v11 produced water

Shell Nigeria Exploration and Production

Company Ltd.

Bonga FPSO

Plant Operating Procedures Manual

Volume 11

PRODUCED WATER TREATMENT SYSTEMS

OPRM-2003-0311

Version: 1.2

This document is not confidential.

The Copyright of this document is vested in Shell Nigeria

Exploration and Production Company Limited. All rights reserved.

Neither the whole nor any part of this document may be

reproduced, stored in any retrieval system or transmitted in any

form or by any means (electronic, mechanical, reprographic,

recording or otherwise) without the prior written consent of the

copyright owner.

Shell Nigeria E & P Company Ltd. Unrestricted

Document Status Information

1.0. DOCUMENT CONTROL

1.1. Change History

Date Version Author Ref

Indicator Change Description

01/03/04 1.0 ODL – Issue of document for

signature.

31/08/05 1.1 ODL – Amendments to:

• Preliminary Pages

• Part 1 Section 2

Paragraphs 3.4.2 and 4.0

Part 2 Section 1:

• Procedure No 1/001

removed

• Pre-start Checks Steps 1

and 5 altered and

addition to Step 2

• Cold Start-up Steps 2

and 3 removed. Steps 6,

7, 10 and 16 altered,

Step 11 added.

• Procedure No 1/005 ERS

2 altered

Part 2 Section 3

Hydrocyclone Back-

flushing Procedure No

3/002 title ‘ Manual

Backwash’ added and

Automated Backwash Steps

1 to 9 added.

30/04/06 1.2 ODL/SNEPCO – Amendments throughout to

address outstanding HOLDs

and to reflect the final as-

built P&IDs.

OPRM-2003-0311 Page ii of xiv 30-April-2006


2.0 PURPOSE

The purpose of this document is to provide guidance on the safe, efficient

and environmentally aware operation of the Produced Water Treatment

Systems.

It is one Volume within an overall suite of Volumes which comprise the

Bonga FPSO Plant Operating Procedures Manual (POPM). The full listing of

Volumes is as follows:

Volume 1 Field and Facilities Overview

Volume 2A Subsea Production System

Volume 2B Subsea Waterflood System

Volume 2C Subsea Control System

Volume 2D Flow Assurance Guidelines

Volume 3 Oil Separation and Treatment

Volume 4 Oil Storage, Handling and Ballast Systems

Volume 5 Oil Metering and Export System

Volume 6 Vapour Recovery Compression System

Volume 7 Field Gas Compression System

Volume 8 Gas Dehydration/Glycol Regeneration Systems

Volume 9 Gas Export/Import/Lift Systems

Volume 10 Flare and Vent Systems

Volume 11 Produced Water Treatment Systems

Volume 12 Waterflood System

Volume 13 Chemical Injection and Methanol Injection System

Volume 14 Fuel Gas System

Volume 15 Heating Medium System

Volume 16 Drainage Systems

Volume 17 Sewage Treatment Systems

Volume 18 Bilge and Oily Water Separation Systems

Volume 19 Inert Gas System

Volume 20 Nitrogen Generation System

Volume 21 Seawater System

Volume 22 Fresh and Potable Water Systems

Volume 23 Diesel Fuel System and Incinerator

Volume 24 Aviation Fuel System

Volume 25 Instrument and Utility Air System

Volume 26 Deck Hydraulic Systems

Volume 27 Fire Protection Systems and Equipment

Volume 28 Safety and Lifesaving Equipment

Volume 29 PSCS and ESS

Volume 30 Power Generation and Distribution Systems

Volume 31 Black Start Procedures

Volume 32 HVAC Systems

Volume 33 Deck Machinery and Mechanical Handling Systems (Cranes, etc)

Volume 34 Telecommunications

Volume 35 Ancillary Living Quarters (ALQ)

OPRM-2003-0311 Page iv of xiv 30-April-2006


3.0 SCOPE

This document provides a detailed description of the plant and equipment

which comprise the Produced Water Treatment Systems and includes step-

by-step guidance on the operation of the system and its equipment, under

both normal and abnormal operation.

4.0 TARGET READERSHIP

All SNEPCO staff, contractors and other third-party personnel who may be

involved in the operation of the Produced Water Treatment Systems onboard

the

Bonga FPSO.

5.0 SPECIAL NOTE

Not applicable.

6.0 ABBREVIATIONS

The abbreviations used within this document are listed at the end of these

introductory pages.

7.0 REFERENCE INFORMATION/SUPPORTING DOCUMENTATION

The primary reference/supporting documents, which have been either used

or referred to in the development of this document, are listed at the end of

these introductory pages. These are part of the available Operational

Documentation, which SNEPCO Offshore Operations (OO) has in place to

support its day-to-day operations. These and many other documents are

available within the SNEPCO Livelink System. Where appropriate, these

documents have been cross-referenced within this document.

OPRM-2003-0311 Page v of xiv 30-April-2006


Abbreviations

AC Alternating Current

ACB Air Circuit-breaker

AEP Authorised Electrical Person

ANSI American National Standards Institute

API American Petroleum Institute

BA Breathing Apparatus

bara Bar Absolute

barg Bar Gauge

BASEEFA British Approvals Service for Electrical Equipment in

Flammable Atmospheres

BBL Barrel

BOPD Barrel of Oil per Day

BPD Barrels per Day

BS&W Base Sediment and Water

BWPD Barrel of Water per Day

CCR Central Control Room

CEP Competent Electrical Person

CI Chemical Injection

CT Current Transformer

CIV Chemical Injection Valve

CV Production Choke Valve

DC Direct Current

DCS Distributed Control System

DE Drive End

DO Digital Output

DPR Department of Petroleum Resources

ECP Engine Control Panel

ESR 1 Process Shutdown

ESR 2 Surface Process Shutdown

ESR 3 Total FPSO Shutdown

ESS Emergency Support System

F&G Fire and Gas

FBHP Flowing Bottomhole Pressure

FC Fail Closed Valve

FCV Flow Control Valve

FG Flow Indicating Gauge

FIC Flow Indicating Controller

FLA First Line Ashore

OPRM-2003-0311 Page vi of xiv 30-April-2006


FO Fail Open Valve

FPSO Floating Production, Storage and Offloading

FS Fuse Switch

FT Flow Transmitter

FTP Flowing Tubing Pressure

FZA Flow Safety Alarm

GA General Alarm

GOR Gas/Oil Ratio

GT Gas Turbine

H High Alarm

HH High Trip

HCU Hydraulic Control Unit

HCV Hand Control Valve

HMI Human Machine Interface

HOV Hand Operated Valve

HP High Pressure

HPI High Performance Insulation

HPU Hydraulic Power Unit

HSE Health, Safety and Environment

HV High Voltage

HVAC Heating, Ventilation and Air Conditioning

Hz Hertz (Frequency)

ID Internal Diameter

IGF Induced Gas Flotation

IGG Inert Gas Generator

IGV Inlet Guide Vane

IP Intermediate Pressure

IS Intrinsically Safe

ISO International Standards Organisation

kW Kilowatt

L Low Alarm

LAT Lowest Astronomical Tide

LC Locked Closed

LCV Level Control Valve

LEL Lower Explosive Limit

LG Level Gauge

LIC Level Indicating Controller

LL Low Trip

LO Locked Open

LOS Line of Sight

LP Low Pressure

OPRM-2003-0311 Page vii of xiv 30-April-2006


LPG Liquified Petroleum Gas

LS Level Switch

LSA Load-shed Application

LSA Low Specific Activity (Scale)

LT Level Transmitter

LV Low Voltage

LZA Level Safety Alarm

MOV Motor Operated Valve

m/s Metre per Second

MSDS Material Safety Datasheets

MW Megawatt

m3 Cubic Metres

MAC Manual Alarm Callpoint

MCC Motor Control Centre

MCCB Moulded Case Circuit-breaker

MEG Mono Ethylene Glycol

MGPS Marine Growth Prevention System

MIS Management Information System

MIV Methanol Injection Valve

MMSCFD Millions of Standard Cubic Feet per Day

NB Nominal Bore

NC Normally Closed

NDE Non-drive End

NDT Non-destructive Testing

NGL Natural Gas Liquid

NO Normally Open

NPSHA Net Positive Suction Head Available

NRV Non-return Valve

O/A/S Off/Auto/Start

OD Outside Diameter

OID Operator Interface Display

OLI On-line Inspection

P&ID Piping and Instrument Diagram

PCF Permit Control Facility

PCV Pressure Control Valve

PDR Pressure Difference Ratio

PDS Differential Pressure Switch

PDT Differential Pressure Transmitter

PFD Process Flow Diagram

PFS Programming Functional Specification

PG Pressure Gauge

PIC Pressure Indicator Controller

OPRM-2003-0311 Page viii of xiv 30-April-2006


PIV Pigging Isolation Valve

PM Production Manifold

PMV Production Master Valve

PPE Personnel Protective Equipment

ppm v/v Part per Million by Volume

ppm wt/wt Parts per Million by Weight

PSCS Process Safety and Control System

PSD Process Shutdown

PT Pressure Transmitter

PTW Permit to Work

PZA Pressure Safety Alarm

RV Relief Valve

RVP Reid Vapour Pressure

RTJ Ring Type Joint

SCSSV Surface Controlled Subsea Safety Valve

SCU Subsea Control Unit

SDV Shutdown Valve

SI Statutory Instrument

SI Switchgear and Instrumentation

Sm3/hr Standard Cubic Metres per Hour

SPM Single Point Mooring

SRB Sulphate-reducing Bacteria

SSDS Safety Shutdown System

SWL Safe Working Load

SWP Safe Working Pressure

SWV Sacrificial Wing Valve

TCV Temperature Control Valve

TDS Total Dissolved Solids

TEG Tri-ethylene Glycol

TG Temperature Gauge

TIC Temperature Indicating Controller

T/T Tangent to Tangent (Vessel Length)

TT Temperature Transmitter

TVP True Vapour Pressure

TZA Temperature Safety Alarm

UCP Unit Control Panel

UEL Upper Explosive Limit

UF Under-frequency

UPS Uninterruptible Power Supply

USD Unit Shutdown

UV Ultraviolet

OPRM-2003-0311 Page ix of xiv 30-April-2006


VCB Voltage Circuit-breaker

VDC Video Display Computer

VDU Visual Display Unit

VFC Vacuum Fused Contactor

VFD Variable Frequency Drive

VRU Vapour Recovery Unit

VT Voltage Transformer

WHRU Waste Heat Recovery Unit

WI Water Injection

WI WOBBE Index

WSV Well Switching Valve

XOV Crossover Valve

OPRM-2003-0311 Page x of xiv 30-April-2006


Reference Information/Supporting Documentation

Project Data

Document No/Ref Document Title

BON-AME-3PP-B-01043-001-

A01

Operator Guide Produced Water System

(System 43)

BON-AME-3PP-B-21423-002-

C06

P&ID LP Separator

BON-AME-3PP-B-21423-003-

C06

P&ID LP Separator

BON-AME-3PP-B-21423-007-

C06

P&ID Bulk Oil Treater

BON-AME-3PP-B-21443-001-

C06

P&ID Produced Water Tank and Pumps

BON-AME-3PP-B-21443-002-

C06

P&ID Hydrocyclone

BON-AME-3PP-B-21443-003-

C06

P&ID Induced Gas Flotation Separator

BON-AME-3PP-B-21448-001-

C06

P&ID Closed Drain and Overboard Header

BON-AME-3GN-B-25082-012-

A01

Sheet 1 of 1

Cause and Effect Diagram Produced Water

System (System 43)

BON-AME-3GN-B-25082-004-

C02

Sheet 1 of 1

Cause and Effect Diagram LP Production

System (System 23)

Vendor Data

Vendor Document Number Document Title

Baker Process Production

and Refining

P237-H-002

Volume 1 of 1

Technical Maintenance Manual

for Induced Gas Flotation

Vessel


and Refining

P237-H-004

Volume 1 of 1

Technical Maintenance Manual

for De-oiling Hydrocyclone

OPRM-2003-0311 Page xi of xiv 30-April-2006


Sulzer Pumps P0001/29/M008/00

1

Sulz-088-340

Technical Manual (Installation,

Operation and Maintenance)


and Refining

P237-M-500

Volume 1 of 1

Datasheets for the

Hydrocyclone Vessel S-4340


and Refining

P237-M-501

Volume 1 of 1

Datasheets for the IGF

Separator V-4341

HEMP Actions

No Description Control Measure ODL Action

1 Valve alignment of

produced water out of the

LP Separators, incorrect

listing of valves.

