1. PROCESS PROCESS DESCRIP DESCRIPTION TION AND CONTROL CONTROL 1.1 Process Description Description A mixture of oil, gas and water is produced through each well head by virtue of the well head natural pressure and its flow rate is controlled via a choke valve which a multi-position is throttling valve located on the surface. Choke valve is motor operated and its opening is based on production targets defined for the well and on results of well testing. Pressure of this fluid is monitored at upstream of choke valve by a pressure transmitter. Well head production line is oined with a production and a test manifold. !n test manifold, only one well head flow is aligned in order to determine individual phase flow rates, pressure, temperature and density. After that it is connected with manifold line and then with trunk line. "!PP# is provided on each trunk line. With the passage of time, natural pressure of well will be depleted. An electrical submersible pump $%#P& will then be installed in place of the ##'( in the each well to make the re)uired pressure and pump the mixture out. 1.2 Integrated Control Control and Safety Safety Syste *.+.* !C## descript description ion he ishr ishrif if Cent Central ral Proc Proces essin sing g acil acility ity has has proce process ss cont contro roll syste system m $PC#& $PC#& and and safe safety ty instrumented instrumented system $#!#& combined combined for better communication communication between the two and termed as !ntegrated Control and #afety #ystem $!C##&. or this proect, !C## constitutes of the following systems. •
'C#
•
%#'
•
P/C
•
0'#
•
P
•
%#P
•
#
his integrated 'C#, %#', 10, %#P, # and P/Cs are connected through a control and communication networks for ease of production control and maintenance. 2emote ac)uisition of well pad data and process variables are available in the central control build buildin ing g loca locate ted d in the CP CP. he he !C## !C## is of dist distrib ribut uted ed topo topolo logy gy and and the syste systems ms are are connec connected ted throug through h redund redundant ant data data commun communica ication tion networ network k connec connecting ting severa severall 3nodes 3nodes44 located in field in dedicated 3#atellite !nstrument "ouses4 $#!"& for each well pad. he 56 no$s& of #!" for their respective Well Pad are given below in table 7.+.*.
*.+.+ Well Pad Control %ach well pad has its dedicated #!" for control and monitoring the key parameters and production as stated in table 7.+.*. he #!" 8 6,9,:,; and *5 have similar architecture and they communicate through a redundant fiber optic link to the telecom room in CP control room. Table 3.2.1 – SIH detail for each Well Pad
Sr. !
SI" !
#ell Pad !
*
;75-#!"-*56
Well Pad 56
+
;75-#!"-*59
Well Pad 59
7
;75-#!"-*5:
Well Pad 5:
<
;75-#!"-*5;
Well Pad 5;
6
;75-#!"-**5
Well Pad *5
*.+.7 #atellite !nstrument "ouse As stated above in table 7.+.*, every well pad has a dedicated #!" for monitoring and control. !t houses all the component of the !C## as per re)uirement. A network cabinet is deployed where fiber optic to %thernet convertors are installed. Also, there are network switches which are used to route the communication through redundant channels. his cabinet is used as the point for communication between #!" and CP control room. #eparate cabinets are present for each of the !C## components. hey are mainly P'P, 0'#, 'C#, %#', P# and an engineering work station to facilitate configuration and engineering in all the 56 no$s& #!". •
'C#
he 'C# provides process control and monitoring for the plant such as basic regulatory and se)uential control, non-safety related interlocks, process monitoring, alarm management, data archiving, trending, reporting etc. !t is to be noted that the 'C# controller hardware and !=> are distributed geographically with the modulari?ed plant philosophy. he 'C# architecture, being the backbone of the !C##, is integrated with all other components of !C##. •
%#'
he %#' is a dedicated control system responsible for the safe and controlled shutdown in wake of any emergency , process upset or planned shutdown. he %#' operation is separate from the 'C# and does not take part in the regulatory control of the process plant. he %#' consoles are also present with hardwired push buttons for initiating shutdown. he logic of the shutdown is derived from the cause and effect drawings of the process plant.
