Process Control Philosophy Rev A

VIETSOVPETRO - VIETNAM

NAM RONG DOI MOIRC-4 Wellhead Platform

PROCESS CONTROL PHILOSOPHY

A 18.11.08 ISSUED FOR CLIENT'S COMMENTS RM VJ AMA

REV. DATE DESCRIPTION PRPD. CHKD. APPD.

TECHNICS OFFSHORE ENGINEERING PTE LTD,

SINGAPORE

Saipem Triune Engineering Pvt. Ltd., New Delhi

PROCESS CONTROL

PHILOSOPHY

DOCUMENT NUMBER REV.

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SHEET 1 of 45

TABLE OF CONTENTS

1 INTRODUCTION..4

1.1 OBJECTIVE...4

2 GENERAL DESCRIPTION 4

3 ABBREVIATIONS5

4 BRIEF PROCESS DESCRIPTIONS.....6

5 DESIGN BASIS.8

5.1 DESIGN FLOW RATES...8

5.2 OPERATING & DESIGN CONDITIONS9

5.3 COMPOSITION OF CRUDE OIL FEED....10

5.4 COMPOSITION OF GASLIFT GAS...11

5.5 CHARECTERISTICS OF PSEUDO COMPONENTS12

5.6 METEROROLOGICAL DATA...13

5.7 SIMULATION CASES...14

6 PROCESS SYSTEM CONTROL PHILOSOPHY21

6.1 FACILITIES TO CONTROL ...21

6.2 TYPES OF BASIC CONTROL ...22

6.3 BRIEF DESCRIPTION OF MAIN CONTROL SYSTEMS ...23

3.1 PROCESS CONTRO & MONITORING SYSTEM (PCS)..23

3.2 SAFETY & EMERGENCY SHUTDOWN SYSTEM (SSD)..25

6.3.3 FIRE & GAS DETECTION & FIRE FIGHTING (FGS)....26

6.3.4 REDUNDANT LOCAL AREA NETWORK (R-LAN)..27

6.3.5 SCADA.28

6.3.6 WELLHEAD CONTROL PANEL (WCP) .28 TECHNICS OFFSHORE

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7 OPERATION AND CONTROL OF PROCESS SYSTEMS...29

7.1 WELL FLOW LINES CONTROL..29

7.2 INLET MANIFOLD CONTROL31

7.3 TEST METERING STATION32

7.4 RISERS CONTROL32

7.5 PRODUCTION SEPERATOR V-40033

7.5.1 SEPARATOR LEVEL CONTROL.34

7.5.2 SEPARATOR PRESSURE CONTROL..35

7.5.3 CUSTODY FLOW METERS..36

7.5.4 SEPARATOR OTHER CONTROL.36

7.6 VENT SCRUBBER V-200..37

7.6.1 VENT SCRUBBER TEMPERATURE CONTROL37

7.6.2 VENT SCRUBBER LEVEL CONTROL 37

7.7 CLOSE DRAIN & OPEN DRAIN SYSTEM (V-300 & V-301)38

7.7.1 DRAIN TANKS TEMPERATURE CONTROL..39

7.7.2 DRAIN TANKS LEVEL CONTROL..39

7.8 GASLIFT DISTRIBUTION SYSTEM40

7.8.1 GASLIFT METERING STATION..40

7.8.2 GASLIFT GAS TO INDIVIDUAL WELL..41

7.8.3 GASLIFT FOR SLUG REMOVAL & FOR GAS DISPOSAL...42

7.9 CHEMICAL INJECTION SYSTEM..43

7.9.1 DEPRESSANT..43

7.9.2 DEMULSIFIER.44


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1.INTRODUCTION

1.1 OBJECTIVE

The purpose of this document is to define the main control functions for the process system. It

is intended that this document be used for the following.

Developing and/or reviewing P&IDs.

Guidance to control engineer in developing the instrument hardware requirements

In developing Operating Procedures, Operating Manuals, etc.

2.GENERAL DESCRIPTION

Well fluids from DRAGON Oilfield located in the Continental Shelf of South Vietnam, shell

be collected at RC4 Platform which is owned by VIETSOPETRO, a Joint venture of Vietnam

& Soviet.

The RC-4 Platform comprises of the following process facilities :

Collection of well fluid from various Wells: Wells number 01 to 09.

3 Injection Wells where Injection water is used.

Separation of Gas & liquid and transportation of gas & liquid to the Processing platforms RP-1, RP-2 & RP-3.

Gas Lift disposal to cold vent through Vent Scrubber.

Gaslift Distribution System.

Risers balcony where Gas & Liquid from other platforms RC-5 & RC-DM are also joining.

Risers for Gaslift from RP-3 platform and distributing to other platforms.


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3.ABBREVIATIONS

API American Petroleum InstituteAPS Platform Abandonment SignalAS Area Supervisory StationCCR Central Control RoomDCTS Data Collection and Transfer System DCU Data Collection UnitDTU Data Transfer UnitEDG Emergency Diesel GeneratorESD Emergency ShutdownF&G Fire and GasHV High VoltageHVAC Heating Ventilation and Air ConditioningLCP Local Control PanelLCS Local Control SystemMCC Motor Control CentreMCC Motor Control CentreP&ID Piping and Instrumentation diagramPA / GA Public Address / General Alarm SystemPCS Process Control SystemPGCS Power Generation Control SystemPLC Programmable Logic ControlPSD Process ShutdownPSMCS Power Supply Monitoring and Control SystemRB Riser Block / BalconySCADA Supervisory Control and Data AcquisitionSCSSV Surface Controlled Subsurface Safety ValveSWP Satellite Well PlatformUPS Un-interruptible Power SupplyUSD Unit ShutdownWCP Wellhead Control panelWS Work Station


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4.BRIEF PROCESS DESCRIPTION

The crude oil from all 9-production wells reaches to inlet manifold skid of RC-4 via their own

respective flow lines. The manifold skid is assigned for collection and distribution of well

product into individual process lines. It consists of blowdown valves and 4 headers as below.

a) Well production Collection Header

b) Testing Header for well testing and metering

c) Vent Header

d) Drain Header

Fluid from wellhead passes through a choke valve to control the flow towards production

header.

