defined, 16

Simulators selecting, 108 Skeleton defined, 17 Skeleton grid, 147 Spreadsheet for wells, 297 Spreadsheets for rock physics functions, 95 to model variation with depth in black oil models, 78 Squeeze, 306 Startwell filter, , 236 Statistics tab, 35

Select/pick mode, 37

Status bar defined, 17

Sensitivity runs, 209

Stimulation, 306

Separator conditions, 72

Strategies

Settings for layering in zones, 155 for objects, 33 for pillar gridding, 142 for project, 31 for rock compaction function, 90 style tab, 33 Simulation case define simulation case, 108 importing an existing case, 363 managing, 366 remote job submission, 382 results viewing, 129 units, 364 Simulation grid defined, 17 making, 139 Simulations bubble plots for simulation data, 234 change the line style for simulated data in function windows, 236 development strategies, 208 viewing data on streamlines, 241 390 • Index

when initializing model, 116 Streamlines, 235 Style tab, 33 Summation in scale up properties, 166 Surfaces. See also Horizons defined, 17 in local grid refinements, 181

T Table setting up for initial conditions, 76 Temperature entering at separator conditions, 72 Templates changing, 34 defined, 17 Templates pane, 25 defined, 17 Terminology used in this manual, 13 Threshold, 251 Reservoir Engineering

Time units, 32

W

Title bar

Water cut

defined, 17

defined, 244

Toolbar defined, 17

Water rates, 244

Trajectories, 270 Transmissibilities tab, 119 Transmissibility multiplier assigning to fault, 58 defined, 17 Trends defined, 17 in pillar gridding, defined, 141 Tuning runs, 209

U Uncertainty workflow editor, 29 Units for time in Petrel, 32 Upscaling, 153 Use active filter in local grid refinements, 184 User interface, 24, 41

V Value filter how to use, 162 Vertical coarsening upscaling, 153 Vertical subdivision, 51 two methods for simulation grid, 155 Vertical well how to make, 278 Vertical well intersection inserting, 302 View Mode, 37 Visualization windows for, 29 Visualization windows, 36 Reservoir Engineering

Weighting defined, 17 Well bore history, 209 Well completion design, 306 editing completion data, 314 editing completion items, 310 editing existing and adding new completions, 319 how to define equipment, 323 how to edit casing, 326 how to import well completion events, 328 how to insert casing, 324 how to insert perforation, 326 how to make completions using the operations tab, 331 importing event data, 320 inserting a new completion item, 310 organizing data, 312 placing items at depth, 315 quality check, 330 Well data how to import, 276 importing a well header, 264 importing well path / deviation file, 265 Well filters, 126 Well header importing, 264 Well manager, 267, 303 Well path digitizing, 272 importing, 265 Well path design, 267, 286 editing, 275 inserting vertical well intersection, 302 intersection with horizons, 303 making a new vertical well, 268 process, 269 Index • 391

synthetic log curves, 302 trajectory, 270 Well path deviation how to import, 276 Well region property defining a region, 378 Well report how to make, 304 Wells in local grid refinements, 181 Well section window defined, 18 Wells spreadsheet, 297 Well tops defined, 18 Well trajectories defined, 18 Windows pane, 26, 29 defined, 18 Workflow for Petrel reservoir engineering, 21 Workflow diagram, 19 Workflow editor, 29 Workflows pane, 25, 29 defined, 18

Z Zonation, 155 Zone filter defined, 53 in local grid refinements, 184 Zones defined, 18 make zones process, 51

392 • Index


Petrel 2010 Reservoir Engineering Course

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