RESERVOIR ENGINEERING LAB MANUAL
2015-2016
UNIVERSITY OF PETROLEUM & ENERGY STUDIES DEHRADUN
DEPARTMENT OF PETROLEUM ENGINEERING & EARTH SCIENCES COLLEGE COLLEGE OF ENGINEERING ENGINEERIN G
UPES Ca Campus mpus “Energy Acres” P.O. Bidholi, Bidholi, Via Prem Nagar Dehradun -248 007 (U K)
Tel: +91-13 +91 -135-2776092-94 5-2776092-94 Fax: +91 135 135-- 27760904 27760904 Web: www.upes.a www. upes.ac.in c.in
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Reservoir Rock Properties Analysis COURSE OVERVIEW INTRODUCTION
LIST LIST OF EXPERIMENTS EXPERIMENT NO. 1:- To Plug a Core Sample from a Rock Block using Plugging machine machine and meas measure ure diamete diameterr of the core sample plugged. plugged. EXPERIMENT EXPERIMENT NO. 2 :- To Trim the Core sample (obtained from plugging machine) using Trim Saw Sa w machine machine and measure measure its length.
the core sample in Soxh So xhletio letion n Extraction Unit Unit EXPERIM EXPERIMENT ENT NO. 3: - To Clean the
EXPERIMENT NO. 4:- To fin find d the Porosity Poros ity of o f the core co re sample using using Helium Helium Porosimeter.
find the Perm Per meability ea bility of the core cor e sample sample using using Liqui Liquid d EXPERIMENT NO. 5:- To find Permeameter. EXPERIMENT NO. 6:- To find find the Permeabilit Pe rmeability y of the core sample using using Gas Permeameter. EXPERIMENT NO. 7:- To find find the Resi Res istivity st ivity,, format format ion factor facto r and cementati cementat ion e xponent of the core sample using using EPSA Resistivity Resistivit y Meter. Mete r. EXPERIMENT NO. 8:- Experiments will be carried out with the given - Graphs so as to solve particular Numerical Problems in various petroleum engineering disciplines EXPERIMENT NO. 9:- To find the capillary pressure curve using centrifuge (instrument needs to be checked)
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Reservoir Rock Properties Analysis COURSE OVERVIEW INTRODUCTION
LIST LIST OF EXPERIMENTS EXPERIMENT NO. 1:- To Plug a Core Sample from a Rock Block using Plugging machine machine and meas measure ure diamete diameterr of the core sample plugged. plugged. EXPERIMENT EXPERIMENT NO. 2 :- To Trim the Core sample (obtained from plugging machine) using Trim Saw Sa w machine machine and measure measure its length.
the core sample in Soxh So xhletio letion n Extraction Unit Unit EXPERIM EXPERIMENT ENT NO. 3: - To Clean the
EXPERIMENT NO. 4:- To fin find d the Porosity Poros ity of o f the core co re sample using using Helium Helium Porosimeter.
find the Perm Per meability ea bility of the core cor e sample sample using using Liqui Liquid d EXPERIMENT NO. 5:- To find Permeameter. EXPERIMENT NO. 6:- To find find the Permeabilit Pe rmeability y of the core sample using using Gas Permeameter. EXPERIMENT NO. 7:- To find find the Resi Res istivity st ivity,, format format ion factor facto r and cementati cementat ion e xponent of the core sample using using EPSA Resistivity Resistivit y Meter. Mete r. EXPERIMENT NO. 8:- Experiments will be carried out with the given - Graphs so as to solve particular Numerical Problems in various petroleum engineering disciplines EXPERIMENT NO. 9:- To find the capillary pressure curve using centrifuge (instrument needs to be checked)
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Course Overview This course provides an introduction to reservoir rock properties as determined by core analysis. Part of this course introduces the laboratory equipments as well as the procedures used for the core analysis. The theoretical aspects of the parameters used in the core analysis are also also briefly briefly descri desc ribed. bed.
The aim of this lab exercise is to get familiar with of the main rock parameters, how they are measured and the possible sources of errors in the results obtained from the laboratory measureme measuremen nts. At th t he en e nd of o f this cou co urse, o ne will have hands on experi exper ience on core plugging, trimming, cleaning and measuring the porosity, permeability, resistivity and possibly capillary pressures. These values are needed in reservoir engineering. One would also learn about errors in measurements.
Introduction Knowledge of the physical properties of the rock and interaction between hydrocarbons and the formation rock is crucial in understanding and evaluating the performance of a given reservoir. This information is usually obtained from two main sources: core analysis and well logging. In this manual we describe the core analysis. A core is a solid cylinder of rock
about 1, 1.5 or 3 inches in diameter and usually 30 feet in length. It is obtained by replacing the drill bit by a “core bit” which is capable of grinding the periphery of the rock keeping intact the inner core which is retrieved as a heavy cylindrical rock. Once the core is retrieved it is crucial to proper ly handle handle (to a void breaking break ing and any oth ot her kind of o f damag dama ge) the core. It is preserved preserved by avoiding e xposure to air. When the core arrives arr ives in the laboratory p lugs are usually drilled 20-30 cm apart throughout the reservoir interval. Then the plugs are analyzed by obtaining obta ining porosity, poros ity, permeability, fluid satu sat urati rat ions, grain density, resistivity and mineralogy. This analysis, which is performed at high sampling frequency and low cost, is called routine core analysis . The results from routine core analysis are used in interpretation and evaluation of the reservoir. Examples are prediction of gas, oil and water fluid contacts and volume in place, definition of completion intervals and fluid production rates. There are other important measurements with the aim of obtaining the detailed information about the multiphase flow behavior. This analysis, which is performed at low sampling frequency due 3
to high cost and more time need, is called special core analysis . Special core analysis gives information about the rock wettability, the distribution of oil, gas, and water in the reservoir (capillary pressure data), residual oil saturation and multiphase flow characteristics (function of capillary pressure and relative permeability). Measurements of electrical and acoustic properties, which are mainly used in t he interpretat ion o f well logs, are occasionally included in special core analysis.