From production header, well fluid is routed to Inlet separator which is a two phase separator

or it is directly routed to remote processing platform RP-3 through sub sea pipeline by

bypassing the inlet separator.

Separated liquid/gas mixture from separator after level control valve is transported to RP-1 via

sub sea pipe line. The Pig Launcher is also provided at RC-4 platform on this line. Liquid/gas

mixture from platform RC-DM is also routed to RP-1 platform via RC-4 through RC-4

liquid/gas mixture line. There is a Pig receiver at RC-4 platform on the RC-DM liquid/gas

mixture line.

Test header after the Test Metering Station is also routed to separated liquid/gas mixture line

after Production Separator level control valve.

The Produced Gas from Production Separator after its pressure control valve is transported to

RP-3 platform through a common gas transferring line. There are two more similar facility


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platforms RC-5 & RC-DM at the same area whose gas production goes to RP-3 platform via

RC-4 platform through this common gas line to RP-3.

The Gaslift gas from processing platform RP-3 arrives at RC-4 platform via 16 Km long

pipeline. After reaching at RC-4 platform, it is divided into three lines for RC-4, RC-5 & RC-

DM platform use. 8 Gaslift line towards RC-4 is reduced to 4 and then goes to a metering

station. From metering station, gaslift gas is distributed to all 9-production wells through

gaslift distribution manifold by flow controller.

The discharge of all PSVs, BDVs from manifold, Production Separator & Gaslift distribution

system is routed to Vent Scrubber via vent header. The gaseous discharge form Vent Scrubber

is sent to Vent Stack through liquid seal. The liquid discharge from Vent Scrubber is collected

in Close drain Tank. The drip pan liquid collected from all equipments and inlet manifold skid

is routed to Open Drain Tank. The combined discharge from Closed & Open Drain Tank has

provision to transfer the material to liquid/gas mixture line through a drain pump or directly to

disposal sump or to support vessel as produced water accordingly.

Water Injection line from RP-3 arrives at RC-4 platform. After reaching at RC-4 platform Riser

balcony, it is divided into three lines for RC-4, RC-5 & RC-DM platform use. RC-4 water

injection line shall go to three injection wells. A tapping is taken from this header for Killing

manifold which is required for 9 production wells & 3 Injection Wells at RC-4 platform.

Demulsifier and Depressant Chemicals storage and injection facility are installed on the

platform.


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5.DESIGN BASIS

5.1. DESIGN FLOW RATES

Production Wells 9

Injection Well 3

Liquid production 6000 Tonns/day

Oil 5500 Tonns/day

Water 500 Tonns/day

Maximum liquid per well 1200 Tonns/day

Maximum Gaslift gas for all wells 400,000 NM3/Day

Gaslift gas per Well 10000 - 50000 NM3/DayMaximum Injectivity of an injection

well Upto 1000 m3/day

Notes:

1. Liquid production of 6000 Tonnes/day is the total maximum design liquid capacity for

all 9 wells together.

2. Inlet production Separator Gas capacity shall be 400,000 NM3/day + Associated gas

with the crude oil based on Hysys calculation.


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5.2. OPERATING AND DESIGN CONDITIONS

PRESSURE TEMPERATURE

Operating Design Operating Design

Bar g Bar g C C

Production Header 16-41 80 55 60

Test Header 16-41 80 55 60

Vent Header 2 11.5 55 -48 / 60

Drain Header ATM 11.5 55 60

Gaslift gas 105-110 125 22-30 45

Production Separator 16-41 60 55 60

Vent Scrubber 2 11.5 55 -48 / 60

Pig Launcher/Pig Receiver 16-41 80 55 60

Close Drain Tank 0.7 5.8 55 60

Open Drain Tank ATM 3.5 55 60

5.3. COMPOSITION OF CRUDE OIL FEED


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Component Unit Quantity

N2+RARE Mole % 0.068

CO2 Mole % 0.038

H2S Mole % 0

CH4 Mole % 12.308

C2H6 Mole % 3.099

C3H8 Mole % 6.023

i-C4H10 Mole % 1.52

n-C4H10 Mole % 3.141

i-C5H12 Mole % 3.901

n-C5H12 Mole % 5.409

Pseudo C6 Mole % 6.766

Pseudo C7+ Mole % 57.727

Mol. Wt. g/mole 227.8


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5.4. COMPOSITION OF GASLIFT GAS


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Component Unit Quantity

N2+RARE Mole % 0.175

CO2 Mole % 0.068

H2S Mole % 0

CH4 Mole % 73.622

C2H6 Mole % 12.992

C3H8 Mole % 7.635

i-C4H10 Mole % 1.643

n-C4H10 Mole % 2.358

i-C5H12 Mole % 0.591

n-C5H12 Mole % 0.64

Pseudo C6 Mole % 0.406



Relative density 0.784

Mol. Weight g/mole 22.75

5.5. CHARACTERISTICS OF PSEUDO COMPONENTS


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IN CRUDE OIL Normal Boiling Point (NBP)