Update POPM with correct

valve alignment and valve

numbering, ensure latest

available revision of the

documentation is available

prior to writing of POPM.

Procedure

No 1/001 Cold

Start-up Valve

table amended.

2 Priming and starting of

produced water pumps –

confusion due to

statement of cracking

open suction SDV and

starting of pump with

closed discharge valve.

Could pre-filling of piping

be a better option?

The discharge valve is a

CSO valve.

Input more information to

the POPM concerning type

of pump and specific

start-up sequence.

Procedure

Nos 1/001 and

1/002 amended.

3 Charging of the system

with seawater prior to

start-up, POPM is vague

as to the management of

the operation.

Specific description of the

operation to be detailed in

the POPM.

Added to pre-

start checks in

Procedure

No 1/001.

4 Start-up of oil-in-water

analysis is not specific as

to when system should be

placed in operation.

More detail required in the

procedures.

Amended in

Procedure

Nos 1/001

and 1/002.

OPRM-2003-0311 Page xii of xiv 30-April-2006


HAZOP Actions

Action

Number/

Node

Node Description Response to HAZOP Operation Procedure

Section/Procedure

290/6.0

3

Produced Water

Hydrocyclones

Carry out routine

back-flushing once

per shift.

Part 2 Section 3 Procedure

No 3/002.

130/17 Induced Gas

Flotation

Separator

Methanol from

production process

passing overboard

with the produced

water.

Text and references added to

Part 1 Section 1 Paragraph

3.3.

OPRM-2003-0311 Page xiii of xiv 30-April-2006


OPRM-2003-0311 Page xiv of xiv 30-April-2006

Main Table of Contents

Document Status Information

Abbreviations

Reference Information/Supporting Documentation

Part 1 – Technical Description

Section 1 System Overview

Section 2 Detailed Description

Part 2 – Operating Procedures

Section 1 System Operating Procedures

Section 2 Equipment Operating Procedures

Section 3 Supplementary Operating Procedures

Shell Nigeria E&P Company Ltd. Unrestricted

PART 1 TECHNICAL DESCRIPTION



Part 1 Technical Description

OPRM-2003-0311 Page 1 of 1 30-April-2006

Shell Nigeria E&P Company Ltd Unrestricted



Table of Contents

1.0 INTRODUCTION.............................................................................................................2

2.0 PROCESS DESCRIPTION.............................................................................................2

3.0 HEALTH, SAFETY AND ENVIRONMENT (HSE) ..........................................................3 3.1 General................................................................................................................3 3.2 Specific Hazards..................................................................................................4 3.3 Environmental Issues ..........................................................................................4

FIGURES Figure 1.1 – Produced Water System Overview ......................................................................6

Part 1 Section 1 System Overview



1.0 INTRODUCTION All produced water extracted from the Bonga well fluids by the Oil Separation and Treatment System is processed by the Produced Water Treatment System. The produced water treatment facilities ensure the quality of the water discharged to sea meets the required standard of 15ppm (wt) from a maximum inlet hydrocarbon concentration of 1000ppmv.

The Produced Water Treatment System consists of the following major components:

• Produced Water Tank V-4340

• Produced Water Pumps P-4340A/B

• Produced Water Hydrocyclone S-4340

• Induced Gas Flotation (IGF) Separator V-4341

The system is currently rated to process 100,000BWPD of produced water but is designed to accommodate future expansion of up to 160,000BWPD.

2.0 PROCESS DESCRIPTION Refer to Figure 1.1.

The produced water leaving the Oil Separation and Treatment System contains too high a concentration of oil for dumping at sea, and is therefore treated by passing the fluid through the Produced Water Treatment System.

Produced water separated in the LP Separators V-2341A/B and Bulk Oil Treater V-2343 enters the Produced Water Tank V-4340 under the interface level control of these vessels. The combined incoming flow passes into a 20in inlet manifold and mixes with any clean produced water recycled from the hydrocyclone.

Dosing points for the injection of water clarifier and scale inhibitors are located on the produced water outlets from the LP separators.

Produced Water Tank V-4340 is a vertical, two-phase vessel designed to remove dissolved hydrocarbon gases from the incoming produced water. The vapours are released to the first-stage VRU suction scrubber. The produced water tank operates at low pressure to maximise hydrocarbon vapour recovery to the VRU compressor.

Degassed produced water is passed from the tank to the suction of the 100% capacity Produced Water Pumps P-4340A/B. The duty pump discharges the produced water to Hydrocyclone S-4340. The produced water pumps are specifically designed to limit the shearing effect on any oil droplets in the produced water, so as not to adversely affect the oil removal efficiency in the hydrocyclone.

The produced water pumps are protected against operating below the minimum flowrate by a recycle line. When the discharge flow falls below the minimum set point, a recycle flow control valve opens to recycle water from the pump discharge back to the produced water pump.

There is provision to install a third produced water pump (P-4340C) at a later date when the water cut of the Bonga reservoir fluids has increased to a point where the existing capacity of the Produced Water Treatment System is exceeded.

Produced Water Hydrocyclone S-4340 consists of a single hydrocyclone unit, which contains a number of individual hydrocyclone tubes (normally referred to as hydrocyclone liners).




There is provision to install a second produced water hydrocyclone (S-4341) to process the extra produced water in the future.

In the hydrocyclone unit the oil droplets suspended in the produced water are separated from the water by enhanced gravity separation and leave the hydrocyclone through three individual oil reject lines to a common oil reject header for re-processing in the production sump. The denser water phase exits the hydrocyclone at about 40ppm (wt) and discharges into a clean water outlet header.

Clean water from the hydrocyclone is directed to Induced Gas Flotation Separator V-4341, which further reduces the oil-in-water concentration until it is within the required specification of 15ppm (wt) total.

A chemical injection point is provided on the clean water outlet from the hydrocyclone so as to enable water clarifier to be injected to the induced gas flotation separator, if required. The addition of this chemical encourages bonding of the small oil droplets to enhance the performance of the IGF separator.

The induced gas within the IGF separator assists the upward velocity of the oil droplets to float to the surface as a foam, where they are skimmed off and directed to the production sump. Hydrocarbon gas is vented from the IGF separator to the first-stage VRU suction scrubber.

Clean, degassed produced water is discharged to the sea from the IGF separator, under level control. An oil-in-water analyser is provided for monitoring the produced water being dumped overboard. This is located on the downstream pipework of the IGF separator and will alarm to indicate a high level of oil-in-water content.

Final disposal of the produced water takes place through the overboard header and caisson to the sea.

Off-spec produced water which cannot be dumped to sea is switched to the slop oil tank or the primary reception tank.

3.0 HEALTH, SAFETY AND ENVIRONMENT (HSE)

3.1 General The Produced Water Treatment System is located on the vessel topsides and as such forms part of the main topside operating area.

All personnel in the area must have received training in, and be fully conversant with, the following:

• Location and use of fire and safety equipment in the area

• Recognition and response to all the vessel’s visual and audible alarms

• Muster and evacuation procedures

• Escape routes

• Location and use of lifesaving equipment




3.2 Specific Hazards The Produced Water Treatment System handles mainly produced water at relatively low temperature (50°C) and pressure. Therefore, hazards are low compared with other processing systems. However, it is incorrect to assume that no hazards exist. Potential hazards include the following:

• The produced water tank is gas blanketed

• Level control problems in the LP separators or oil treater could result in large quantities of oil reaching the produced water tank

• Level control problems in the LP separators could result in gas blowby, with large volumes of gas flowing to the produced water tank

This system cannot be taken for granted just because it usually contains mostly water.

All personnel must wear the appropriate protective clothing (overalls, safety helmet, gloves, goggles etc) when in the area, and wear hearing protection if noise levels in the area are high.

The Produced Water Treatment System employs various items of rotating equipment which must have all moving parts securely guarded at all times.

3.3 Environmental Issues

3.3.1 Overboard Discharge Since the Produced Water System discharges effluent overboard, environmental issues could arise if the discharge fails to meet the required discharge parameters. However, the final effluent is automatically monitored and if its quality deteriorates below the allowable value, the off-specification water is automatically diverted for further treatment. Diverted water will usually be routed to the dirty slops tank. From there it will be pumped to the LP separator for reprocessing. Refer to Volume 2 Subsea Facilities, Flowlines and Risers for details.

3.3.2 Low Specific Activity (LSA) Naturally Occurring Radioactive Material (NORM) is found throughout the natural environment, including reservoir formations. Formation water (ie produced water) dissolves radioactive salts from the formation rock and brings NORM to the surface with the produced water. The activity concentration of this NORM contamination is very low, and to emphasise that the concentrations are very low, such material is usually referred to as LSA.

Since the levels are typically very low, LSA in produced water is not a problem, unless it becomes concentrated in some manner. As the produced water is subjected to changes in temperature and pressure during the treatment process, dissolved solids may precipitate out of solution and deposit scale and sediment (sludge). Sludge and scale wastes should be removed from production equipment in a safe and controlled manner, and disposed of in a manner that complies with local regulations.




3.3.3 Methanol in Produced Water Methanol injected at the crude oil wells, flowlines and topsides process facilities appears in the produced water. Methanol biodegrades in water, however methanol in high concentrations (>1%) in fresh or salt water can have harmful effects on aquatic flora and fauna within the immediate discharge area.

Under current environmental guidelines and standards for the Petroleum Industry in Nigeria (revised edition 2002) issued by the Department of Petroleum Resources (DPR), methanol discharge from offshore structures is currently unregulated. However, in line with best practice, methanol discharge from Bonga should be kept as low as reasonably practicable.