The outline of this handout is organized as follows: We first describe the main pre-process ing steps that are considered on the core samples preparation (experiments 1 and 2). In experiment 3 we describe the core cleaning method, which is required before core analysis tests, as well as the saturation determination methods. In experiment 4, the porosity measurement technique is described and the instrument available in the laboratory for the determination of the core porosity is described. In experiments 5 and 6, we describe the techniques to measure liquid and gas permeabilities respectively. In experiment 7, we describe the core sample resistivity measurements. Experiments 8 and 9 are under construction. The instruments available in the reservoir laboratory and their capabilities are presented below:
Existing Laboratory Equipments No. 1
Name of Equipment Plugging Machine
2
Trim saw
3
Helium Porosimeter
4
Liquid Permeameter
5
Gas Permeameter
6
Centrifuge
7
Electrical Properties system Atmospheric
Application To plug a core sample from core specimens of different diameters or from blocks of a similar size. This machine is a bench model designed to produce fast, high quality sliced samples from all materials without disturbing the structure of the sample. To find porosity of core sample using Helium Porosimeter To find the permeability of given core sample using Liquid Permeameter To find the permeability of given core sample using Gas Permeameter Determination of capillary pressure at various fluid saturations. To find resistivity, formation factor and cementation exponent of core sample.
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EXPERIMENT NO. 1 Aim / Objective:- To Plug a Core Sample from a Rock Block using Plugging machine and measuring the diameter of the core sample plugged.
Apparatus Used:- Plugging Machine. Description of Machine The machine can accommodate cores measuring from 1” (1 inch) to 1.5”. A swivel joint with a tap allow internal irrigation of the core drill and a hose fitted with a tap allows external irrigation of the core drill. The speed can be adjusted by repositioning the belt (1800 rpm – 2500 rpm – 3500 rpm) like core slabbing machine. The machine comprises of: clamping stand column Spindle-Motor unit adjustable tilting table protective housing clamping unit recycling tank
Table of machine has a rotating capability up to 45º. This capability causes that user can make plugs from any part of slab even deviated sides.
Specifications Features
Value
Drilling Capacity (mm)
23
Tapping Capacity (mm)
14
Spindle nose
CM2
Quick stoke (mm)
110
Spindle Speeds
Variable
Speeds (rd/min)
250-4000
Spindle Motor KW
.66/1.1
Column diameter (mm)
100
Distance spindle to Column (mm)
235
Distance spindle to table maxi (mm)
823
Distance spindle to table mini (mm)
110
Distance spindle to ground table (mm)
1225
5
Table surface
300×300
Figure 1: Core plugging machine
Maintenance of Machine:1. Core plug unit
·
keep the unit and the protective housings clean
·
remove debris and core particles
·
remove sludge
·
clean all moving parts
2. Recycling Tank
·
change the cooling fluid as soon as it is dirty
·
make sure that the machine is disconnected
·
remove the pump and the waste pipe from the recycling tank
·
empty the tanks
·
clean the tanks and the separators
·
fill the tank with cooling fluid 6
·
refit the pump and the waste pipe to the recycling tank
3. Changing the Belt ·
Make sure that the machine is disconnected
·
Open the pulley cover
·
Loosen the 2 clamping screws and the belt tensioning lever
·
Pinch together the 2 sides of the spindle belt
·
Change the belts
·
Tighten the belts with the lever and lock the 2 screws
·
Close the cover
4. Disass embly of quill spindle
·
Remove the lowering shaft
·
Loosen the collar 1
·
Undo both screws and remove guide pin 3. Hold the quill during this operation
·
Remove the quill-sp indle from its bore
·
Unscrew and remove the cap 4
·
Remove nut 5, washer 6 and drive out spindle 8 downwards using a wooden mallet
·
If necessary, pull out ball bearings 7
· T slots (number- dimension- distance)
2/14- 200
Height (mm)
1800
Surface on ground
410×820
Weight (Kg)
210
Noise level
Under 70db (A)
Experiment operation First Use:· Check the tension on the pulleys · Check the direction of the spindle · Fill the recycling tank · Screw down the core drill and lock it in place · Mount a core sample and lock it firmly in the clamping unit · Adjust the lower stop on the core drill. 1- 2 mm before the end of slab is sufficient for · Prevention of plugging the sample in plug driller. Touching of the driller with table causes severe damage to the driller. · Close the core drill protective housing · Press the Start button 7
· · · · ·
Open the irrigation taps Check the flows Cut the core sample Press the « Stop » button Unclamp the core sample
Speed Selection:-
Speed of rotation can be adjusted by changing pulleys. The procedure for this operation is as: · · · · · ·
open the pulley cover loosen the 2 locking screws and pulley tension lever pinch together the two sides of the spindle belt change the position of the belt tighten the belts with the lever and lock the two screws in place close the cover
If the tension of pulleys is not sufficient then the belt should be changed. The procedure for changing the belt is as follow: · · · · · · ·
make sure that the machine is disconnected open the pulley cover loosen the two clamping screws and the belt tensioning lever pinch together the two sides of the spindle belt change the belts tighten the belts with the lever and lock the two screws close the cover
Figure-2:- Plugged Core Sample
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EXPERIMENT NO. 2
Aim / Objective: - To Trim a Core sample (obtained from plugging machine) using Trim Saw machine and measure its length.