Molecular Weight

Std. Ideal Liquid Density

Pseudo C6 66 C 86 663 kg/m3 at 20 C

Pseudo C7+ 358.8 861 - 903.9 kg/m3 at 20 C

Average density 875 kg/m3

IN GASLIFT Normal Boiling Point (NBP)

Molecular Weight

Std. Ideal Liquid Density

Pseudo C6 66 C 86 663 kg/m3 at 20 C

Pseudo C7+ 96 C 100.2 683 kg/m3 at 20 C

Pseudo C8+ 124 C 114.2 702 kg/m3 at 20 C

5.6. METEOROLOGICAL DATA

Climate : Salten Offshore Tropical

Max Wind Speed : 57.4 m/sec

Normal Wind Speed : 8.7 m/sec

Min, Wind Speed : 0.0 m/sec

Barometric Pressure : 996 1022.2 mbar

Ambient Air Quality

Maximum temperature outdoor air : 41 C

Minimum temperature outdoor air : 21 C

Normal temperature outdoor air : 35 C

Dry bulb temperature : 27 0F (-2.8 C) Minimum

Relative Humidity of outdoor air : Maximum 100% to Minimum 56%

Miscellaneous :

Solar Radiation : 335 kcal/ m2hr

Sea Water Temperature : 24.12 C 34.59 C

Sea water Salinity : 293 - 3459 mg/l

Sea water Density : 1018.4 - 1024.19 Kg/M3

Seismic Conditions

Maximum Seismicity : 6 Richter Scale .

5.7. SIMULATION CASES


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The simulation is carried out to know the process conditions at various possible cases based on

operating pressure & properties of crude oil system & the gas lift system.

Case 1 : Oil 6000 Tonns/ DayWater 0 Tonns/ DayProduction Separator Operating Pressure 16 BargGas Lift Operating Temperature 30 CGas Lift Operating Pressure 105 Barg

Case 2 :Oil 6000 Tonns/ DayWater 0 Tonns/ DayProduction Separator Operating Pressure 41 BargGas Lift Operating Temperature 30 CGas Lift Operating Pressure 105 Barg



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Case 4 :Oil 6000 Tonns/ DayWater 0 Tonns/ DayProduction Separator Operating Pressure 41 Barg

Gas Lift Operating Temperature 30 CGas Lift Operating Pressure 110 Barg

Case 5 :Oil 6000 Tonns/ DayWater 0 Tonns/ Day

Production Separator Operating Pressure 16 BargGas Lift Operating Temperature 22 C

Gas Lift Operating Pressure 105 Barg

Case 6 :Oil 6000 Tonns/ DayWater 0 Tonns/ DayProduction Separator Operating Pressure 41 Barg

Gas Lift Operating Temperature 22 CGas Lift Operating Pressure 105 Barg

Case 7 :Oil 6000 Tonns/ DayWater 0 Tonns/ Day

Production Separator Operating Pressure 16 BargGas Lift Operating Temperature 22 C

Gas Lift Operating Pressure 110 Barg


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The above simulation cases have been utilized for preparation of PFD,

Heat and Material Balance, data-sheets and other engineering documents.

The equipment & pipelines are sized according to the governing cases

out of above twenty four different cases.


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6.PROCESS SYSTEM CONTROL PHILOSOPHY

6.1 FACILITIES TO CONTROL

The philosophy of automation, monitoring process control system, safety instrumented system

& hazard-monitoring system is prepared for RC-4 platform following facilities.

Production Wells control through Wellhead Control Panel

Injection Wells control

Process Equipments

Power generation control

Auxiliary Equipments

Fire Fighting Facility

Emergency handling

Accommodation platform control system


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6.2 TYPES OF BASIC CONTROL

The basic control system of RC-4 Wellhead Satellite platform is through PCS & PLC and it is

operated from the Control Room Workstation at RC-4 platform. The monitoring & control

systems of RC-4 Platform are being done through following systems:

Process Control System (PCS)

Safety & Emergency Shutdown System (SSD)

Fire & Gas System RC4 (FGS)

Redundant Local Area Network (R-LAN)

SCADA

Radio Equipment

24 VDC Uninterrupted Power Supply systems for monitoring, control & safety facility including PA/GA & Radio Equipment.

PA/GA System

Data Collection Interface (DCI)

Work-Station PCS/ SSD/ FGS (WS-1)

Wellhead Control Panel (WCP)

Navigation System Panel


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6.3 BRIEF DESCRIPTION OF MAIN CONTROL SYSTEMS

The following control levels should be provided.

Level 0 : Field sensors & execution system

Level 1 : Hardware at the PLC basis (central panel : PCS, SSD, FGS)

Level 2 : SCADA at RC4

(Software & hardware for supervisory control & data acquisition)

6.3.1 PROCESS CONTROL AND MONITORING SYSTEM (PCS):

PCS should do the normal control and monitoring of the process parameter. Moreover PCS at

RC4 platform is having facility to provide safety of personnel, environment, equipment and

platform as a whole. PCS shall be in RC4 Platform Control Room and should have following

minimum control.

Control of Oil & Gas Production, Processing & transportation.

Control of Main & auxiliary process equipments.

Interface with Well Test Unit and Metering Unit.

Control & Monitoring Power Supply System.


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The PCS should serve minimum following functions.

a) Provide graphical display of process information for monitoring and interacting with

facility process equipment.

b) Displaying, managing & archiving the alarms and events from all systems.

c) Continuous recording of process data in historical archive files.

d) Graphical trending of both real time and historical data.

e) Generate production data reports.

f) Interfacing to third-party vendor systems.

g) Provide master communication protocol between all subsystems.

h) PCS shall carry out functions of selfdiagnostics and internal malfunction alarm.

i) PCS shall be tested without process shutdown in case of change of software or loading of

new software.

j) PCS will have hardware panels for visual indication of critical alarms, Critical Valves

status and Critical control switches.