Figure 1.1 –

Produced Water System Overview

Part 1 Section 1 System Overview OPRM-2003-0311 Page 6 of 6 30-April-2006


Part 1 Section 2 Detailed Description




Table of Contents

1.0 INTRODUCTION.............................................................................................................2

2.0 EQUIPMENT DETAILS ..................................................................................................2 2.1 Produced Water Tank..........................................................................................2 2.2 Produced Water Pumps ......................................................................................3 2.3 Produced Water Hydrocyclone............................................................................4 2.4 Induced Gas Flotation Separator.........................................................................6

3.0 CONTROL AND INSTRUMENTATION..........................................................................7 3.1 Produced Water Tank V-4340.............................................................................7 3.2 Produced Water Pumps P-4340A/B ....................................................................8 3.3 Produced Water Hydrocyclone S-4340 ...............................................................9 3.4 Induced Gas Flotation Separator S-4341..........................................................11 3.5 Overboard Discharge Water Quality..................................................................13

4.0 MODES OF OPERATION.............................................................................................14

5.0 SAFEGUARDING.........................................................................................................14 TABLES Table 2.1 – Produced Water Tank Controllers, Alarms and Trips............................................8 Table 2.2 – Produced Water Pumps Controllers, Alarms and Trips.........................................9 Table 2.3 – Induced Gas Flotation Separator Controllers, Alarms and Trips.........................13 Table 2.4 – Produced Water System Relief Valve Settings ...................................................15 FIGURES Figure 2.1 – Produced Water Tank and Pumping Facilities ...................................................16 Figure 2.2 – Produced Water Hydrocyclone .........................................................................17 Figure 2.3 – Induced Gas Flotation Separator .......................................................................18




1.0 INTRODUCTION The Produced Water Treatment System removes the traces of oil from the water which has been produced with the crude oil from the Bonga formation and undergone separation in the LP separators and bulk oil treater. After treatment, the clean water is discharged overboard.

Major items in the Produced Water Treatment System are as follows:

• Produced Water Tank V-4340

• Produced Water Pumps P-4340A/B

• Produced Water Hydrocyclone S-4340

• Induced Gas Flotation (IGF) Separator V-4341

2.0 EQUIPMENT DETAILS

2.1 Produced Water Tank Equipment Details Tag Number: V-4340

Location: Port Process Module

Manufacturer: IMS

Design: Welded steel with vertical support

Design Temperature: -10°C to 94°C

Design Pressure: +1.034barg/-0.052barg

Capacity: 729.0m3/hr

Refer to Figure 2.1 or P&ID BON-AME-3PP-B-21443-001-C066.

Equipment Description The purpose of Produced Water Tank V-4340 is to collect produced water from the LP separators and bulk oil treater operating at pressures ranging from 20.0barg to 2.4barg, and to provide safe disposal to the first-stage VRU suction scrubber of gases liberated by the pressure reduction in the vessel to 0.5barg.

Because the produced water tank is fed with produced water by process vessels at different pressures, emulsification and oil droplet dispersion may occur in the vessel. Consequently, the size of the next downstream vessel, Induced Gas Flotation Separator V-4341, has been designed to give a long residence time to aid the break-up of emulsions.

Produced Water Tank V-4340 is a vertically mounted vessel which measures 5.486m in diameter and 5.586m in height (tan/tan). The internal surfaces of the tank are epoxy lined to avoid corrosion. The tank has a design pressure of +1.034/-0.052barg, a temperature range of -10 to +94°C and is sized for the future produced water flowrate of 160,000BWPD.




Produced water enters at the top of the tank through a 20in flanged nozzle. The fluid is directed through an internal drop line to the bottom of the tank where it is distributed through a series of 25mm x 230mm slots to minimise splatter. This process, together with the drop in pressure, encourages dissolved hydrocarbon gases to flash-off.

Under normal operating conditions the pressure in the produced water tank is not allowed to exceed 0.5barg, with make-up gas directed through 32-PCV-001 to the tank as necessary. Vacuum Breaker 43-PSV-303, which is set at -26mbarg provides protection against vacuum conditions.

The produced water tank is designed to counteract the adverse effects of FPSO motion, and operates as a two-phase separation vessel approximately half liquid full, with 4 minutes hold-up time between high and low alarm points.

Any separated oil droplets float on top of the water and form a layer over a period of time. Provision is made to drain off or ‘skim’ any such accumulations of oil in the vessel by means of 10 individual valved tappings over the operating range of the vessel with 6in spacing. The tappings are arranged in two groups of five each with a manifold, leading to two tundishes. Skimmed oil is disposed of from each tundish to the Collection Sump S-4701B.

Level Gauges 43-LG-302A and B allow constant monitoring of the level inside the tank. An overflow line is hard piped from the produced water tank to the dirty slops tank.

Degassed produced water flows through a vortex breaker from the tank to the Produced Water Pumps P-4340A/B.

2.2 Produced Water Pumps Equipment Details Tag Number: P-4340A/B


Manufacturer: Sulzer Pumps

Model: VCR 10-14-24A/6 Stage

Driver Rating: 350kW

Voltage: 6.6kV

Suction Pressure: 0.5barg

Discharge Pressure: 12.1barg






Equipment Description The produced water pumps are required to raise the pressure of the degassed produced water from Produced Water Tank V-4340 up to 12barg. This is the required pressure to drive the fluids through the hydrocyclone. There are two identical pump sets provided, one dedicated for duty and the other as standby. The manufacturer of the pump sets is Sulzer Pumps. The produced water pumps are low speed, low sheer, vertical canister pumps, which are specifically designed to limit the shearing effect on any oil droplets in the produced water, so as not to adversely affect the oil removal efficiency in the downstream hydrocyclone. A removable strainer is provided on the produced water pump suction to protect the pump from debris. The pump has six stages and is driven through a Kopflex, disc type, spacer coupling by a 350kW electric motor. The pump bowl is supported by the discharge column, which also houses the line shaft drive to the impellers. At the top of the discharge column is the suction and discharge head, which allows connection of the lines to and from the pump. The suction connection directs produced water into the canister from where the pump draws the fluid. Draining of the suction can and pump casing is achieved by pressurising the suction can with nitrogen. The electric motor driver is mounted vertically upon the suction and discharge head. Produced water leaves the discharge column through an elbow to the discharge nozzle. The line shaft penetrates the elbow to connect to the driver, with containment provided by a John Crane single-cartridge mechanical seal. Each produced water pump has a capacity of 662.5m3/hr (100,000BWPD). Produced water exits the discharge of the duty pump and is directed to Produced Water Hydrocyclone S-4340. The duty pump operates continuously at a constant throughput with Flow Control Valve 43-FCV-321 regulating the discharge flow through a recycle line, from downstream of the hydrocyclone, back to the inlet header for the produced water tank.

2.3 Produced Water Hydrocyclone Equipment Details Tag Number: S-4340 Location: Port Process Module Manufacturer: Baker Process Production and Refining Model: M1150-Km-300# Operating Weight: 7710kg Design Temperature: -10°C to 94°C Design Pressure: 24.1barg Inlet Oil Concentration: 1000ppm Outlet Oil Concentration: <40ppm Capacity: 168.9m3/hr (minimum) to 662.5m3/hr (maximum) Refer to Figure 2.2 or P&ID BON-AME-3PP-B-21443-002-C064.




Equipment Description The hydrocyclone is manufactured to a proprietary design marketed under the trade name of ‘Vortoil’ and consists of four main sections:

• Involute inlet chamber

• Concentric reducing section

• Fine tapered section

• Parallel section

Produced Water Hydrocyclone S-4340 consists of a single hydrocyclone pressure vessel, which contains 241 individual hydrocyclone liners and 30 blanks to permit upgrade for a throughput of 110,000BWPD.

The liners operate in parallel inside the vessel and can be added or removed, and blanked internally to adjust capacity whilst maintaining the required flow through each liner, thereby allowing fine tuning of the hydrocyclone. All hydrocyclone liners are fed from a common inlet nozzle, and each hydrocyclone liner discharges into a common clean water outlet header. The reject oil from each liner is piped individually to a manifold, which has a common outlet for the reject stream.

Driven by the system pressure of 12.1barg (ie produced water pump discharge pressure), the oily water mixture enters each hydrocyclone liner via a tangential inlet to form a vortex. On entering the inlet of the hydrocyclone liner, the produced water undergoes virtually instantaneous separation of oil and water due the cyclonic forces imparted.

Forced down the liner, the fluid is accelerated in the concentric reducing section thus inducing high centrifugal forces. The denser water phase moves outwards passing down the liner and exiting at the clean water outlet, while the lower density oil is drawn into the low pressure core. This last section provides increased residence time for smaller, slower oil droplets to migrate to the core.

Note: The minimum flowrate is 2.0m3/hr per liner. Below this flowrate the centrifugal forces inside the hydrocyclone are too weak to provide efficient separation.

The combination of the back-pressure applied to the clean water outlet (controlled by 43-LCV-301A) and the lower reject pressure (controlled by 43-PDCV-325) causes reverse flow to be induced in the central oil core. The oil reject leaves the hydrocyclone liner through an orifice centrally positioned in the back wall of the involute chamber at the top of the liner.

The clean produced water from the hydrocyclone passes to the induced gas flotation separator, and the rejected oil stream is directed to the production sump.

Limitations on the use of hydrocyclones are as follows:

• The flow through the hydrocyclone must be within the recommended operating range

• The oil-in-water of the feed should not exceed the design limit of 1000ppm

• There should be no device upstream of the hydrocyclone which could reduce droplet size or form emulsions. If small hydrocarbon droplets (ie less than 15 microns) are present in the produced water, a chemical such as polyelectrolyte should be introduced upstream of the hydrocyclone to encourage bonding of the small droplets




In the pipework associated with the hydrocyclone there is a facility to direct produced water from the inlet stream to the reject oil line in order to back-flush the orifice in the reject oil outlets. This facilitates backwashing the holes in the reject plates should they become blocked.

Relief Valve 43-RV-323 provides overpressure protection for the hydrocyclone chamber from a blocked-in thermal/fire condition. This RV is set to relieve to the production relief header at a pressure of 24.1barg.

Relief Valves 43-RV-347A/B, located on the clean produced water header, provide liquid overpressure protection for the induced gas flotation separator. The relief valves are set to relieve to the slop oil or primary reception tank at a pressure of 1.05barg.

2.4 Induced Gas Flotation Separator Equipment Details Tag Number: V-4341


Manufacturer: Baker Hughes Production and Refining

Design: ASME VIII DIV 1 1998 + 2000 Addenda

Operating Weight: 120,320kg

Design Temperature: -10°C to 93.3°C

Design Pressure: 1.049barg/Full Vacuum

Inlet Oil Concentration: 300ppm (maximum)

Outlet Oil Concentration: <15ppm



Equipment Description Induced Gas Flotation Separator V-4341 is a single horizontal depurator vessel consisting of three compartments in series where further recovery of oil not removed by the hydrocyclone takes place. The unit measures 3024mm in width and 11,328mm tan to tan.

The first and second compartments are sub-divided into two cells, each with a 15kW motor-driven rotor mechanism (stirrer/agitator) surrounded by a dispenser, draft tube and standpipe arrangement. These facilities are fitted with blanket gas intake ports to induce gas into the produced water.

‘Clean’ produced water from the upstream hydrocyclone enters the IGF separator, passes through an underflow baffle and enters the first compartment where the entrained oil is removed by the action of the rotation mechanism and the induction of blanket gas in each of the two cells. The rapid rotation of the rotor forms a liquid vortex which extends from the standpipe to just above the tank bottom. This generates a static pressure reduction, resulting in a natural ingestion of gas and a circulating liquid flow from the bottom of the vessel through the draft tube to the rotor.