Apparatus Used: - Trim Saw Machine Introduction After preparing plugs from core drill machine, all of them should be cut into desired size. This can be done by trimming machine. Trimming machine is a bench model designed to produce fast, high quality thin sliced samples from all materials without disturbing the structure of the sample (Fig. 3).
Figure 3: Trimming core plug machine
However, note the following safety notices: ·
Touching any resinous cutting wheel can be dangerous.
·
The machine is fitted with safety devices which prevent the wheel from turning when the hood is open
·
This machine must only be used by a qualified person who has received the proper training
·
required to achieve the quality of cut and the high standard of safety envisaged by the manufacturer. 9
Machine Description:The basic model can work either in manual feed or with an optional hydraulic automatic feed which is driven by the domestic water supply (Minimum pressure 1.5 bars). In the automatic mode, user can determine the speed of rotation of saws. The machine consists of two radial saw that can work together and cut both end of pugs simultaneously. Each cuts needs nearly 0.2 litter cooling water. This machine is designed to work with all types of cutting whee l (resinous - diamond - boron carbide) and various accessories and adaptations enable samples or core sections to be cut lengthways. These include cradles or devices for holding the samples configurations using two wheels which allow parallel-sided sections of continuous length to be cut in a single operation. The machine is fitted with a safety cut-out switch which can be reset, or rewound s hould there be no power, as well as a gradual starting device. When the cover is open this safety switch open the electric current and the machine don’t work. The use of passivated water is strongly recommended to avoid corrosion.
Experiment operation:The machine can work in both manual and automatic mode. By setting two lever taps on the body of machine, three situations are achieved. The lever taps allow the wheel (saw) to advance or return. ·
Quick back mode: in this mode the saws go back quickly and positioned at the start point. This mode can be achieved by setting both taps down.
·
Stop manual: in this mode user should handle the position of saws for trimming the plug manually and can be achieved by setting top tap to up and bottom tap to dawn
·
Automatic feed: in this situation samples are trimmed automatically by the machine. The rotational speed of the saws can be adjusted by the “Movement regulator” beside the lever taps.
Manual mode:Steps for operating in manual mode are as follows: ·
Press the start bottom
·
Set the taps to " Quick back " position, at the end of the race, the lever is independent of jack,
·
Set the taps to the "Manual stop" position. 10
·
Adjust the direction of water line on saw and sample
·
Check water tanks and fill them if they are empty
·
Start the water pump and check the direction of water and check the flow
·
Close the protective housing of machine
·
By moving the saws to front start trimming of the sample
·
Press the Start button
·
Press the « Stop » button
·
Unclamp the core sample
Automatic feed (optional):·
Steps for operating in automatic feed mode are as follows:
·
Press the start bottom
·
Set the taps to the " Automatic feed " position
·
Adjust the direction of water line on saw and sample
·
Check water tanks and fill them if they are empty
·
Start the water pump and check the direction of water and check the flow
·
Close the protective housing of machine
·
Gradually open the movement regulator until the required feed rate is obtained.
·
At the end of the cut, turn the taps to the "Rapid return” position.
·
Press the « Stop » button
·
Unclamp the core sample
Maintenance:Apart from keeping the machine properly clean, no specific maintenance is required. Make sure that any sediment or waste matter is removed from the tank before starting. Change the fluid according to the frequency of use and its deterioration over time (shelf life).
Tools:·
2 Pin wrench (50 mm)
·
1 Allen key set
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Figure-4:- Trimmed Core plug Sample
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EXPERIMENT NO. 3
Aim/ Objective:- To Cleaning of core sample in Soxhletion Extraction Unit. Apparatus Used:- Heater, Soxhletion Unit & Rubber pipes Chemical Used:- Methanol Liquid Cleaning of core sample After preparing the core plugs samples, the core samples must be cleaned of residual fluids and thoroughly dried.
Method of Soxhlet Extraction:A Soxhlet extraction apparatus is the most common method for cleaning sample, and is routinely used by most laboratories. As shown in Fig. 3, Methanol is brought into a slow boil in a Pyrex flask, its vapors move upwards and the core becomes engulfed in the methanol vapors (at approximately 65° C). Eventually the amount of water within the core sample in the thimble will be vaporized. The methanol and water vapors enter the inner chamber of the condenser; the cold water circulating around the inner chamber condenses both vapors to immiscible liquids. Recondensed methanol together with liquid water falls from the base of the condenser onto the core sample in the thimble; the methanol soaks the core sample and dissolves any oil with which it conic into contact. When the liquid level within the Soxhlet tube reaches the top of the siphon tube arrangement, the liquids within the Soxhlet tube are automat ically emptied by a siphon effect and flow into the boiling flask. The methanol is then ready to start another cycle. A complete extraction may take several days to several weeks in the case of low API gravity crude or presence of heavy residual hydrocarbon deposit within the core. Low permeability rock may also require a long extraction time
Parts of Soxhlet Unit:1: Stirrer bar/anti-bumping granules 2: Still pot (extraction pot) - still pot should not be overfilled and the volume of solvent in the
still pot should be 3 to 4 times the volume of the soxhlet chamber. 3: Distillation path
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4: Soxhlet Thimble 5: Extraction solid (residue solid) 6: Syphon arm inlet 7: Syphon arm outlet 8: Reduction adapter 9: Condenser 10: Cooling water in 11: Cooling water out
Figure- 5:- Parts of Soxhlet Extraction Unit. 14
Figure- 6:- The sample is placed in the thimble. Results Weight of core sample before experiment= x gms Weight of core sample after experiment= y gms Net Weight change_(x-y) gms or ----% Fluid Saturation =
----%
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EXPERIMENT NO. 4 Aim / Objective:- To find the Porosity of given core sample using Helium Porosimeter. Apparatus Used:- Porosity meter, Steel Billets, Helium Gas Cylinder & Software loaded computer.