Notes:

1. PCS shall be provided with 100% redundancy to take care of failure condition of Central

Processor (CPU). Both the CPU should have same control computation program in

synchronization so that changeover can be done without any interruption.


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6.3.2 SAFETY & EMERGENCY SHUTDOWN SYSTEM (SSD):

The main purpose of SSD should be to provide following as a minimum.

Safety of staff, environment and process equipment of WHP RC-4 as a whole.

Automatic emergency shutdown of processes and equipment by critical parameters and

also send indispensable signals to other systems.

Provide remote diagnostic calibration and testing.

Provide functions of self-diagnosis and signaling about internal faults with automatic

registration and printing.

SSD shell be comprising of followings.

ESD-A (Emergency Shutdown Abandon Platform)

ESD-C (Shutdown due to emergency on other platforms)

PSD (Process Shutdown)

PSD-GL (Process Shutdown Gaslift)

ESD-GL (Emergency Shutdown Gaslift)

Receiving signal from FGS Panel for ESD-F & ESD-G.

The system SSD includes the equipment of following levels:

Level 0 : Field sensors of critical parameters and execution units of emergency shutdown.


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Level 1 : SSD-Panel (hardware on the PLC basis).

3.3 FIRE & GAS Detection and Fire Fighting Control System at RC-4 (FGS) :

Fire and gas detection and fire-fighting control system (FGS) is a separate dedicated system

and F&G Panel should be installed in RC-4 control room and have autonomous standby power

supply unit. The main purpose of Fire & Gas control panel should be to provide following as a

minimum.

Safety of staff, environment and process equipment of WHP RC-4 as a whole.

Automatic detection of the location of the Fire through UV/ IR flame detectors system,

fusible loop and location of the HC gas leak at the different location on the different decks

of the RC4 platform.

The FGS shall act upon receiving indication from detectors & manual shutdown push

buttons to generate the Emergency Shutdown ESD-F or/and ESD-G signals accordingly

and transfer the critical signals to the SSD and to the other systems.

Automatic Control on RC-4 Fire Fighting System.

The system FGS includes the equipments of the following levels:

Level 0 : F&G field detectors, actuators of RC-4 fire-fighting systems.

Level 1 : FGS-Panel (hardware at PLC base).


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FGS shall provide the following levels of shut down according to level of danger for personnel,

environment, process equipment, and platform as a whole.

ESD-F : Emergency shutdown and process blow-down for personnel safety and equipment/

unit safety. Furthermore APS push buttons for activation of ESD signals to abandon

platform shall be provided.

ESD-G: Emergency shutdown and bringing technological processes and equipment in safe

condition but without pressure blowdown except to release high pressure Gaslift

system.

The F & G system at RC4 shall cover only RC-4 platform. Control system shall execute auto

and remote control of systems and devices for extinguishing of fire at RC-4 (Fire fighting

system fire water pump, fire monitor, fire sprinkler, foam system, CO2 etc) as well as

switching off the HVAC system.

3.4 REDUNDANT LOCAL AREA NETWORK (R-LAN):

Local Information Network should have connection with PCS & PLC (SSD) through

necessary software and external interfaces.

Local Area network (R-LAN) shall transfer the information from PCS to SCADA.

Information by Radio Channel should transfer through R-LAN. It includes ESD-C

information to / from processing platform RP-3 & RP-1.


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3.5 SCADA (Supervisory Control and Data Acquisition)

SCADA should provide receiving / transferring, processing, registration, storage and visual

display of the information on workstations from/to systems PCS, SSD, FGS and receiving /

transferring of the necessary information through DCI by the radio channel. It should be

provided with ability to retrieve from archive the basic process parameters (PT/TT - of each

separate well, PT / TT / LT - of process equipment), Well Test Unit and Metering Unit with

indication in WS-1, demonstrating parameters variation diagrams of each separate well and

technological process for a certain time or for all period of data storage. SCADA should

provide warning signaling (as the controlled process parameters over set points) and alarm

signaling (in emergencies) - light and sound signaling at workstation (WS-1).

3.6 Wellhead Control Panel (WCP):

WCP- should provide with the following remote controls from the system SSD:

a) Shutdown of separate wells (PSD-Closed WSSV, PSD-Closed MSSV) - automatically from

the process control instruments or manually by the command of operator technologist

from workstation WS-1;

a) Shutdown of all wells (ESD-Closed all WSSV / MSSV / SCSSV) - automatically from the

control instruments/systems or manually by the ESD command of operator technologist

from workstation WS-1


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7 OPERATION AND CONTROL OF PROCESS SYSTEMS

Description of the operation and control of the process is divided into different sections as

below.

Well Flow lines

Inlet Manifold

Test Metering Station

Risers

Production Separator

Vent Scrubber

Open & Close Drain system

Gaslift Distribution system

Chemicals Injection

7.1 Well Flow lines Control

There are nine separate wells with wellheads and flow lines at the RC-4 Wellhead platform. The

wellhead of every well is consists of the following main instrumentations.

For isolating a Well, there is underwater Sub Surface Safety Valve (SCSSV) and One master &

One wing valve on the wellhead.


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Master Surface Safety valves (RC4-MSSV-0011/ 0021/ 0031/ 0041/ 0051/ 0061/ 0071/

0081/ 0091).