Note: The flotation process in the IGF separator can be enhanced by the addition of polyelectrolyte chemicals to the produced water passing to the vessel.




The ingested gas, in the form of small bubbles, assists the upward velocity of the oil droplets to float to the surface as a foam, where they are periodically skimmed off via an internal trough and removed under level control to the production sump. The flotation unit operates at 0.3 to 0.35barg, with any hydrocarbon gases breaking out of the produced water being discharged through a vent line to the first-stage VRU suction scrubber.

The produced water then leaves the first compartment via an external nozzle and flows into the second compartment under level control, where the flotation process is repeated but at the lower pressure of 0.05 to 0.1barg.

Produced water flows into the third compartment, or discharge cell, where any remaining oil/gas rises to the surface to be skimmed and collected in a boot, which discharges under level control to the production sump. Clean produced water exits the bottom of the induced gas flotation vessel into the overboard header, under level control, to be dumped overboard. The required overboard oil-in-water quality is 15ppm on a monthly average and 29ppm for a single occurrence.

Pressure Relief Valves 43-RV-348 and 43-RV-349 provide overpressure protection for Compartment 1 and Compartments 2 and 3 respectively. These RVs are set to relieve to the first-stage VRU suction scrubber at 0.5barg.

3.0 CONTROL AND INSTRUMENTATION

3.1 Produced Water Tank V-4340 Produced water discharged from the LP separators and bulk oil treater is combined in a manifold together with any clean water recycled from the produced water hydrocyclone and routed to the produced water tank to be degassed.

3.1.1 Level Control and Protection The liquid level in the produced water tank is maintained at mid height of the vessel to give sufficient hold-up time for any dissolved gases to flash off.

The level is maintained at 2743mm above the bottom of the vessel by Level Indicating Controller 43-LIC-301 acting on 43-LCV-301A, located downstream of the produced water hydrocyclone to maintain back-pressure on the hydrocyclone.

There are High and Low Level Alarms, LAH-301 and LAL-301, derived from 43-LIC-301. The LAH and LAL annunciate in the CCR via the DCS and alert the operator to deviations from the set level control point allowing sufficient time to rectify the problem.

However, should the level in the produced water tank continue to rise or fall, independent High Level Trip LZH-302B or Low Level Trip LZL-302A operates and initiate executive action via the SSDS System. Refer to the latest revision of Cause and Effect Charts for full details on the executive actions resulting from these trips.




3.1.2 Pressure Control and Protection The released gas from the produced water tank is fed directly to the 1st stage VRU suction scrubber. The produced water tank is normally controlled by the VRU 1st stage suction pressure control system when VRU is running and by the atmospheric vent pressure controller system when the VRU is not running.

Pressure Controller 32-PIC-001, which is set at 0.05barg, controls the blanket gas make-up line. It is provided to prevent a vacuum being drawn on the produced water tank if insufficient gas is being liberated from the produced water entering the tank. It is also a means of preventing the ingress of oxygen during normal operations.

Failure of 32-PIC-001 causes a USD shutdown by the activation of Low Low Pressure Trip 32-PZL-002.

Instrument Tag Number

Low Low Trip

Low Alarm

High Alarm

High High Trip

Controller Set Point

43-LZL-302A -27.4%

43-LIC-301 3.8% 66.7% 50%

43-LZH-302B 97.6%

32-PZL-002 0.017barg

32-PIC-001 0.03barg 0.3barg 0.052barg

Table 2.1 – Produced Water Tank Controllers, Alarms and Trips

3.2 Produced Water Pumps P-4340A/B Produced water from Produced Water Tank V-4340 flows to the two produced water pumps, which share the same suction and discharge manifolds. Both pumps are rated for 100% duty.

3.2.1 Pump Control The pumps are normally started and stopped from the DCS. The pumps can also be started and stopped from the starter in the MCC. An emergency stop pushbutton is located adjacent to each pump.

The produced water pumps can be set to operate in duty/standby configuration. The standby pump is automatically started after a time delay of 10 seconds for motor acceleration in the following circumstances:

• The duty pump trips

• The pump selected as duty fails to start

An electronic interlock ensures that both pumps cannot operate simultaneously.




Produced Water Pump P-4340A or B is protected against operation below its minimum flowrate by Flow Indicator Controller 43-FIC-321, which is set at 662m3/hr, minimum flow for a single pump. When the flow falls below this set point, Recycle Valve 43-FCV-321 opens to divert some flow from the discharge of the pump to flow back to the produced water tank, maintaining flow through the pump.

Pressure Controller 43-PIC-336 on the hydrocyclone clean water outlet provides an alternative control signal to the minimum flow controller for the produced water pumps. If the pressure at the clean water outlet of the hydrocyclone, as measured by 43-PIT-336, increases above 8barg, 43-PIC-336 overrides the signal from 43-FIC-321 opening 43-FCV-321 to reduce excessive back-pressure on the clean water outlet of the hydrocyclone and ensure effective operation of the hydrocyclone.

3.2.2 Pump Protection Activation of the high high or low low discharge pressure trip shuts down the respective produced water pump via the SSDS System. Refer to the latest revision of Cause and Effect Charts for full details on the executive actions resulting from these trips.

Pump running indication is annunciated at the DCS via 43-XI-311 and 43-XI-312.


Low Low Trip

Low Alarm

High Alarm

High High Trip


43-PZL-317 7barg

43-PZH-317 17.1barg

43-PZL-318 7barg

43-PZH-318 17.1barg

Table 2.2 – Produced Water Pumps Controllers, Alarms and Trips

3.3 Produced Water Hydrocyclone S-4340 Produced water from Produced Water Pumps P-4340A/B is directed into the produced water hydrocyclone, where the oily produced water is separated into a clean water stream, which exits to the induced gas flotation vessel and a reject oily water stream to the production sump.

3.3.1 Hydrocyclone Operation and Control The two controlled variables, which affect operation of the produced water hydrocyclone, are the flowrate of produced water through the hydrocyclone and the reject ratio (ie the ratio of oil flow rejected to the inlet produced water flowrate).

To operate effectively, the hydrocyclone must operate over a given flow range (2.0m3/hr to 8.5m3/hr per liner). Below the minimum flowrate, insufficient vortex is produced to effect efficient oil/water separation. Above the maximum flowrate, high swirl areas in the liner may result in erosion.




The rate of flow is controlled by the action of produced water tank Level Indicating Controller 43-LIC-301, acting on Level Control Valve 43-LCV-301A on the clean water outlet line, in conjunction with flow and/or pressure control via 43-FIC-321 and 43-PIC-366 acting on the recycle valve 43-FCV-321. These control loops respond to changes in the level, flow and pressure in such a way as to achieve a balance between tight level control and stable flow conditions to the hydrocyclone.

The produced water tank Level Control Valve 43-LCV-301A, located downstream of the produced water hydrocyclone creates a back-pressure on the hydrocyclone. The oil contained in the core of the hydrocyclone is in a low pressure zone and the effect of the external back-pressure causes the oil to reverse its direction and flow back through the reject orifice, to the reject header and on to the production sump.

The reject ratio is defined as the ratio of the reject oil stream flowrate to the inlet volume flowrate of fluid:

Reject Ratio % = Flow Inlet TotalFlow Oil Reject

x 100

Although the reject stream is designated ‘oil’, it typically contains less than 10% oil. For efficient operation, the reject ratio will typically be set at 2.5%.

A minimum reject ratio exists below which the efficiency of the hydrocyclones is severely reduced, the central core becomes unstable resulting in poor separation of oil and water. Extremely high reject ratios also have a similar effect.

The reject ratio can be determined without direct measurement by using the operating pressures across the hydrocyclone. The reject ratio is directly proportional to the Pressure Differential Ratio (PDR), which is defined as:

PDR = PoutPinejPrPin

−−

Where: Pin = Inlet pressure (barg)

Pout = Water outlet pressure (barg)

Prej = Reject pressure (barg)

As the flow through the produced water hydrocyclone varies in response to 43-LIC-301 so the produced water pressure differential, 43-PDIT-325A varies accordingly.

The differential pressure signals generated in 43-PDIT-325A, between oily water inlet and clean water outlet, and 43-PDIT-325B, across oily water inlet and oil reject, are fed to Differential Pressure Ratio Controller 43-PDRC-325, which is located in the produced water hydrocyclone UCP and set at 1.5.

This instrument controls the oil reject flow by modulating Pressure Difference Control Valve 43-PDCV-325 on the reject line to react in order to maintain a constant PDR of 1.5, and hence constant reject ratio.

High and low PDR alarms are provided. The High PDR Alarm 43-PDAH-325, set at 1.6, warns of unnecessarily excessive reject stream flowrates, ie there may be too few hydrocyclone liners installed. A Low PDR Alarm 43-PDAL-325, set at 1.4, warns of impaired separation performance, ie there may be too many liners installed and the number should be reduced by removing liners and installing blanks.




Provided the differential pressure ratio is maintained across the produced water hydrocyclone, the performance is unaffected by alterations in the flowrate of produced water directed to the hydrocyclone, if the flow is within the minimum/maximum flowrate for the liners.

There are no trip conditions for Produced Water Hydrocyclone S-4340.

3.4 Induced Gas Flotation Separator S-4341 Produced water from the hydrocyclone flows to the Petrico induced gas flotation separator for further treatment and reduction of oil-in-water content.

The IGF separator is a horizontal, multi-cell, depurator vessel, which removes the entrained oil particles from the produced water by floating them to the surface using fine gas bubbles. Floating oil is skimmed from the surface of the produced water and the fully treated water is discharged overboard at 15ppm.

3.4.1 Produced Water Level Control and Protection Clean produced water from the hydrocyclone flows under level control of 43-LIC-301 to the IGF separator, as described in Paragraph 3.3.1, and enters the first compartment through an underflow baffle.

The two cells in Compartments 1 and 2 operate together. The produced water leaves the first compartment and enters the second compartment through a second baffle and then passes on to a third, single-cell compartment.

Note: All descriptions in the following paragraphs refer to Compartment 1. The equivalent tag numbers for Compartment 2 are indicated in parenthesis alongside Compartment 1 tag numbers.

The produced water level in the compartment is maintained at a constant level by Level Indicating Controller 43-LIC-502 (512) modulating 43-LCV-502 (512) on the produced water line to the next compartment. High and low level alarms 43-LAH-502 (512) and 43-LAL-502 (512) annunciate in the CCR via the DCS and alert the operator to deviations from the set level control point.

The compartment is fitted with a magnetic type Level Gauge 43-LG-504 (514) and Level Transmitter 43-LZT-504 (514), which provides high high and low low trip signals to the SSDS System.

Produced water from the second compartment flows into the third compartment or discharge chamber, where any remaining oil rises to the surface and is skimmed via the boot to the production sump.

The produced water level in the third compartment is monitored by two level transmitters. Level Transmitter 43-LIT-522 provides the process variable signal to 43-LIC-522, which modulates Level Control Valve 43-LCV-522 on the clean water outlet line and provides high and low level alarms. Level Transmitter 43-LZIT-524 provides high and low trip signals to the SSDS System.

These trip conditions are also repeated via the DCS. Refer to the latest revision of Cause and Effect Charts for full details on the executive actions resulting from these trips.