Theory:From the viewpoint of petroleum engineers one of the most important property of a reservoir rock is porosity. Porosity is a measure of storage capacity of a reservoir. It is defined as the ratio of the pore volume to bulk volume, and it may be expressed as either a percent or a fraction, Ø= Pore Volume / Bulk Volume= Bulk Volume- G rain Volume/ Bulk Volume Two types o f porosity are total or absolute porosity and effective porosity . Total porosity is the ratio of all the pore spaces in a rock to the bulk volume of the rock while the effective porosity Ø e is the ratio of interconnected void spaces to the bulk volume. Thus, only the effective porosity contains fluids that can be produced from wells. For granular materials such as sandstone, the effective porosity may approach the total porosity, however, for shale and for highly cemented or vugular rocks such as some limestone, large variations may exist between effective and total poros ity. Porosity may be classified according to its origin as either primary or secondary. Primary or original porosity developed during deposition of the sediment. Secondary porosity is caused by some geologic process subsequent to for mation of the deposit. These c hanges in the original pore spaces may be created by ground stresses, water movement, or various types of geological activities after the original sediments were deposited. Fracturing or formation of solution cavities often will increase the original porosity of the rock.
Figure- 7:- Cubic packing (a), rhombohedral (b), cubic packing with two grain sizes (c), and Typical sand with irregular grain shape (d).
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Porosity measurement on core plugs:The porosity of reservoir rock may be determined by using core analysis, well logging technique or well testing. The question of which source of porosity data is more reliable can not be answered without reference to a specific interpretation problem. These techniques can all give correct porosity values under favorable conditions. The porosity determined from core analysis has the advantage that no assumption needs to be made as to mineral
composition, borehole effects, etc. However, since the volume of the core is less than the rock volume which is investigated by a logging device, porosity values derived from logs are frequently more accurate in the case of heterogeneous reservoirs. From the definition of porosity, it is evident that the porosity of a sample of porous material can be determined by measuring any two of the three quantities: bulk volume , pore volume or grain volume from core plugs (Fig. 6).
Figure 8:- Representation of the different volumes in a plug
i) Bulk volume:Although the bulk volume may be computed from measurements of the dimensions of a uniformly shaped sample, the usual procedure utilizes the observation of the volume of fluid displaced by the sample. The fluid displaced by a sample can be observed either volumetrically or grav imetrically. In either procedure it is necessary to prevent the fluid penetration into the pore space of the rock. This can be accomplished by: (1) Coating the sample with paraffin or a similar substance, (2) Saturating the core with the fluid into which it is to be immersed, or (3) Using mercury. Gravimetric determinations of bulk volume can be accomplished by observing the loss in the weight of the sample when immersed in a fluid or by change in weight of a pycnometer with and without the core sample.
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ii) Pore volume:All the methods measuring pore volume yield effective porosity. The methods are based on either the extraction of a fluid from the rock or the introduct ion of a fluid into the pore spaces of the rock. One of the commonly used methods is the helium technique, which employs Boyle's law. The helium gas in the reference cell isothermally expands into a sample cell.
After expansion, the resultant equilibrium pressure is measured. The Helium Porosimeter apparatus is shown schematically in (Fig.- 7).
Figure-9:- Helium Porosimeter apparatus is shown schematically
Helium has the following advantages over other gases: (1) Its small molecules rapidly penetrate into small pores. (2) It is an inert gas and does not adsorb on rock surfaces (air may do), (3) It can be an ideal gas (i.e., z = 1.0) for pressures and temperatures usually used in the test, (4) It has a high diffusivity so affords a useful mean for determining porosity of low permeability rocks.
Specifications:Working Pressure
90- 110 psi
Working temperature
Ambient 25° - 40°C
Gas
Helium
Connections
1/8" Swagelok type
Transducers
Range 16 bar (230 psi)
Power supply
1 Phase 220 VAC +/- VAC. Frequency 50 Hz.
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Installation:Connect the Console to:
Suitable Helium facility, rating up to 100 psi approximately
To the matrix cup.
With Optional PC interface :
Plug the communication cable to the Pc and the consol
Plug the console to the power supply
Switch on the console and the PC
Start the PC and run application
Check the there is no communication error between the PC and the Console
Calculation The ratio of Pore volume to the bulk volume is Porosity Porosity = (Pore Volume) / (Bulk Volume……………………….1 For Sharp cylinders, the bulk volume can be determined from geometrical measurement. The matrix cup can accommodate irregular core sample. In this case the bulk volume must be determined from mercury immersion for instance. Pore volume and grain volume can be determined as follows Core Samples- any shape. Unconsolidated acceptable Pore volume- from relation 2 Grain volume- directly Porosity- from the relation 3 Pore volume = Bulk volume – Grain volume………………….2 Porosity = (Bulk volume – Grain volume) / Bulk volume……………………3 Boyle- Mariotte’s law is used to determine grain and Pore volume from the expansion of a known mass of helium into a matrix cup. (Pref*Vref)/Tref = (Pexp*Vexp)/Texp………………… Boyle- Mariotte’s law Where:Pref = Reference Pres sure (initial pres sure) Vref = Reference volume (initial volume) Tref = Re ference absolute temperature (initial temperature) Pexp = Expended Pressure (final pressure) Vexp = Expended Volume (final volume) Texp = Expended Absolute temperature (final temperature) 19
The reference cell is pressured to 100 psi. Vref = Volume of the reference cell and associated piping volume. At a given moment, the valve H- V02 is opened “Expand” and then the gas expends into the matrix cup containing the sample to analyze. We assume that the temperature remains constant during a series of measurements: Texp = Tref to simplify the boyle- mariotte’s law. The gas expends in the volume Vref and the volume of the matrix cup, reduced by the volume of the solid (Vgrain):Vexp = Vref + (Vmatrix – Vgrain)…………………..a It comesPref×Vref = Pexp*(Vref + Vmatrix – Vgrain)………….b In the matrix cup, the gas volume gather s the volume sur ro unding the core (also named Vdead) and the Por e volume: Pr ef *Vref = Pex p*(Vdead+Vpor e) …………..c Fr om relation c we get Vpore = (Pref/Pex p)*(Vref - Bdead)…………….d Relation a can be wr itten as Vgrain = Vref + Vmatrix - Vexp ……………………….e Replacing Vexp from Boyle mariotte 's law, it comes Vgrain = (Vmatr ix + Vref). (Pref/Pexp)*Vref …………….f Pref and Pexp measured with the Porosimeter. Vref, and Vmatrix and Vdead are determined using the calibration method provide with the machine.