Wing Surface safety valves (RC4-WWSSV 0011/ 0021/ 0031/ 0041/ 0051/ 0061/ 0071/

0081/ 0091).

Positive Flow chock Valves (RC4-FV-0011/ 0021/ 0031/ 0041/ 0051/ 0061/ 0071/ 0081/

0091).

The chock valves are hydraulically actuated step by step. Choke valve shall close only after

wing valve closes (upon LSD or manual initiation), Choke valve closing time is adjustable.

Reopening of choke valve is only possible only when wing valve is fully open.

The low & high pressure switches are provided on each well flow line after the Chock valves.

The tag numbers are RC4-PSHL 0011/ 0021/ 0031/ 0041/ 0051/ 0061/ 0071/ 0081/ 0091

respectively. PSHL will create electrical signal at high pressure of 50 barg & low pressure of

10 barg, which goes to Well Head Control Panel (WHCP) to shutdown the individual Well.

Each flow line is protected against high pressure by providing a Shutdown valve SDV (RC4-

SDV-0011/ 0021/ 0031/ 0041/ 0051/ 0061/ 0071/ 0081/ 0091 respectively for 9 wells) followed

by three pressure transmitters, which shall be used for shutdown purpose. On actual high

pressure in the individual flow lines, the indication from these three pressure transmitters shall

generate Pressure High High alarm signals in PLC and based on the 2 out of 3 voting system,

PLC shall activate the Pressure High High interlock (RC4-PAHH-1011/ 1021/ 1031/ 1041/

1051/ 1061/ 1071/1081/ 1091 respectively for 9 production wells) which shall shutdown the

SDV in flow line and other appropriate shutdown of the system.

(For detail , see the Cause & Effect Matrix)


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Each well flow line is having a check valve and a safety valve. The operating temperature of

each flow line is 55 degC and the operating pressure range is from 16 to 41 barg.

7.2 Inlet manifold Control

Inlet manifold is having four headers, Production Header, Test Header, Vent Header & Drain

Header.

The production Header is designed to receive the crude oil from all the flow lines together.

Production Header is provided with local pressure & temperature gauges and a pressure

transmitter with Low & High pressure alarms on PCS. To release the pressure of production

header, blowdown valve RC4-BDV-1001 is provided to depressurize it, which operate

automatically on ESD.

A Test header is provided at the Inlet manifold which allows testing of each well separately. To

release the pressure of test header, blowdown valve RC4-BDV-1002 is provided, which operate

automatically on ESD.

The operating pressure of these headers is 16-41 barg & operating temperature is 55

degC.


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7.3 Test Metering Station

As such there is no control on the test metering station. Whenever a well is to be tested for its

components, that flow line is to be lined-up to the test header. From test header, flow is routed

to the metering station. On metering station, a Multi Phase Flow devise is provided which shall

indicate the flow rate of Gas, Oil & Water in the crude oil stream.

7.4 RISERS CONTROL

All the platforms (RC-4, RC-5, RC-DM, RP-1, RP-2, RP-3) produced gas, mixture of oil &

gas, Gaslift gas & water injection are interconnected through risers.

Produced gas from RC-5 (Riser-06) & RC-DM (Riser-07) are coming to RC-4 platform &

from here altogether with RC-4 Produced Gas, these are transferred to RP-3 / RP-2 platform

through Riser-08.

Mixture of oil & gas from RC-DM (Riser-05) is coming to RC-4 platform & from here

altogether with RC-4 they are transferred via Riser 04 to RP-1 through RC-5 platform.

Gaslift gas from RP-3 (Riser-02) is coming to RC-4 platform & from here it is getting

distributed to RC-DM (Riser-03), RC-5 (Riser-01) & RC-4 usage.

Water for injection is coming from RP-3 (Riser-09) on RC-4 platform & from here it is

getting distributed to RC-4, RC-5 (Riser-10) & RC-DM (Riser-11).


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Shutdown Valves SDVs are provided on the Risers where service is Hydrocarbon fluids.

Hand Operated valves are provided in water injection line with limit switches to know the

open & close status of these hand valves on Risers.

In case of emergency on Risers, low low pressure & high high pressure on Produced Gas &

Liquid Risers and only low low pressure on Gaslift Risers are provided to shutdown the

respective SDV and other related SDV accordingly.


7.5 PRODUCTION SEPARATOR V-400 :

Crude Oil from Production header enters into the Production Separator. The operating

pressure of at 16-41 barg and 55C. Production Separator is a 2 phase Horizontal separator to

separate well fluid into gas & liquid phase. Liquid, containing oil & water, is collected in

bottom and provided to stay in the separator for some predetermined time based on the load

to disengage the trapped gases before going out from separator bottom.

Produced gas from separator overhead under separator pressure control is transferred to

processing platform RP-3 while the produced liquid from separator bottom under level

control is transferred to processing platform RP-1 via RC-5 platform.


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7.5.1 PRODUCTION SEPARATOR LEVEL CONTROL:

Production separator liquid level is monitored and controlled by Interface level controller

RC4-LIC-400 on auto mode by operating level control valve RC4-LCV-400, which is located

at separator bottom outlet liquid line. Level controller gets the indication from local level

transmitter RC4-LT-400 that is installed on standpipe of production separator. It keeps a

watch on interface level and hence relative liquid residence time in the separator to ensure

effective separation.

NOTE:

1. On level transmitter failure, its indication should show bad value with alarm and

level controller should be forced automatically to go on Manual mode from Auto

mode, leaving Level Control valve at its last output position.

2. Above action shall give the warning alarm to operation personnel but considering

the normal steady rate, unnecessary shutdown can be avoided.