•
ire and 0as 'etection #ystem
he 0'# is responsible for early warning of any leak or fire in the process facility. !t is also a dedicated system which is separate from any other control system of the !C##. !t communicates with the main CP through a dedicated optical fiber link. here a number of detectors installed in the field and the buildings for the early warning of the same. •
ulti Phase etering #ystem
he P# is used for multiphase flow metering of the process medium from the well and is a packaged unit. he P# panel located in each #!" is used for flow computing and communicates to the CP control room to the dedicated engineering server for flow computation. •
Power 'istribution Panel
he power distribution panel is located in each of the #!" for the !C## components. !ts e)uipped with the redundant power supplies along with the circuit breakers. •
(ariable #peed 'rive
here is also a variable speed drive panel which is used to vary the speed of any electrically driven pumps operated from their respective #!". !n #!" 5:, other than the standard configuration, 5+ no$s& of P/C are deployed, one for instrument air and other for test water inection. hey communicate to 'C# via a redundant fiber optic network from field. he %#' and 'C# also communicate to the main CC as part of the system architecture hence the motor start = stop and status is available as per the control philosophy. A W"CP is present in field which is used to control 5< no$s& of wells of each well pad and is communicated through hard wired signals to 'C# and %#' both. he typical configuration of the #!" is given in the figure below.
*.+.< ield Control Panel !n ield, a dedicated control panel known as W"CP is provided for ease of operation. %ach W"CP is able to control 5< no$s& of well heads. he W"CP drives the hydraulically actuated valves essential for well operation. he W"CP has indications and controls for the hydraulic valves, pumps and their status. All Wellhead Control Panels have the following functionality *. Pump discharge, CP header, usible loop, ###'(, ##'( and %@( pressure indication. +. All pumps of the well head can be put on local=remote=off through a selector switch located in the same W"CP. 7. 'edicated start and stop buttons are given for each pump of the wellhead. >ther than that the Wellhead Control Panel $W"CP& provides •
•
•
!ndividual well control $local control from the W"CP& he hydraulic power for all three valves of each of the < well head i.e. ###'(, ##'( and %)uali?ing valve and their hydraulic pressure indicated through pressure gauges located in the front of the W"CP !nformation and command switches for each well and for the hydraulic supply unit. or each well head, dedicated %#' push button along with the reset button is given with %#' status lamp. he 57 no$s& of the valves i.e. ###'(, ##'( and %@( can be opened and closed through the push buttons located in the front of the W"CP. heir opening and closing indication is shown through a dedicated lamp. he lamps turn green for open indication and are turned off for closed indication.
he W"CP is e)uipped with the "P and /P header for the hydraulic oil along with the accumulator. hey are e)uipped with the pressure transmitters for monitoring the pressure. he accumulator is also e)uipped with a level transmitter. he following settings apply to the hydraulic supply pressure to surface and subsurface safety valves. ###'( •
ax working pressure 6655-:555 psi
•
in working pressure 955 psi
•
'esign pressure *5555 psi
##'( •
ax working pressure 7555 psi
•
in working pressure *+55 psi
•
'esign pressure 9555 psi
1.$ E%ER&ENC' S"(TDO#N *.7.* %mergency #hutdown 'escription %mergency #hutdown #ystem $%#'& is designed to safely shut down all or part of the Well pad as the situation demands. he emergency shutdown of each well pad is fully detailed in documents •
%mergency #hutdown 'iagram
•
Cause and %ffect diagrams
he %#' functions at CP and well pads are interconnected. he %#' can also be initiated from the CP control room %#' hardwired console or from the individual W"CP panel by pressing the dedicated push button for each well head. he following paragraphs describe the general well pad shutdown. %ach system $production, test separation& is detailed in its respective book in this manual. he well pad %#' system is divided into three main %#' levels. *.7.+ %#' /evel 5 %#' /evel 5 is a very high level of shutdown and causes complete shutdown of the all well pads. Causes •
ain power supply down
•
anual activation of switch 555-55-%"#-55*-A
%ffects •
All well pads shutdown $56, 59, 5:, 5;, *5&
•
All well heads shutdown
•
Corrosion inhibitor pumps shutdown
•
#cale inhibitor pumps shutdown
•
Asphaltene inhibitor pumps shutdown
*.7.7 %#' /evel * %#' /evel * is a high level of shutdown and causes complete shutdown of the single well pad. Causes •
anual activation of switch 555-55-%"#-55<-A
•
Confirmed fire
•
Confirmed gas detection
%ffects •
All the well heads on single well pad will be shutdown.
*.7.< %#' /evel + %#' /evel + is a low level shutdown which will trip only one well head. Causes •
"and switch push button located on the W"CP
•
/P fusible plug
•
Well head pressure "igh "igh
•
Well head pressure /ow /ow
%ffects •
!ndividual well head will be shutdown
Bote
!t is important to remember that the ###'( will not be closed on this shutdown level.