Clean produced water exits the bottom of the third compartment under the level control of 43-LCV-522 to the overboard header and is directed through the overboard caisson to the sea.




3.4.2 Skimming Control and Protection The system provides an auto-skimming function for Cells 1 and 2. (Cell skimming for the cells is independent of each other.) Oily froth is skimmed from the surface of the produced water into the skimmings boot by raising the level up to 2641mm (configurable) via the DCS facilities at timed intervals (typically 15 to 30 seconds every 30 minutes) using control loops 43-LIC-502 (512) modulating 43-LCV-502 (512). Normally oil is skimmed off on an intermittent basis as the produced water level builds up. There is no requirement to inhibit the high level alarms and trips during skimming. The operator has the facility to disable auto-skimming.

Note: All descriptions in the following paragraphs refer to Compartment 1. The equivalent tag numbers for Compartment 2 are indicated in parenthesis alongside Compartment 1 tag numbers.

The skimmings level in the boot is continuously monitored by two level transmitters. Level Transmitter 43-LIT-501 (511) provides the process variable signal to 43-LIC-501 (511), which modulates Level Control Valve 43-LCV-501 (511) on the skimming outlet line to the Production Sump. Transmitter 43-LZIT-503 (513) provides high and low trip signals to the SSDS System.

Two level transmitters continuously monitor the liquid level in the skimmings boot provided for the third compartment. Level Transmitter 43-LIT-521 provides a signal for level control via 43-LIC-521, which modulates 43-LCV-521 on the skimmings outlet line and provides a high and low level alarm. Transmitter 43-LIT-524 provides high high and low low level trip signals to the SSDS System.

These trip conditions are also repeated via the DCS. Refer to the latest revision of Cause and Effect Charts for full details on the executive actions resulting from these trips.

3.4.3 Pressure Control A 2in blanket gas supply line is hard piped from the Blanket Gas System to the inlet nozzles, which distribute the gas to the IGF separator compartments.

The operating pressure in Compartment 1 is maintained at 0.3barg by blanket gas entering the IGF separator through self-regulating 44-PV-381 on the blanket gas supply line. The flowrate of blanket gas passing to Compartment 1 is measured by Flow Transmitter 44-FIT-382 and displayed on the DCS via 44-FI-382. If the pressure in the compartment increases up to 0.35barg, excess gas is directed to the first-stage VRU suction scrubber through self-regulating 44-PV-344 on the vent line.

Compartments 2 and 3 are maintained at the lower pressure of 0.05barg by blanket gas entering the IGF separator through self-regulating 44-PV-383 on the blanket gas supply line and leaving the cells through 44-PV-383, which is set at 0.1barg. The released gas is fed directly to the vent for safe disposal.

The flowrate of blanket gas passing to Compartments 2 and 3 is measured by Flow Transmitter 44-FIT-384 and displayed on the DCS via 44-FI-384.




3.5 Overboard Discharge Water Quality The quality of the water leaving the clean water compartment is monitored by an oil-in-water analyser 43-AZE-355. The analyser provides a high oil content trip signal to the SDSS logic if the oil content of the discharge water approaches 15ppm. The control logic opens the Shutdown Valve 43-SDV-351 to direct the out-of-spec water to the slop oil tank or primary reception tank and then closes the 43-SDV-381 to the overboard header. When the water quality is restored the operator can rest the trip to direct water overboard.


Low Low Trip

Low Alarm

High Alarm

High High Trip


Compartment 1

43-LZL-504 5.1%

43-LIC-502 22.2% 73.8% 28%

43-LZH-504 86.9%

43-LZL-503 20%

43-LIC-501 37.5% 62.5% 45%

43-LZH-503 75%

Compartment 2

43-LZL-514 5.1%

43-LIC-512 22.2% 73.8% 28%

43-LZH-514 86.9%

43-LZL-513 25%

43-LIC-511 37.5% 62.5% 45%

43-LZH-513 75%

Compartment 3

43-LZL-524 40.7%

43-LIC-522 49.4% 66.8% 56%

43-LZH-524 75.5%

43-LIC-521 37.5% 62.5% 45%

43-LZH-523 75%

Clean Water Discharge

43-AZH-355 25ppm 30ppm

Table 2.3 – Induced Gas Flotation Separator Controllers, Alarms and Trips




4.0 MODES OF OPERATION Oily water from LP separators and bulk oil treater passes into Produced Water Tank V-4340 under interface level control.

The flow of produced water from the tank is controlled via the DCS Level Controller 43-LIC-301, which modulates Level Control Valve 43-LCV-301A on the clean water outlet downstream of the hydrocyclone to maintain the required level in the produced water tank. Any free oil accumulating on the surface of the produced water in the tank is manually skimmed to the collection sump.

Produced water from the tank is directed to Produced Water Pumps P-4340A/B as there is insufficient pressure in the tank to drive it through the hydrocyclone.

The produced water pumps are operated from the DCS on a continuous basis. The pump selected for standby will automatically start in the event of duty pump failure.

Produced Water Hydrocyclone S-4340 operates without intervention provided that the hydrocyclone is maintained within the minimum/maximum flowrates for the total number of liners installed. As the flow of produced water increases, more liners can be brought online as required. The addition of extra liners within the hydrocyclone requires the unit to be taken out of service, isolated and the work carried out under Permit to Work conditions by the vendor.

The hydrocyclone is back-flushed by closing the oil reject line and opening the back-flush valve for 30 seconds (configurable) to ensure the reject flow orifice remains clear and correct separation efficiency is achieved. The back-flush sequence can be manually initiated or set to automatically initiate at a certain time.

Induced gas flotation separator is operated remotely from the DCS to degas and polish the produced water from the hydrocyclone. Normally, oil is skimmed off intermittently as the level of oil at the interface builds up. The duration of skimming and the cycle time are field adjustable.

Regular samples must be taken from the produced water outlet of the IGF separator to ensure that the oil content of the produced water directed to the overboard caisson is within specification.

The produced water to the overboard caisson is also monitored by Oil-in-water Analyser 43-AZE-355, which generates a High Oil Content Alarm on the DCS.

5.0 SAFEGUARDING Produced Water Tank V-4340 is protected against vacuum conditions by the Pressure/Vacuum Relief Valve 43-RV-303. This vacuum breaker is set to operate at 26mbarg (vacuum) and is located in an accessible area.

A Pressure Transmitter 32-PZIT-002 located on the gas outlet line provides a low low trip signal to the ESR and SSDS System. Activation of 32-PZL-002 initiates a shutdown of the Produced Water System (System 43 Shutdown).

The instrument bridles for the produced water tank are fitted with an independent Level Switches 43-LZT-302A and B. These instruments provide trip signals to the ESR and SSDS System.

The primary means of safeguarding Produced Water Pumps P-4340A/B is provided on the ESR and SSDS System via suction valve position indication, system inhibits on pump starts.




Protection for Produced Water Pumps P-4340A/B is provided by Pressure Transmitters 43-PZIT-317/318 located on the pump discharge lines. The ESR and SSDS System receives signals from the pressure transmitter to trip the pump on low low or high high discharge pressure.

Produced Water Hydrocyclone S-4340 does not have any trip functions of any description. Thermal protection for the produced water hydrocyclone is provided by 43-RV-323, on the produced water inlet line which is set to operate at 24.1barg.

Liquid supply overpressure protection from the produced water pumps to the IGF separator is provided by 43-RV-347A and B, which are set to operate at 1.03barg.

Induced Gas Flotation Separator V-4341 is fitted with a series of level transmitters, which monitor the operating levels in the vessels.

The oil/water separation cells are fitted with magnetic type level transmitters, which provide a high high and low low trip signal to the ESR and SSDS System.

All skimming compartments are fitted with independent level transmitters. These instruments provide level control and trip signals to the ESR and SSDS System.

Gas overpressure protection for the IGF separator is provided by Pressure Relief Valves 43-RV-348 and 43-RV-349 set to relieve at 1.0barg.

Equipment Sizing Basis RV Tag No Setting

Produced Water Tank V-4340 Vacuum Basis 43-RV-303 -26mbar

Produced Water Hydrocyclone S-4340

Thermal 43-RV-323 24.1barg

Produced Water to IGF Separator V-4341

Blocked Flow 43-RV-347A/B

1.03barg

IGF Separator V-4341 Gas Flow from fully open Blanket Gas Valve

43-RV-348 43-RV-349

0.5barg 0.5barg

Table 2.4 – Produced Water System Relief Valve Settings


Part 1 Section 2 Detailed Description OPRM-2003-0311 Page 16 of 18 30-April-2006

FFigure 2.1 – Produced Water Tank and PPumping Facilities



FFigure 2.2 – Produced Water Hyydrocyclone



FFigure 2.3 – Induced Gas FFlotation Separator


PART 2 OPERATING PROCEDURES




Part 2 Operating Procedures





Procedure Number

PRODUCED WATER TREATMENT SYSTEMS OPERATING PROCEDURES PROCEDURE NO 1/001: COLD START-UP PROCEDURE NO 1/002: HOT START-UP PROCEDURE NO 1/003: NORMAL OPERATION PROCEDURE NO 1/004: PLANNED SHUTDOWN PROCEDURE NO 1/005: PROCESS AND EMERGENCY SHUTDOWN

Part 2 Section 1 System Operating Procedures



SYSTEM/EQUIPMENT: PRODUCED WATER TREATMENT SYSTEMS

PROCEDURE NO 1/001: COLD START-UP

THE WHOLE OF THIS PROCEDURE MUST BE READ THROUGH AND

FULLY UNDERSTOOD BEFORE CARRYING OUT ANY OF THE FOLLOWING ACTIONS.

INTRODUCTION This procedure details the operator actions required to be carried out on the Produced Water Treatment System for a cold start-up, typically following major maintenance activities.

If the system or parts of the system have been open for maintenance work or for any other reason, the vessels or pipework may contain air/oxygen. Under these circumstances, the affected facilities must be nitrogen purged prior to the introduction of produced water.

Due to the likelihood that the water cuts on the producing wells will increase at a later stage in the field life, it may be necessary to consider starting the produced water treatment system and run on recycle prior to opening the producing wells to prevent the possibility of high water trips on the separation system.