Procedure Initial pressure setting To set 100 psi accurately:
Proceed to the following instructions only after a successful tightness test
Switch on the console
Don’t connect the matrix cup
Wait for half an hour to get transducer stability
Reset the control valve on the console
Connect the console to the helium facility
Set at 120-150 psi at the facility 20
Check that HV01 is open and HV02 is switched to “Exaust”
Adjust the control valve until getting 100 psi sharp on the application display
In case pressure is too high a. Close HV01 b. Switch HV02 to expand for 1 second c. Turn the control valve anticlockwise d. Open HV01 e. Adjust the control valve to get 100 psi sharp
Watch 2- 3 minutes to check that the pressure is OK
Operation A measurement campaign must follow a calibration sequence. The calibration procedure exploits the relation f in the reverse way. We have:a = - Pref*Vref x = 1/ Pexp b = Vmatrix + Vref We get a linear relation: Vgrain = ax + b where a and b are unknown and x is determined from the expended pressure measured with the apparatus. We can generate calibrated grain volumes with reference billits introduced sequentially in the matrix cup. By running (a minimum of) 2 measures with calibrated billets (Vgrain), we can determine a and b; fc pyc it fc cecy ph fc c pdict d yp cycec si cg1/P. for better accuracy it is recommended to run at least 4 experiments. Shut of Procedure
Bleed off the pressure of Helium at the gas supply
Close HV01
Switch HV02 to exhaust
Set back the billets in the solid case
Result The Porosity of given core Sample is…… X %………….
Maintenance Leak Test 1. Switch on the console for 1 hour minimum to get stability 2. Close all the electro valves via APPLILAB interface 3. Set an upstream helium pressure of 120 psi from the facility 21
4. Open the manual valve at the console 5. Open the electro valves EV1 6. Adjust the pressure control valve to get exactly 100 psi at the pressure display 7. Close the electro valve EV1 8. Run history to log the pressure and the temperature 9. Wait for half an hour. The pressure reading should be higher than 99 psi for a constant temperature. If the Pressure has dropped
10. Switch off the console 11. Unplug the Console from the power supply 12. Proceed to leak detection with an helium detector 13. Fix the leaks 14. Proceed to an new leak test (step 1 to 9) until getting satisfaction.
Figure- 10:- Setup of Porosimeter.
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EXPERIMENT NO. 5 Aim/Objective: - To find the Liquid Permeability of the given core sample using Liquid Permeameter.
Apparatus Used: - Liquid Permeameter, Brine Saturated Core Plug and 2-Nitrogen Cylinder.
Theory:Permeability is a property of a porous medium which shows the ability of porous media to transmit fluids. The reciprocal of permeability represents the viscous resistivity. The effective Permeability of a porous medium is a measure of the rock conductivity to a particular phase of a multiphase fluid system residing within the porous medium, where the saturation of each phase is specified. Relat ive permeability is the ratio of the effective permeability of a particular fluid phase to some arbitrary reference permeability (i.e. absolute permeability). Permeability has the unit o f m2 in SI system or Darcy in field unit with a conversion factor of 1D ≡ 0.986923×10 -12 m2 . Note that a rock sample has a permeability of one meter squared when it permits 1 m3 /s of fluid of 1 Pa.s viscosity through an area of 1 m 2 under a pressure gradient of 1 Pa/m. Per meability' can be calculated by Darcy's Law, which for liquids under steady state conditions of viscous or laminar flow may be ex pressed as:-
K =
QµL . AΔP
.
Where, K = liquid permeability (Darcies or md) µ = viscosity of saturating liquid (Cp) Q = liquid flow rate (ml/s)
L = length of right cylinder porous medium (cm) A = cross sectional area of cylinder (cm2 ) P = pressure differential across cylinder (Atm) Calculation
Core dimension: length (cm) is written at column C and D f or each sample. Area (cm2 ) is obtained from diameter written at column D for each sample.
Viscosity default value for test brine is set to 1. Read the temperature and adjust
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Viscosity by reading Handbook of Chemistry.
Flow rate: Q (ml/s) is calculated time (minutes and seconds) at column F and G to fill the flask volume (column E).
Diff erential pressure ΔP (psi) is obtained from direct reading at the console of upstream pressure P1 because outlet pressure is atmospheric : ΔP = P1 - P2 (atm) = P1 (atm)
The unit conversion (psi to Atm) is automatically made in XLS report.