Another level transmitter RC4-LTS-401 is provided on separator to keep watch on its very

low and very high level and during such condition, this transmitter signal to PLC generate

Low-Low level alarms or High-high level alarms to take proper action through PLC.


However, as same level control valve RC4-LCV-400 is to get trip through PLC in case of low

low level in separator so proper instrumentation system is required for the operation of this

valve during normal and emergency.


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7.5.2 PRODUCTION SEPARATOR PRESSURE CONTROL:

Production separator pressure is monitored and controlled by Interface pressure controller

RC4-PIC-400 on auto mode by operating pressure control valve RC4-PCV-400, which is

located at separator overhead outlet gas line. Pressure controller gets the indication from

local pressure transmitter RC4-PT-400. Depending on the operating scenarios between the

other platform, its set point is to be decided which can vary from 16 barg to 41 barg.

NOTE:

3. On pressure transmitter failure, its indication should show bad value with alarm and

pressure controller should be forced automatically to go on Manual mode from

Auto mode, leaving pressure Control valve at its last output position.

4. Above action shall give the warning alarm to operation personnel but considering

the normal steady rate, unnecessary shutdown can be avoided.

Another pressure transmitter RC4-PTS-402 is provided on separator to keep watch on its

very low and very high pressure and during such condition, this transmitter signal to PLC

generate Low-Low pressure alarms or High-high pressure alarms to take proper action

through PLC.


However, as same pressure control valve RC4-PCV-400 is to get trip through PLC in case of

low low pressure in separator so proper instrumentation system is required for the operation

of this valve during normal and emergency.


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7.5.3 CUSTODY FLOW METERS

Custody flow meter RC4-FT-401 is provided in outlet gas line from separator. Being a custody

meter, proper pressure and temperature compensation is provided on Gas Flow meter by

pressure transmitter RC4-PT-401 & RC4-TT-401. The compensated flow is indicated by RC4-

FI-401 on PCS and the Cumulative flow is indicated by RC4-FQI-401 on PCS.

Custody flow meter RC4-FT-402 is provided in outlet liquid line from separator. RC4- FI-402

indicates the flow on PCS and the Cumulative flow is indicated by RC4-FQI-402 on PCS.

7.5.4 OTHER MONITORING & CONTROL IN PRODUCTION SEPARATOR

a)Gas outlet demister pad differential pressure transmitter is provided to know about the

chocking in the demister pad.

b)Temperature transmitter RC4-TT-402 is provided in liquid phase and its indication RC4-TI-

402 is provided on PCS.

c)Blow-down facility is provided to reduce pressure in the separator in case of fire or other

emergencies.


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7.6 VENT SCRUBBER V-200:

The vent scrubber separates hydrocarbon liquid carried over by the gas in the vent header. The

knocked out vapor goes to vent tip while the accumulated liquid is transferred to closed drain

tank V-301 by gravity. There is provision to empty out the scrubber through Drain pump.

7.6.1 VENT SCRUBBER TEMPERATURE CONTROL :

During emergency release of gas & liquid from process system, there is potential of low

temperature discharge in the vent header & vent scrubber. An immersion electric heater RC4-

HT-200 is provided in the Vent Scrubber in liquid phase, which is operated to control the vent

scrubber liquid phase temperature to avoid congealing of the oil. A temperature switch RC4-

TSH-200 is provided in the liquid phase to control the ON / OFF power to the heater. In normal

operation while no liquid is there, this heater should remain OFF.

The normal operating temperature in the system is 55 degC but the set point of TSH can be

kept much below 55 degC, depending upon the characteristic of the crude in the vent & drain

headers. There is a temperature transmitter RC4-TT-200 in liquid phase whose indication RC4-

TI-200 comes on PCS with high and low alarms on PCS.

7.6.2 VENT SCRUBBER LEVEL CONTROL :

In normal operation, as such there is no level control on vent scrubber. But during any

emergency discharge, during draining of a system or due to any upset, the level can go up. So

to avoid liquid to go into the scrubber overhead vent, a high high level protection is provided.


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Level transmitter RC4-LT-200 on the scrubber shall provide the level indication to PCS with

low & high alarms. Same LT indication is also going to PLC and during very high level, RC4-

LAHH-200 shall initiate the PSD interlock to take the shutdown of the process shutdown.

During low low level, signal RC4-LALL-200 shall come to the soft selector switch RC4-SS-

300 which is located on PCS and if the vent scrubber is selected for drain pump, then RC4-

LALL-200 shall activate USD via RC4-SS-300 which shall send signal to MCC to stop motor

of drain pump RC4-H-311.

7.7 CLOSE DRAIN & OPEN DRAIN SYSTEM:

Overall Drain system consists of Open drain header, closed drain header, Closed drain tank (V-

301), Open drain tank (V-300) and a common reciprocating drain pump RC4-H-311.

Close drain tank is receiving the liquid from closed drain header where equipment draining is

lined up. Vent Scrubber can also be drained into the Close drain tank. In normal operation,

there is no such draining. The open drain tank receives flow from all drip pans liquid collected

from all equipments & inlet manifold skid. Generally this header is not a pressurized header

and should be self-drain towards the open drain tank.

Vapours from V-300 & V-301 are vented to atmosphere via flame arrestor. The HC liquid is

transferred by drain pump RC4-H-311 to mixture of oil & gas liquid line to RP-1. During

maintenance, whatever the liquid is collected in the Drain Tanks, that can be send to disposal

system or produced water to support vessel accordingly.