PRECONDITIONS

Supporting Drawings The cold start-up procedure utilises the following P&IDs:

• BON-AME-3PP-B-21443-001-C06

• BON-AME-3PP-B-21443-002-C06

• BON-AME-3PP-B-21443-003-C06

• BON-AME-3GN-B-21448-001-C06

Interface Systems Before the Produced Water Treatment System can be started, the following systems are required to be operational:

• Oil Separation and Treatment. Refer to POPM Volume 3 (OPRM-2003-0303)

• Flare and Vent Systems. Refer to POPM Volume 10 (OPRM-2003-0310)

• Chemical Injection and Methanol Injection System. Refer to POPM Volume 13 (OPRM-2003-0313)

• Fuel Gas System. Refer to POPM Volume 14 (OPRM-2003-0314)

• Drainage Systems. Refer to POPM Volume 16 (OPRM-2003-0316)




• Instrument Air and Utility System. Refer to POPM Volume 25 (OPRM-2003-0325)

• Power Generation and Distribution Systems. Refer to POPM Volume 30 (OPRM-2003-0330)

Pre-requisites • No Permits to Work are in force that may prohibit start-up of the Produced Water System

• After completion of all maintenance activities, all workscope documentation must be completed and signed-off by the relevant authorities before the start-up can commence

• All spades and spectacle blinds are in their correct positions as per the Produced Water System P&IDs listed in Supporting Drawings

• All disturbed flanges and fittings in the system have been nitrogen leak/pressure tested as appropriate, and any leak test certificate signed-off. The produced water facilities have been purged with nitrogen and left with a slight positive nitrogen pressure

• All system pipework drain, vent, purge and sample point valves are closed

• All system equipment drain and vent valves are closed

• All instrument isolation valves are open

• All level bridle process isolation valves are open and vent and drain valves are closed

• The isolation valves for Oil-in-water Analyser 43-AZE-355 are closed

• The DCS, SSDS and ESS control and shutdown facilities are operational and healthy

• Toolbox talks have been held with all directly and indirectly concerned parties outlining the workscope and procedure

• Communications are established between all personnel involved in this procedure

• All level bridle process connection valves are open

PLANT STATUS • The system isolation valves are positioned as indicated in Valve Checklist No 1 Pre-start

Positions – Produced Water System Cold Start-up

• Oil-in-water Analyser 43-AZE-355 has been calibrated and is available for use

• The production sump is prepared to accept reject oil from the produced water hydrocyclone and IGF separator

• The slop oil or primary reception tank are prepared to accept off-spec treated produced water from the induced gas flotation separator

• The overboard header and caisson are prepared to accept on-spec treated produced water from the induced gas flotation separator




VALVE CHECKLIST NO 1: PRE-START POSITIONS: PRODUCED WATER SYSTEM COLD START-UP

Tag No Function Setting Checked

LP Separator V-2341A Refer to P&ID BON-AME-3PP-B-21423-002-C06

23-SDV-045 12in produced water outlet SDV from V-2341A CLOSED

23-BLV-079 12in produced water outlet ball valve from V-2341A upstream of 23-LCV-032

OPEN

23-BLV-082 12in produced water outlet ball valve from V-2341A downstream of 23-LCV-032

OPEN

23-SDV-046 12in produced water outlet SDV from V-2341A to the produced water tank

CLOSED

LP Separator V-2341B Refer to P&ID BON-AME-3PP-B-21423-003-C06

23-SDV-075 12in produced water outlet SDV from V-2341B CLOSED

23-BLV-122 12in produced water outlet ball valve from V-2341B upstream of 23-LCV-062

OPEN

23-BLV-125 12in produced water outlet ball valve from V-2341B downstream of 23-LCV-062

OPEN

23-SDV-076 12in produced water outlet SDV from V-2341B to the produced water tank

CLOSED

Bulk Oil Treater V-2243 Refer to P&ID BON-AME-3SP-B-21423-007-C06

23-SDV-143 12in SDV at outlet from V-2343 CLOSED

23-BLV-220 8in ball valve at inlet to 23-LCV-134 OPEN

23-BLV-223 8in ball valve at outlet from 23-LCV-134 OPEN

23-BLV-224 6in ball valve at 23-LCV-134 bypass CLOSED

Produced Water Tank and Pumps Refer to P&ID BON-AME-3PP-B-21443-001-C06

44-BLV-280 Isolation Block Valve for Fuel Gas Supply to Tank upstream of 32-PCV-001

LOCKED OPEN

44-BLV-281 Isolation Block Valve for Fuel Gas Supply to Tank downstream of 32-PCV-001

LOCKED OPEN

43-BLV-233 Isolation Valve on Skim at Nozzle N6A CLOSED

43-BLV-238 Isolation Valve on Skim at Nozzle N6B CLOSED

43-BLV-234 Isolation Valve on Skim at Nozzle N6C CLOSED

43-BLV-239 Isolation Valve on Skim at Nozzle N6D CLOSED

43-BLV-235 Isolation Valve on Skim at Nozzle N6E CLOSED

43-BLV-240 Isolation Valve on Skim at Nozzle N6F CLOSED

43-BLV-236 Isolation Valve on Skim at Nozzle N6G CLOSED




VALVE CHECKLIST NO 1: PRE-START POSITIONS: PRODUCED WATER SYSTEM COLD START-UP (cont’d)


43-BLV-241 Isolation Valve on Skim at Nozzle N6H CLOSED

43-BLV-237 Isolation Valve on Skim at Nozzle N6J CLOSED

43-BLV-242 Isolation Valve on Skim at Nozzle N6K CLOSED

43-BLV-200 Isolation Valve on Drain Line at Produced Water outlet from Tank

CLOSED AND BLANKED

43-BLV-243 43-LIT-301 vent equaliser to tank OPEN

43-SDV-314 Produced Water Pump P-4240A Suction Valve CLOSED FOR START-UP

43-BLV-203 P-4240A Discharge Block Valve CAR SEAL OPEN

43-SDV-315 Produced Water Pump P-4240B Suction Valve CLOSED FOR START-UP

43-BLV-206 P-4240B Discharge Block Valve CAR SEAL OPEN

43-GTV-202 P-4340A Suction Can Vent to Tank LOCKED OPEN

43-GTV-204 P-4340B Suction Can Vent to Tank LOCKED OPEN

43-GTV-203 P-4340A Suction Can Vent to Atmos CLOSED

43-GTV-205 P-4340B Suction Can Vent to Atmos CLOSED

Hydrocyclone Refer to P&ID BON-AME-3PP-B-21443-002-C06

43-BLV-207 Isolation Valve on Produced Water Inlet to Hydrocyclone

CLOSED FOR START-UP

43-BLV-227 Isolation Valve on Bypass Line for Produced Water Hydrocyclone S-4340

CLOSED

43-BLV-211 Isolation Valve on Clean Water Outlet from the Hydrocyclone

CLOSED FOR START-UP

43-BLV-213 Isolation Valve on Produced Water Line to Separator upstream of 43-LCV-301A

OPEN

43-BLV-215 Isolation Valve on Produced Water Line to Separator downstream of 43-LCV-301A

OPEN

44-GTV-200 Isolation Valve on 43-LCV-301A Bypass Line LOCKED CLOSED

43-BLV-229 Isolation Valve on Produced Water Recycle Line downstream of 43-FCV-321

LOCKED OPEN

44-BLV-249 Isolation Valve on Oil Reject Line for Hydrocyclone upstream of 43-PDCV-235

CLOSED FOR START-UP

44-BLV-251 Isolation Valve on Oil Reject Line for Hydrocyclone downstream of 43-PDCV-325

OPEN






43-BLV-245 Hydrocyclone Vent Valve on 43-RV-323 Relief Line

CLOSED

43-BLV-246 Hydrocyclone Drain Valve at Nozzle N5A CLOSED

43-BLV-247 Hydrocyclone Drain Valve at Nozzle N5B CLOSED

Induced Gas Flotation Separator Refer to P&ID BON-AME-3PP-B-21443-003-C06

43-BLV-216 Isolation Valve on Produced Water Inlet to IGF Separator

CLOSED FOR START-UP

43-BLV-230 Isolation Valve on Bypass Line for IGF Separator

CLOSED

43-BLV-218 Isolation Valve on Produced Water Line from IGF Separator upstream of 43-LCV-522

OPEN

43-BLV-221 Isolation Valve on Produced Water Line from IGF Separator downstream of 43-LCV-522

OPEN

43-BLV-222 Isolation Valve on 43-LCV-522 Bypass Line CLOSED

43-SDV-351 Shutdown Valve on Produced Water outlet to Slop Oil or Primary Reception Tank

OPEN

43-BLV-231 Upstream Isolation Valve for 43-RV-354 (43-RV-354 has been removed. Isolation valve will be locked open only if RV is re-installed)

CLOSED

43-BLV-260 Isolation Valve on Compartment 1 Skimmings Line upstream of 43-LCV-501

OPEN

43-BLV-262 Isolation Valve on Compartment 1 Skimmings Line downstream of 43-LCV-501

OPEN


OPEN


OPEN


OPEN


OPEN

43-SDV-381 Shutdown Valve on Produced Water outlet to Overboard Header

CLOSED

43-BLV-272 Isolation Valve on Compartment 1 Drain Line CLOSED

43-BLV-273 Isolation Valve on Compartments 2 Drain Line CLOSED

43-BLV-274 Isolation Valve on Compartment 3 Drain Line CLOSED

44-BLV-285 1st in Line Isolation Valve on Blanket Gas Line to IGF Separator upstream of 44-PV-381

OPEN






44-GTV-204 2nd in Line Isolation Valve on Blanket Gas Line to IGF Separator upstream of 44-PV-381

OPEN

44-GTV-200 Isolation Valve on to Blanket Gas Line to IGF Separator downstream of 44-FIT-382

LOCKED OPEN

44-BLV-292 Isolation Valve for Blanket Gas to IGF Separator Cell 1

OPEN

44-BLV-255 1st in Line Isolation Valve on Blanket Gas Line to IGF Separator upstream of 44-PV-383

OPEN

44-GTV-205 2nd in Line Isolation Valve on Blanket Gas Line to IGF Separator upstream of 44-PV-383

OPEN

44-GTV-201 Isolation Valve on to Blanket Gas Line to IGF Separator downstream of 44-FIT-384

LOCKED OPEN

44-BLV-293 Isolation Valve Blanket Gas to IGF Separator Compartment 2

OPEN

43-BLV-267 Isolation Valve on Compartment 1 Vent Line upstream of 43-PV-344

OPEN

43-BLV-268 Isolation Valve on Compartment 1 Vent Line downstream of 43-PV-344

OPEN

43-BLV-269 Isolation Valve on Compartments 2 and 3 Vent Line upstream of 43-PV-345

OPEN

43-BLV-270 Isolation Valve on Compartments 2 and 3 Vent Line downstream of 43-PV-345

OPEN




COLD START-UP OVERRIDES: PRODUCED WATER TREATMENT SYSTEM During the Cold Start-up of the Produced Water Treatment System the following inputs to the Safety Shutdown System (SSDS) require to be overridden until steady operating conditions are achieved.

Tag No Equipment Description

None




PRE-START CHECKS AND CONDITIONS

Step Action

1 ENSURE that blanket gas is lined up for use in Produced Water Tank V-4340 via Pressure Control Valve 32-PCV-001, with controller on Auto and a set point of 0.052barg.

2 FILL Produced Water Tank V-4340 with utility seawater, using suitably rated hoses and connections via the unused 3in level transmitter connection.

Slowly RAISE the level in the tank to just above the normal operating level. ISOLATE the seawater supply, remove the filling hose and replace the blank(s) when the produced water tank is at the required level.

Alternatively, a vessel can be filled with produced water using the following process:

• ALIGN the produced water outlet lines from LP Separators A and B, and bulk oil treater to the produced water tank by OPENING Shutdown Valves 23-SDV-045/046, 23-SDV-075/076 and 23-SDV-143 respectively

• SET the interface level controllers for the LP separators and bulk oil treater to MANUAL and OPEN the produced water level control valves (to approximately 10%) if water is available in the separators to FILL the produced water tank until the normal working level is reached

3 ENSURE electrical power is available for Produced Water Pumps P-4340A/B main drive motors and the pumps are ready for use.