Figure- 11:- Injection System 24
Procedure:1. Connect to main supply and Power up the instrument at main switch on the rear panel. The pressure transducers require an “warm up” period of about one hour before use. 2. Switch the Source value ON / OFF to OFF position. 3. Ensure that regulators are fully turned anticlockwise initially. 4. Connect two regulated nitrogen supply at the appropriate ports on the rear of the instrument, i.e. confining pressure supply at valve PRESSURE / VENT (1/8" OD) and core nitrogen supply at valve on/off (1/8" OD). 5. Initialize the system by filling the dead volume with brine by proceeding without core in place at first step (confining pressure should NOT be applied) 6. Load the core holder. Different core holders are available for sample diameter of 1", 1.5", 30 mm etc. 7. Regulate confining pressure supply to desired value with out exceeding 400 psi. Regulate core nitrogen supply without exceeding 100 psi. 8. Turn confining valve PRESSURE / VENT to PRESSURE. Gas at desired pressure is now applied to the core holder sleeve. This pressure is now displayed on confining pressure gauge.
MEASUREMENT OF CONSOLIDATED CORES SAMPLE 9. Sample Name/No : 10. Length, L : 11. Diameter, d : 12. Liquid Viscosity; : ΔP (psi)
Duration, Δt (sec)
Volume of Liquid collected (ml)
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Flow rate (cc/sec)
Calculation Sheet ΔP/L
q/A
K
Result:The Liquid Permeability of Given Core Sample is ………………. md.
Maintenance:1. Leak test:Before starting the unit, a leak test must be performed. PCV cannot be tested because a built-in vent releases the pressure in absence of flow. For this reason, disconnect the 2 Pressure control valve and plug the downstream the PCV. 2. Instrument calibration:For optimum accuracy, pressure transmitter must be calibrated on a regular basis.
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EXPERIMENT NO. 6 Aim/ Objective: - To find the Permeability of given core sample using Gas Permeameter. Apparatus Used: - Nitrogen Gas, Permeameter. Introduction:The Gas per m is a r esear c h quality instr ument but it can be used for r o utine core analysis when rapid sam ple tur naround a nd thr oughput is desira ble. A mass flow meter of range 0-500 cc/min with a 0- 29 psi relative pressure transmitter ar e used to sense gas flow a nd pr ess ur e drop acr oss the sam ple and ther efore provides an accurate determination of permeability, when the transmitters have been cor re ctly calibrated.
General specification
Max. pressure 100 psig (line pressure)
400 psig (confining)
Operating temperature Room temperature 18- 28 °C
DP transducer range 0 – 8 psid
Flow range (low)- 0 – 20 cc/min
(high) 0 – 2,000 cc/min
Connection 1/4” and 1/8” SWAGELOK type
Sample size Dia (according to model) 30 mm 1” 1”1/2
Length 1 to 3”
Facility required
Power supply 240 - VAC 1 phase + ground 50 Hz / 60 Hz 200 W
Nitrogen supply adjustable up to- 100 psig (line pressure) 400 psig (confining)
Miscellaneous accessories required
Gas operated pressure calibrator (0- 100 psig) with small increments.
Soap film flow meters (eg.G.C. accessory) or reference flow meter.
To fit 0 – 20 cc/min and 0 – 2,000 cc/min ranges
Stop watch
Caliper
Thermometer- optional
Barometer 27
Theory, Calculation and interpretation of steady state results Theory:Dar c y's law is used for the calculation of permea bility, which under steady state conditions f or viscous or laminar flow is: k = µQL/ AΔP ... (1) Wher e: k = liquid per mea bility (D standing f or Darcies) µ = viscosity of saturating liquid (Cp) Q = liquid flow rate (ml/s) L = Length of r ight cylinder porous medium (cm) A = cr oss sectional area of cylinder (cm2 ) The expressio n for deter mining the permeability of porous medium to gas is of different from to that of liquid because of the fact that gas is compressible whereas liquid is not. Gas flows towards the downstream end of core sample, its pressure decrease, the gas expands and so its velocity will increase. The Darcy equation for ideal horizontal laminar flow of gas under steady state isothermal condition is given by: k gas = [2µZT (Pb) L (Qb)] / [A(Tb) (P 1 2 – P2 2 )]…….(2) Where as:k gas = permeability to gas (mD) µ = gas viscosity (Cp) Z = mean gas compressibility factor T = mean temperature of flowing gas Pb = base or atmospheric pressure (absolute Atm) L = length of sample (cm) Qb = atmospheric gas flow rate (cm/s) at base pressure Pb A = cross sectional area of cylinder (cm2 ) Tb = base temperature (ambient) P1 , P2 = upstream and downstream absolute pressure respectively. Now, if the ba se temperature equals the mean temperat ure of the flowing gas a nd Z is taken as the unity, which is approximately true for nitrogen under typical operating ambient 28
conditions, and since core pressure drop p = P 1 – P2 ;and core mean pressure Pm=(P1 + P 2 )/2 then the equation (2) can be reduced to the less unwieldy expression: k gas = [(Qb) µL (Pb)] / [AΔP (Pm)]…..(3) Where as: µ = gas viscosity (Cp) Qb = atmospheric gas flow rate (cm/s) Pb = base or atmospheric pressure (absolute Atm) ΔP = differentia l pressure (Atm) Pm = mean core gas pressure (Atm) L = length of sample (cm) A = cross sectional area of cylinder (cm2 ) This equation is therefore used to calculate core permeability to nitrogen, under laminar flow conditions.
Calculation:
Viscosity for nitrogen is calculated automatically from Sutherland’s formula in the XLS report, depending on temperature during the test. µ = µo * (a/b) * [(T / To ) raised to power 3/2]
Flow rate: Q (ml/s) can be obtained from direct reading at the console.
Core dimension: length (cm) and area (cm2 ) are obtained form measurements made on core plug and reported on the XLS report tab “INFO” respectively at column C and D for each sample.