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7.7.1 OPEN DRAIN & CLOSED DRAIN TANK TEMPERATURE CONTROL:

During emergency release of gas & liquid from process system, there is potential of low

temperature discharge in the vent header & vent scrubber. Vent scrubber can be drained into the

closed drain tank or liquid can come to the tank directly from the drain header. An electric

heater RC4-HT-301 is provided in the Close Drain Tank in liquid phase, which is operated to

control the tank liquid phase temperature. A temperature switch RC4-TSH-301 is provided in

the liquid phase to control the ON / OFF power to the heater. In normal operation while no

liquid is there, this heater should remain OFF.

The normal operating temperature in the system is 55 degC but the set point of TSH can be

kept much below 55 degC, depending upon the characteristic of the crude in the vent & drain

headers. Local temperature gauge RC4-TG-301 is provided on the close drain tank in the

liquid phase.

7.7.2 OPEN DRAIN & CLOSED DRAIN TANK LEVEL CONTROL:

In normal operation, as such there is no level control on both the tank. But during any

emergency discharge, during draining of a system or due to any upset or vessels maintenance

drain, the level can go up. So to avoid liquid to go into the overhead vent, an overflow line is

provided on both the vessels. But for low level protection, level transmitter RC4-LT-300 &

RC4-LT-301 are provided respectively on open & close drain.


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During low low level, signal RC4-LALL-300 OR RC4-LALL-301 shall come to the soft

selector switch RC4-SS-300 that is located on PCS. According to the selection of the

equipment Level in selector switch, the interlock shall initiate to activate USD via RC4-SS-

300. USD shall send signal to MCC to stop motor of drain pump RC4-H-311.

7.8 GASLIFT DISTRIBUTION SYSTEM

7.8.1 GASLIFT METERING STATION

Gaslift gas line of 8, coming from processing platform RP-3 through RISER-02, is reduced to

4 followed by a Shutdown Valve RC4-SDV-800 and Gaslift metering station. Transmitter

RC4-FT-801 monitors Gaslift gas flow towards RC4. The flow device is Simplex change type

orifice fitting with four bored plates, one per range. As the requirement of Gaslift in the well

can vary from minimum required to maximum so to cover the wide range of flow rates with

accuracy, Gas metering station shall provide three flow ranges for which three different bore

size orifice plates are to be kept ready to install in the orifice fittings as required. Based on the

design capacity of Gaslift system and the minimum requirement of Gaslift to one well, the

range of these orifices is to be decided during detailed engineering.

The flow transmitter indication RC4-FI-801A shall display on PCS. Pressure Transmitter RC4-

PT-802 & Temperature Transmitter RC4-TT-801 are provided for pressure & temperature

compensation to the gaslift flow. The compensated flow is indicated by RC4-FI-801 and the

cumulative flow is indicated by RC4-FQI-801 on PCS.


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In emergency on platform or on the gaslift metering station, a blowdown vlave RC4-BDV-801

is provided to release the pressure.

7.8.2 GASLIFT GAS TO INDIVIDUAL WELL

Gaslift from metering station shall go to the gas distribution manifold where gas is distributed

to all wells. Gaslift flow is being controlled towards each well through an angle valve with

diaphragm actuator (RC4-FCV-811/ 812/ 813/ 814/ 815/ 816/ 817/ 818/ 819 respectively for 9

wells). Flow is being monitored by flow transmitters RC4-FT-811/ 812/ 813/ 814/ 815/ 816/

817/ 818/ 819 respectively for 9 wells). The individual flow device is Simplex change type

orifice fitting with four bored plates, one per range.

The requirement of Gaslift in the well can vary from minimum required to maximum or even

intermittent use of gaslift, depending on the oil capacity in the wells. To cover the wide range

of flow rates with accuracy, each line is be provided with four flow ranges for which four

different bore size orifice plates are to be kept ready to install in the orifice fittings as required

by mode of operation. Based on the design capacity of Gaslift system and the minimum

requirement of Gaslift to one well, the range of these orifices is to be decided during detailed

engineering.

A selector switch is provided on PCS for selecting Installed Bore size which shall be the

input to the PLC base controller RC4-FY-811/ 812/ 813/ 814/ 815/ 816/ 817/ 818/ 819

respectively for 9 wells. The PLC based logic shall work according to wide range of gaslift

requirement & header pressure. Accordingly it shall provide the remote set point to the flow

controller RC4-FIC-811/ 812/ 813/ 814/ 815/ 816/ 817/ 818/ 819 respectively for 9 wells

through PCS computer controller RC4-PY-811/812/ 813/ 814/ 815/ 816/ 817/ 818/ 819


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respectively for 9 wells which shall also take the measured value of downstream pressure RC4-

PI-821/ 822/ 823/ 824/ 825/ 826/ 827/ 828/ 829 on PCS through local pressure transmitters

RC4-PT-821/ 822/ 823/ 824/ 825/ 826/ 827/ 828/ 829. For detailed modes of operation, refer

Gaslift Operation philosophy of VSP platforms.

Two chock valves are provided from main header to one bypass header to provide controlled

gas in case of maintenance of the main flow control angle valves.

7.8.3 GASLIFT USE FOR SLUG REMOVAL & FOR GAS DISPOSAL.

As the disposal of Gaslift is related to the underwater pipes before RISERS which are Gaslift

main pipe from RP-3 platform to RC-4 Platform, Gaslift pipe to RC5 & RC-DM platforms, the

take off point of this line are taken directly from three Gaslift Risers at RC4 platform.