4 ENSURE that Produced Water Hydrocyclone S-4340 is ready for use.

5 ENSURE that blanket gas is available from the Fuel Gas System for use in Induced Gas Flotation Separator V-4340. CHECK that self-regulating 44-PV-381 is set to control Compartment 1 pressure at 0.3barg and 44-PV-383 is set to control the pressure of Compartments 2 and 3 at 0.05barg. ENSURE that 44-PV-344 and 44-PV-345 on the vent lines are set at 0.35barg and 0.1barg respectively.

6 FILL the induced gas flotation separator with utility seawater, using suitably rated hoses and connections.

Slowly RAISE the level in all cells to just above the normal operating level. ISOLATE the seawater supply, remove the filling hose and replace the blank(s) once the induced gas flotation separator is at the required level.

7 ENSURE electrical power is available for all four Stirrer Motors V-4341-MM 01A, B, C and D.

8 If installed, ENSURE that the water clarifier injection facilities are ready and primed to point of injection at the produced water inlet to the induced gas flotation separator.

Note: At the present time there is no permanent connection for water clarifier. There is an injection point, however it is not in service at present.

9 ENSURE that the water clarifier and scale inhibitor facilities are ready and primed to point of injection at the produced water outlet from LP Separators A and B.

10 Before starting either of the produced water pumps CHECK the oil level in the thrust bearing housings and TOP-UP as necessary.




Step Action

11 Fill the line from the hydrocyclone to 43-LCV-301A with utility seawater via the connection for the future hydrocyclone. This will prevent water hammer and hydraulic shock on produced water pump start-up.

12 SET 43-LIC-502 the produced water level in Compartment 1 of the IGF separator to AUTO at 28% (2546mm). Level Controller 43-LIC-502 is configured to operate over the normal range and modulate 43-LCV-502 on the produced water line to Compartment 2, as required.

13 SET 43-LIC-512 for the produced water level in Compartment 2 of the separator to AUTO at 28% (2546mm). Level Controller 43-LIC-512 is configured to operate over the normal range and modulate 43-LCV-512 on the produced water line to the discharge compartment as required.

14 SET Level Controller 43-LIC-522 for the depurator to AUTO at 56% (1590mm). This is to maintain the clean water level in the discharge compartment at the centre line. ENSURE 43-LCV-522 opens to maintain the level at this point and discharge the vessel contents to the slop oil or primary reception tank.




COLD START-UP PROCEDURE

Step Action

1 ENSURE that the Oil Separation and Treatment Facilities are in operation and produced water is available from the LP Separators V-2341A/B and Bulk Oil Treater V-2343 at the normal operating pressure and flow.

2 SET Level Controller 43-LIC-301 for produced water tank to MANUAL with the Level Control Valve 43-LCV-301A on the produced water line to the IGS separator fully closed. This is a temporary setting for start-up.

3 OPEN Suction Valve 43-SDV-314 and OPEN pump canister Vent Valve 43-BLV-224 to allow the canister to FILL through the pump.

4 CLOSE the pump canister Vent Valve 43-BLV-224 when produced water shows at the vent tundish.

5 FILL and PRIME Produced Water Pump P-4340B, following an identical procedure detailed for P-4340A in Steps 5 and 6.

6 SET Flow Controller 43-FIC-321 for the Produced Water Treatment Systems to Auto with a set point of 622.5.

Note: 43-PIC-336 is only active once the pressure exceeds 8.0barg. When the pressure is below at 8.0barg, 43-FIC-321 is in control and it is not possible to set the set point for 43-PIC-336.

7 OPEN the Hydrocyclone Bypass Valve 43-BLV-227.

8 SELECT Produced Water Pump P-4340A or B for duty and standby operation then START the duty selected pump from the DCS and establish a flow through the recycle loop on pressure control.

9 SET Pressure Differential Ratio Controller for 43-PDRC-325 (43-PDRC-325-R) for the produced water hydrocyclone at 1.5.

10 SET 43-PDRC-325 to MANUAL and ensure valve 43-PDY-325 is fully closed.

11 PARTIALLY OPEN the manual isolation valve 43-BLV-207 on the produced water inlet to the hydrocyclone to bleed water into the hydrocyclone pressure vessel. Pressurisation should take approximately 90 seconds. Once pressurised fully, open the produced water inlet valve 43-BLV-207.

Note: Care should be taken to pressurise the vessel slowly as rapid pressurisation can damage the hydrocyclone liners.

12 OPEN 43-BLV-216, the block valve downstream of 43-LCV-301A.

13 SLOWLY OPEN the vent valve 43-BLV-245 for the hydrocyclone vessel to expel any air. FILL the hydrocyclone with produced water, using the isolation valve on the vent line for control. Avoid excessive liquid carryover by closing the vent valve after a short time period.

14 SLOWLY OPEN the clean water outlet 43-BLV-211 for the hydrocyclone vessel. This will fill and pressurise the clean water outlet from the hydrocyclone against 43-LCV-301A in the produced water line to the induced gas flotation separator.




Step Action

15 Slowly CLOSE Hydrocyclone Bypass Valve 43-BLV-227. This will pressurise the clean water outlet from the hydrocyclone against 43-LCV-301A in the produced water line to the induced gas flotation separator.

16 CAR SEAL closed Hydrocyclone Bypass Valve 43-BLV-227.

17 Once the pressure in the clean water outlet header increases to 8barg, as indicated by 43-PIC-336, ENSURE Flow Control Valve 43-FCV-321 opens to induce flow through the hydrocyclone. The oil reject line is still isolated at this point.

18 CHECK the amperage on the pump.

19 Two minutes after start-up, OPEN the isolation valve 43-BLV-249 and begin cracking open 43-PDCV-325 for the reject stream on the hydrocyclone to allow reversal of the central oil core and separation to take place.

20 Gradually open 43-PDCV-325 until the PDRC is 1.5, then SET to AUTOMATIC with a set point of 1.5. If the flow through the hydrocyclone is within the correct limits (as measured by the reject ratio) the unit will quickly produce the required oil/water separation.

WHEN STARTING UP A HYDROCYCLONE ALWAYS OPEN THE REJECT VALVES LAST TO MINIMISE THE POSSIBILITY OF REJECT BLOCKAGE.

21 CONFIRM that the expected differential pressure across the hydrocyclones package as a function of flow corresponds with the predicted flow, 168.9m3/hr minimum flow to 728.8m3/hr maximum flow.

22 RESET Level Controller 43-LIC-301 for produced water tank to AUTO with a set point of 50% (2743mm). ENSURE the Level Control Valve 43-LCV-301A on the produced water inlet line to the IGF separator opens to maintain the level.

23 CONFIRM Shutdown Valve 43-SDV-351 on the produced water disposal line from the IGF separator to the slop oil or primary reception tank is open.

24 MONITOR the operating level in the four cells included in Compartments 1 and 2 of the IGF separator. Each cell is provided with a rotor mechanism connected to a stirrer/agitator, which assists the upward velocity of any oil droplets in the produced water.

25 Once the level in each cell reaches the maximum operating level SWITCH ON the stirrer/agitator. This is to direct the oil froth to the skimming compartments.

26 SET Level Controllers 43-LIC-501, 43-LIC-511 and 43-LIC-521 for the skimming compartments to AUTO at the required set points of 45% (2112mm), 45% (2112m) and 45% (1220mm) respectively. Oil recovered in the skimming compartments is directed to the Production Sump via 43-LV-501, 43-LV-511 and 43-LV-521.




Step Action

27 OPEN the isolation valves for oil-in-water analyser 43-AZE-355 to put the analyser online.

28 ENSURE that the Produced Water Treatment System is reducing the oil-in-water content effectively. Collect samples of the inlet and outlet from the hydrocyclone pressure vessel and separator.

29 ENSURE that the Produced Water Treatment System is reducing the oil-in-water content effectively. Collect samples from the outlet from the IGF separator.

30 Once the produced water discharged from the IGF separator is at the required specification of 15ppm, confirmed by lab testing, OPEN Shutdown Valve 43-SDV-381 on the produced water disposal line to the overboard caisson. CLOSE 43-SDV-351 to the slop oil or primary reception tank.

Note: If the oil-in-water content monitored by the oil-in-water analyser 43-AZE-355 reaches 15ppm, the water will automatically be directed to the slop tank/reception tank via 43-SDV-351 and overboard discharge will be stopped by closure of 43-SDV-381.

31 When the Produced Water System is operating satisfactorily REMOVE the start-up overrides detailed in the start-up overrides table.

32 START the injection of water clarifier and scale inhibitor on the produced water outlet of LP Separators A and B as required.





PROCEDURE NO 1/002: HOT START-UP



INTRODUCTION The Hot Start-up Procedure provides a safe and efficient means of starting up the Produced Water Treatment System following the resolution of a trip situation. The reason for the Produced Water Treatment System trip has been established, the situation rectified and the system is ready to be re-started.

Due to the likelihood that the water cuts on the producing wells will increase at a later stage in the field life, it be necessary to consider starting the produced water treatment system and run on recycle prior to opening the producing wells to prevent the possibility of high water trips on the separation system.

PRECONDITIONS

Supporting Drawings The Hot Start-up Procedure utilises the following P&IDs:

• BON-AME-3PP-B-21443-001-C06

• BON-AME-3PP-B-21443-002-C06

• BON-AME-3PP-B-21443-003-C06

• BON-AME-3GN-B-21448-001-C06

Interface Systems Before the Produced Water Treatment System can be re-started, the following systems are required to be operational:

• Oil Separation and Treatment. Refer to POPM Volume 3 (OPRM-2003-0303)


• Seawater Flooding System. Refer to POPM Volume 12 (OPRM-2003-0312)







• Instrument Air and Utility System. Refer to POPM Volume 25 (OPRM-2003-0325)

• Power Generation and Distribution Systems. Refer to POPM Volume 30 (OPRM-2003-0330)

Pre-requisites

• No Permits to Work are in force that may prohibit re-start of the Produced Water Treatment System

• The DCS, SSDS and ESS control and shutdown facilities are operational and healthy

• It is assumed that in a short-duration shutdown, it is unlikely that spades or spectacle blinds would be moved, isolation block valves operated, or drain and vent valves opened, unless required to take corrective action on the cause of the shutdown

• All shutdown valves are set in their respective positions as per Hot Valve Checklist No 1 Produced Water Treatment System. It is assumed that all manual isolation valves have remained in their normal operating positions with the exception of the hydrocyclone valves, which require to be closed prior to a re-start of the facility

PLANT STATUS • Levels, pressures and temperatures throughout the Produced Water Treatment System

have remained within the normal operating range. The produced water pumps, hydrocyclone, induced gas flotation separator and all associated pipework are fully charged with produced water

• The system isolation valves are positioned in their normal operating position except for valves shown on Valve Checklist No 1 Hot Start Positions

• The production sump is prepared to accept reject oil from the produced water hydrocyclone

• The slop oil or primary reception tank are prepared to accept off-spec treated produced water from the induced gas flotation separator

• The overboard header and caisson are prepared to accept on-spec treated produced water from the induced gas flotation separator