Ambient pressure: Pb (atm) can be obtained from measurement of the atmospheric pressure o n a barometer (ps i) a nd reported on XLS report tab “CONTROL” at line 5, column B.
Differential pressure DP (psid) is the difference between core upstream P 1 and downstream P2 pressure across the core. ΔP = P1 -P 2 (atm)
For ΔP less than 8 psid, differential pressure is given directly from the DP transducer suitably corrected for any zero shifts. Unit conversion (psi
Atm) is automatically made in the XLS
report. If no back pressure is used, then: P 1 = ΔP (psid) / 14.695949 + Pb (atm) and P2 = Pb (atm), this takes advantage that DP reading is more accurate than P1 = reading (3 decimals instead of 2). 29
If back pressure is used, then P 1 = [P1 (psig)/140695949] + Pb(atm) and P2 = [P1 (psig) – ΔP (psid)]/ 14.695949 + Pb(atm).
Core mean pressure Pm is found from Pm = (P 1 + P2 ) /2 (atm) where P1 and P 2 are calculated as in stage above.
Interpretation of results:Klikenberg (1) noted that gas permeability decreased as the mean gas pressure in cores increased, and found that the gas permeability of a core was always higher than its permeability to a single saturating inert liquid. If the gas permeabilities obtained at different mean core pressures are plotted against reciprocal mean pressure (1/Pm), a straight line should be able to be drawn through the points. Extrapolation of this line to infinite mean pressure (i.e. zero rec iprocal pressure) intersects the gad permeability axis. The intersections points correspond to the liquid permeability and may be found from: K L = Kg/ [1+ (b/ Pm)]
WhereK L = theoretical liquid permeability b = Klikenberg correction factor. The slope of the line is given by bK L The factor b is different for different gases and decreases as the liquid permeability increases.
Sample operation:Sample selection The core sample used in the Gas perm must be right cylinder with end faces perpendicular to the core axis with a diameter close to 25 (1”) or 38 mm (1½") according to version in use. Core with uneven or irregular e nds or with diameter significantly less than nominal might cause the sleeve to rupture when confining pressure is applied.
Core holder selection Check that the sample is of suitable diameter 1” or 1.5" according to core holder installed. To change the core holder, release the overburden pressure, then disconnect the confining SS tubing from the core holder. Disconnect and remove the inlet and outlet flexible tubing. Installing core holder is reverse procedure.
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Removing a core sample To remove the core sa mple, firstly ens ure that the flow system and confining system has been depressurised: switch the valve ON OFF to OFF position, switch the valve DP ON / DP OFF to OFF. Release the confining pressure by switching PRESSURE / VENT to VENT. Slacken the adjustment screw slightly turning the screw anti-clockwise about a quarter turn, and pull back the SS connection tube from the core face. Pull on the outer knurled ring then rotate a quarter turn until the end platen component is freed. The quick release end should be able to be easily removed. If the core does not come on the bottom platen, help by pushing the top platen. Be careful not to use too much force initially – just sufficie nt to free the core from the sleeve.
Loading a core sample
Place the core in the core holder and push it with the quick release end plug until it butts against the adjusting platen.
Replace the quick release en plate n by lining up the male clover leaf component with the corresponding female component.
Now, push the inner knurled ring forward a nd rotate the r ing clockwise until it locates
in position If the length of the sample is longer than the previous sample, you may encounter resistance when inserting the end platen. Turn the adjusting screw anticlockwise, and pull back on the SS junction tube until the quick release en platen ca be easily inserted. The adjusting screw should now be turned clockwise until the other end platen contact the core face. This is all that is required to ensure a pressure seal. Never attempt to over tighten the adjustment screw. When properly engaged, the quick release end neither this platen nor the adjustable end platen will be able to be moved. In case the platen can be moved, dismount the adjusting platen and insert the bronze spacer provided with the core holder. Note: the adjusting screw thread should be totally e ngaged in the bod y. I f is not the case, the sample is too long and not acceptable for test in the Gas perm. Do not attempt to finally, switch the valve PRESSURE / VENT to PRESSURE to set the confining pressure.
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Instrument operation procedures:Initial procedure
Connect to main supply and power up the instr ument at main switch o n the rear p anel. The pressure transducers require a “warm up” period of about one hour before use.
Switch the source valve ON / OFF to OFF position.
Ensure that regulators are fully turned anticlockwise initially.
Connect two regulated nitrogen supply to the appropriate ports on the rear of the instrument, i.e. confining pressure s upply at valve PRESSURE / VENT (1/8" O D) and core nitrogen supply at valve ON / OFF (1/4 “ OD). 100 psig connection for flowing gas. Fitting ¼ " OD.
Set the valve to OFF position before connection.
Load the core holder. Different core holders are available for sample dia. of 1”, 1 ½”, 30 mm etc.
Regulate confining pressure nitrogen supply to desired value registered on supply cylinder gauge. Regulate core nitrogen supply using cylinder regulator to just above desired maximum test pressure (without exceeding 220 psi).
Turn confining valve PRESSURE / VENT to PRESSURE. Nitrogen at desired pressure is now applied to the core holder s leeve. This pressure is now displayed on confining pressure gauge.
Result The Gas Permeability of given Core Sample is…………………m Darcy.
Maintenance Leak test Before starting the unit, a leak test must be performed. PCV cannot be tested beca use a builtin vent releases the pressure in absence of flow. For this reason, disconnect the 2 Pressure Control Valves and plug the unit downstream the PCV. When the second stage leak test is OK rotate the switch valves to check all sections. In the above illustration, we display a satisfactory pressure ramp (the scales are magnified to check the leak rate.