A shutdown valve RC4-SDV-802 is provided in the common disposal line. A chock valve is

provided to throttle the flow. As this line is also to be used for removal of the slug

accumulation in the Production separator gas outlet line whose design pressure is 60 barg so

high pressure protection levels are given by providing three pressure transmitters RC4-PT-

803A / 803B / 803C. On actual high pressure in this section of gaslift line after chock valve

during disposal or slug removal, the indication from these three pressure transmitters shall

generate Pressure High High alarm signals in PLC and based on the 2 out of 3 voting system,

PLC shall activate the Pressure High High interlock RC4-PAHH-803 which shall shutdown the

RC4-SDV-802 in the gaslift disposal line.


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As 2nd level of safety, a pressure safety valve RC4-PSV-801 is also provided in this gaslift

section.

As the disposal is to be done from high pressure to low pressure through chock valve, there is

potential of low temperature in this section if the disposal is not controlled properly. So a low

temperature protection is given by providing a temperature transmitter RC4-TT-804 which

shall generate the low temperature alarm signal in PLC and PLC shall activate RC4-TALL-804

to shutdown the RC4-SDV-802 in gaslift disposal line.

7.9 CHEMICAL INJECTION SYSTEM

The Chemical Injection System includes dosing of the following Chemicals:

Depressant

Demulsifier

7.9.1 DEPRESSANT

Depressant Unloading is done from container by Unloading Pumps (H-700A5-1/ H-700A5-2).

There are four Depressant Storage Tanks E-700A2-1, E-700A2-2 with capacity of 10 M3 each

and E-700A3-1 & E-700A4-1 with capacity of 20 M3 each. Chemical can be transferred from

Jack-up drilling Rig to storage tank.


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Depressant Dosing pumps H-700A1-01/700A1-02/ 700A1-03/ 700A1-04/ 700A1-05/ 700A1-

06/ 700A1-07/ 700A1-08/ 700A1-09/ 700A1-10/ 700A1-11 are pneumatic operated pumps and

the pumps discharge has provision to inject the chemical to two different points which are X-

Mas tree at down hole & at upstream of flow choke valve at well head.

To start the dozing pump, instrument air valves (RC4-XV-711/ 712/ 713/ 714/ 715/ 716/ 717/

718/ 719/ 720/ 721) are to be opened which can be done by local hand switches RC4-HS-

711AA / 712AA/ 713AA/ 714AA / 715AA/ 716AA/ 717AA/ 718AA/ 719AA/ 720AA/ 721AA

respectively and similarly to stop the pump, same instrument air valves are to be closed which

can be done by either local hand switches RC4-HS-711AB / 712AB/ 713AB/ 714AB / 715AB/

716AB/ 717AB/ 718AB/ 719AB/ 720AB/ 721AB respectively OR from remote hand switches

RC4-HS-711B/ 712B/ 713B/ 714B/ 715B/ 716B/ 717B/ 718B/ 719B/ 720B/ 721B on PCS.

There is trip of individual pump based on PSD-Well flow lines but the two common

Deprassant Chemical injection pumps H-700A1-10/700A1-11 shall not trip on any individual

Well PSD actuation. But if it is lined up towards any shutdown well then it is required to stop

manually which is to be ensured through proper operating procedure and alarms.

7.9.2 DEMULSIFIER

Demulsifier Unloading is done from container by Unloading Pumps (H-700B5-1/ H-700B5-2).

There are two Demulsifier Storage Tanks E-700B2-1, E-700B2-2 with capacity of 2 M3 each.

Chemical can be transferred from Jack-up drilling Rig to storage tank.


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Demulsifier Dosing pumps H-700B1-01/700B1-02/ 700B1-03/ 700B1-04/ 700B1-05/ 700B1-

06/ 700B1-07/ 700B1-08/ 700B1-09/ 700B1-10/ 700B1-11 are pneumatic operated pumps and

the pumps discharge has provision to inject the chemical to two different points which are X-

Mas tree at down hole & at upstream of flow choke valve at well head.

To start the dozing pump, instrument air valves (RC4-XV-761/ 762/ 763/ 764/ 765/ 766/ 767/

768/ 769/ 770/ 771) are to be opened which can be done by local hand switches RC4-HS-

761AA / 762AA/ 763AA/ 764AA / 765AA/ 766AA/ 767AA/ 768AA/ 769AA/ 770AA/ 771AA

respectively and similarly to stop the pump, same instrument air valves are to be closed which

can be done by either local hand switches RC4-HS-761AB / 762AB/ 763AB/ 764AB / 765AB/

766AB/ 767AB/ 768AB/ 769AB/ 770AB/ 771AB respectively OR from remote hand switches

RC4-HS-761B/ 762B/ 763B/ 764B/ 765B/ 766B/ 767B/ 768B/ 769B/ 770B/ 771B on PCS.

There is trip of individual pump based on PSD-Well flow lines but the two common

Demulsifier Chemical injection pumps H-700B1-10/700B1-11 shall not trip on any individual

Well PSD actuation. But if it is lined up towards any shutdown well then it is required to stop

manually which is to be ensured through proper operating procedure and alarms.

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VIETSOVPETRO - VIETNAMSHEET 1 of 45

5.1.DESIGN FLOW RATES5.2.OPERATING AND DESIGN CONDITIONS5.3.COMPOSITION OF CRUDE OIL FEED5.4. COMPOSITION OF GASLIFT GAS5.5. CHARACTERISTICS OF PSEUDO COMPONENTS5.6.METEOROLOGICAL DATA Seismic Conditions5.7.SIMULATION CASES

Process Control Philosophy Rev A

Documents

control of process systems

separator level control

vent scrubber level

separator pressure control

flow lines control

main control functions

drain tanks level control

types of basic control