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EXPERIMENT NO. 7 Aim/ Objective: - To find out Resistivity, formation factor and cementation exponent of given core sample in (EPSA) Resistivity Meter. Apparatus Used: - Resistivity Meter, Compressor or Air Cylinder
Introduction Cor e Resistivity measurements, together with porosity and resistivity of connate water is used for calculation of water saturation, in porous volume of reservoirs; consequently hydrocarbon content can be calculated by dif ference. This information is essential for proper management of reservoir .
Machine Description: The system includes:
An atmospheric Electrical Core Holder
An ambient Brine Resistivity cell
A RFL meter (Fluke make)
The apparatus consists of:
1. A plastic cover which contains the electrodes and the sample during measurement. 2. Two electrodes, one fixed, one movable to enable measurements on cores of size 2" to 3". 3. A piston and integral valve to facilitate the movement and ensure repeatable contact pressure on the electrodes. 4. Connectors and cables for connection to the RFL measuring device. 5. A special plug for connection trimming (for 1" and 1½" diameter samples)
Figure-12:- Illustration of core sample loading 33
Figure 13: Illustration of system under locked pin and tighten the knob
Theory and Calculation 1. Phenomenon involved
In brine, the electrical conduction r e lies on the tr ansport of ions, pr edominantly sodium, Na f - , and chloride, (1- , ions. The core samples saturated or partially saturated with br ine are conductive thr ough the connate brine
In rock with open, well connected pore paths filled with br ine, ion flow occurs easily and resistivity (Rw) is low.
Rocks with sinuous, constricted pore paths hinder ion transport and have higher resistivity.
2. Resistivity (Ro) Ro = R . (A/L) = (V /I).(A/L)
Where:R is the core resistance (Ohm or n) A is the core cross section (m2 ) L is the core length (m) V is the potential (Volt) between the 2 electrodes I is the current (Amp) going through the core. 3.
Formation Factor (Fr) Fr = Ro/Rw
Where: Ro is the core resistivity (Ohm. m or n. m) at 100% brine saturation and Rw is the brine resistivity (Ohm. m or n. m)
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4.
Cementation Exponent (m)
Fr = a
-m
Where: a is the Archie's coefficient (unit less) is the core porosity (unit less) m is the cementation exponent (unit less)
For a tank of water, Ro = Rw. Therefore Fr = 1. If porosity is zero, Fr is 0 and both a and m can have any value. However, for real rocks, both a and m vary with grain size, sorting, and rock texture. The normal range of a is.5 to l.5 and f or mis 1.7·1:0 about 3.2. Finally, “a” is commonly taken equal to 1 and ma can be expressed as:
m = -[In(Fr)/Ln()]
5.De termination
of Archie constant a
Most of time Archie constant is taken as equal to one. When you have samples of various porosity from the same field formation, it is possible to determine accur a tely the value of a. For each sample, measure Fr = Ro/Rw and then plot the Fr versus porosity obtained from he same field formation.
Using XLS trend facility (add trend line/Power/ display equation) fit this data wit h a curve of type Fr = a ( raised to power -m)
6.Resistivity
Index (Ir), Saturation
Ir = Rt/Ro = Sw raised to power -n
Where Rt is the core resistivity (ohm. m or n. m) Ro is the core resistivity (ohm. m or n. m) at 100% brine saturation Sw is the core saturation (unit less) n is the saturation exponent (unit less)
And then, Saturation Exponent can be e x pressed as: n == - [Ln (lr) / Ln (Sw)] 35
Procedure
Sample loading 1.
Ensure the piston is fully retracted. Wet 2 pads with test brine.
2.
Stick them on the electrode plates respectively.
3.
Take a core sample from the brine and roll it once over paper towel to remove surface brine.
4.
Lie and balance the core sample on the seat.
5.
Rotate the piston switch to actuate the cylinder; this will cause the core sample to be firmly held between the 2 pads.
6.
Topple the e lectrode set on the sample and dose the lid over the sample to prevent evaporation of the liquid from the sample.
7.
Close-up for correct loading.
Adjustment for small length sample
1. For small length samples, lift one of the cradles and insert back in order to reduce the supports distance. 2. If the pins are not o n the 'sam ple because the sam ple is too short; then we can use the 2 leads pattern.
Sample unloading
After measurement, retract the cylinder by rotating the valve command in the appropriate dir ection. Open the lid and the electrode. In case that the measure series is completed or in case that the next measurement concer ns dif ferent brine, caref ully dr y the electrode a nd oper ate with new wet pads.
Dip Cell
Descr iption: The dip cell consists of a probe with electrodes em bedded. It must be completed with a ther mometer to di p c lose to the Di p Cell in a beaker .
Connection: Plug the connector to the RCL mete r in r es pect of the r ed dot orientation (on to p of the connector).
Calibration and measur e
Result The value of Ar chie's constant is………………………. . 36
Maintenance As with most systems operated with br ines the most important consideration is ensuring the brine doesn't corrode the metals or crystallize in the apparatus. Therefore all the cells which have been in contact with brine should be flushed thoroughly w ith d istilled water and then dried with a cloth after use.
EPSA
If the electrode plate is partially covered with o ld pad deposit then remove the pad and rub it with new wet pad. Dip cellIf the measure is not possible, check the junction cable . For this purpose, disconnect the cable from the RCL meter . Now, check each of the 4 leads. Repair or order another cable.
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EXPERIMENT NO. 8 (Under Development) Aim / Objective:These experiments will be carried out with the given - Graphs so as to solve particular numerical problems related to specific objectives on various topics given below:1. Rese rvoir Modeling & Simulation 2. Basic Reservoir Engineering 3. Production Engineering 4. Drilling Engineering
5. Well Stimulation
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