VALVE CHECKLIST No 2: HOT START POSITIONS: PRODUCED WATER TREATMENT SYSTEM


LP Separator V-2341A Refer to P&ID BON-AME-3PP-B-21423-002-C06

23-SDV-045 LP Separator V-2341A Produced Water Outlet Valve

CLOSED

23-SDV-046 LP Separator V-2341A Produced Water Outlet Valve

CLOSED

LP Separator V-2341B Refer to P&ID BON-AME-3PP-B-21423-003-C06

23-SDV-075 LP Separator V-2341B Produced Water Outlet Valve

CLOSED

23-SDV-076 LP Separator V-2341B Produced Water Outlet Valve

CLOSED

Bulk Oil Treater V-2243 Refer to P&ID BON-AME-3SP-B-21423-007-C06

23-SDV-143 Bulk Oil Treater V-2343 Produced Water Outlet Valve

CLOSED



CLOSED FOR START-UP

44-BLV-249 Isolation Valve on Oil Reject Line for Hydrocyclone upstream of 43-PDCV-325

CLOSED FOR START-UP

44-BLV-251 Isolation Valve on Oil Reject Line for Hydrocyclone downstream of 43-PDVC-325

OPEN

43-BLV-211 Isolation Valve on Oil Reject Line for Hydrocyclone

CLOSED FOR START-UP

Induced Gas Flotation Separator Refer to P&ID BON-AME-3PP-B-21443-003-C04

43-SDV-351 Shutdown Valve on IGF Separator produced water outlet to Slop Oil or Primary Reception Tank

OPEN

43-SDV-381 Shutdown Valve on IGF Separator produced water outlet to Overboard Header

CLOSED




HOT START-UP OVERRIDES: PRODUCED WATER SYSTEM During the Hot Start-up of the Produced Water Treatment System the following inputs to the Safety Shutdown System (SSDS) may require to be overridden until steady operating conditions are achieved.

Tag No Equipment Description

None




HOT START-UP PROCEDURE

Step Action

1 CONFIRM that the SSDS System has been reset.

2 ENSURE 43-PIC-336 for the Produced Water Treatment System is SET to 8barg in AUTO mode. The output from 43-PIC-336 is used as the set point for flow controller 43-FIC-321.

3 ENSURE 43-FIC-321 is SET to CASCADE, using 43-PIC-336 as the set point for flow.

4 SET Pressure Differential Ratio Controller 43-PDRC-325 for the produced water hydrocyclone is SET at 1.5 in MANUAL mode.

5 ENSURE that 23-LCV-032 and 23-LCV-062 for the produced water outlet from LP Separator V-2341A and B, respectively, are closed.

6 RESET and OPEN LP Separator V-2341A and B produced water outlets 23-SDV-045/046 and 23-SDV-075/076 respectively.

7 ENSURE that 23-LCV-134 for the produced water outlet from Bulk Oil Treater V-2343 is closed.

8 RESET and OPEN 23-SDV-143 on Bulk Oil Treater V-2343 produced water outlet to the produced water tank.

9 ENSURE Level Controller 43-LIC-301 for produced water tank is SET to AUTO at a setpoint of 50% (2743mm).

10 OPEN the Hydrocyclone Bypass Valve 43-BLV-227.

11 RE-START the duty Produced Water Pump P-4340A or B from the DCS and establish a flow through the recycle loop on pressure control.

12 PARTIALLY OPEN the clean water outlet valve 43-BLV-211 for the hydrocyclone and allow the hydrocyclone vessel to pressurise. Pressurisation should only take a few seconds as the vessel is liquid filled. Once pressurised, the outlet valve 43-BLV-211 can be fully opened.

13 PARTIALLY OPEN the produced water inlet valve 43-BLV-207 for the hydrocyclone then open the inlet valve fully.

14 Two minutes after start-up, OPEN the isolation valve 43-BLV-249 on the reject oil stream.

15 Slowly open 43-PDIC-325 to start reject flow. Open 43-PDIC-325 until DPR is approximately 1.5. Set controller to AUTO mode with a set point of 1.5.

WHEN STARTING OR RE-STARTING FULL HYDROCYCLONES ALWAYS OPEN THE REJECT VALVES LAST TO MINIMISE THE POSSIBILITY OF

REJECT BLOCKAGE.




Step Action

16 OPEN the LCVs on the LP separators and bulk oil treater as required to direct produced water from the oil separation and treatment system to the produced water tank.

17 Slowly CLOSE Hydrocyclone Bypass Valve 43-BLV-227 as the LCVs on the LP separators and bulk oil treater are opened.

18 CAR SEAL Closed Hydrocyclone Bypass Valve 43-BLV-227.

19 ENSURE Level Controllers 43-LIC-502, 43-LIC-512 and 43-LIC-522 for the water levels in the IGF separator are set to AUTO at the required set points of 28% (2546mm), 28% (2546mm) and 56% (1590mm) respectively.

20 RE-START the stirrer/agitators for the IGF separator to direct the oil forth to the skimmings compartments.

21 ENSURE Level Controllers 43-LIC-501, 43-LIC-511 and 43-LIC-521 for the skimming compartments are on AUTO at the required set points of 2112mm, 2112m and 1220mm respectively.

22 Once the produced water discharged from the IGF separator is at the required specification of 15ppm, confirmed by lab testing, OPEN Shutdown Valve 43-SDV-381 on the produced water disposal line to the overboard caisson. CLOSE 43-SDV-351 to the slop oil or primary reception tank.

Note: If the oil-in-water content monitored by the oil-in-water analyser 43-AZE-355 reaches 15ppm, the water will automatically be directed to the slop tank/reception tank via 43-SDV-351 and overboard discharge will be stopped by closure of 43-SDV-381.

23 RESTART the injection of water clarifier and scale inhibitor on the produced water outlet of LP Separators A and B as required.





PROCEDURE NO 1/003: NORMAL OPERATION

GENERAL OPERATOR ROUTINES (1) MONITOR the overall operation of the Produced Water Treatment System.

(2) The Field Operator should regularly walk the system to visually inspect for leaks, damage and any system abnormality. REPORT any chemical leaks, malfunctions or irregular operating occurrences to the Team Leader as soon as possible.

(3) The Field Operator should regularly liaise with the Control Room Operator so as to cross-check the accuracy of the instrumentation, ie the comparison between the local instrument and the transmitted level in the DCS.

(4) Visually inspect the condition of the system equipment and pipework for corrosion/deterioration including the security of pipe hangers/fittings.

Off-going shift operators are to ensure that the on-coming shift operators are fully briefed as to the status of the plant as detailed in the shift operators’ logbook. The logbook is to contain sufficient detail of the plant status including any deviation from the norm and, in particular, any isolation of protection equipment. Both the off-going and the on-coming shift operators must sign the logbook before responsibility is handed over.

PRODUCED WATER TANK V-4340 The produced water tank normally operates from the DCS without direct operator intervention. However, some operator intervention is required in the field.

(1) Monitor the hydrocarbon level in the produced water tank. Over a period of time, free oil accumulates on the surface of the produced water in the tank and is required to be periodically drained or ‘skimmed’ and subsequently disposed of using the skimming facilities provided. Refer to Part 2 Section 3 Procedure No 3/001 for full details on this operation.

(2) Ensure that the level control system for the produced water tank modulates 43-LV-301A on the clean water outlet line from Produced Water Hydrocyclone S-4340 to maintain the level in the tank.

(3) Monitor the operation of the recycle loop to ensure that the flow and pressure functions are being maintained.

(4) Routinely cross-check the local level instrumentation with the respective level indications on the DCS.




PRODUCED WATER PUMPS P-4340A/B The duty produced water pump normally operates without direct operator intervention.

However, the following running checks should be carried out periodically so as to ensure that the duty produced water pump is within the normal desired parameters.

(1) Check all joints and glands on the pump sets for signs of leakage.

(2) Check the pump set for unusual noise/excessive noise and vibration and compare against the normal running parameters previously logged.

(3) Check the pump mechanical seal for leakage and signs of overheating.

(4) Check the amperage at the MCC for the pump and compare against the normal running amperage previously logged.

(5) Check the oil level in the thrust bearing housing and top-up as necessary.

PRODUCED WATER HYDROCYCLONE V-4340 The hydrocyclone normally operates without direct operator intervention.

(1) Check the flow of produced water through the hydrocyclone to ensure it is within the operating range for the vessel (168.9m3/hr minimum to 728.8m3/hr maximum). If the flow is outside the operating envelope for the hydrocyclone, the oil-in-water content in the clean water outlet will drift out of specification.

(2) Take regular produced water samples from the hydrocyclone to detect any potential fall-off in efficiency. The hydrocyclone is provided with a sample point on the clean water outlet line. There are also sample points on the produced water inlet and reject oil header.

(3) Back-flush the hydrocyclone on a daily basis by closing the oil reject line and opening the back-flush valve for 30 seconds to ensure the oil reject flow orifices remain clear. Refer to Part 2 Section 3 Procedure No 3/002 for full details on this operation.

INDUCED GAS FLOTATION SEPARATOR V-4341 The induced gas flotation separator normally operates without direct operator intervention. However, some operator intervention is required in the field.

(1) Ensure that the level control systems for the induced gas flotation separator modulate 43-LV-502 and 43-LV-512 on the produced water pipework to maintain the levels in the induced gas flotation separator.

(2) Once per shift, check the produced water flowrate (43-FI-321) and the blanket gas flowrates (44-FI-382 and 44-FI-384) to the induced gas flotation separator.

(3) Ensure the stirrer/agitator provided for each of the four compartments are operating satisfactorily. Running indication is provided at the DCS for each of the stirrer/agitators.

(4) Monitor the hydrocarbon levels in the skimmings compartments of the induced gas flotation separator. Check that 43-LCV-501, 43-LCV-511 and 43-LCV-521 operate under the level control of 43-LC-501, 43-LC-511 and 43-LC-521 to maintain the required level within the skimmings compartments.

(5) Monitor to ensure that 43-LIC-502 and 512 periodically raise the water levels as programmed to allow the oil to skim off.




SAMPLING OF PRODUCED WATER FOR DISPOSAL OVERBOARD A sample point is located on the clean water outlet line from the induced gas flotation separator, upstream of the overboard disposal facilities, to enable the oil/water separation efficiency to be determined. Once per shift, take a sample of the produced water for discharge overboard. Analyse the sample for oil-in-water content and compare the result with the readings given by Analyser 43-AZE-355.

Sampling must be carried out by approved personnel and to the required standards, while observing all safety regulations.

Ensure that the sample container is clean and completely free of hydrocarbon contamination prior to use. Clean glass bottles with tightly fitting plastic stoppers are essential for sampling produced water.

Flushing prior to sampling is vital and must be maintained until the sample temperature is that of the main overboard dump line. This ensures that representative samples are used for the oil-in-water analysis performed on the sample.

If the quality of the overboard water is poor, the efficiency of the upstream induced gas flotation separator and produced water hydrocyclone should be investigated.





PROCEDURE NO 1/004: PLANNED SHUTDOWN



INTRODUCTION This procedure provides a safe and efficient means of shutting down the Produced Water Treatment System.

It is assumed that the Produced Water Treatment System has been running normally and is to be shut down as part of a planned process shutdown.

PRECONDITIONS

Supporting Drawings The Shutdown Procedure makes use of the following P&IDs:

• BON-AME-3PP-B-21443-001-C06

• BON-AME-3PP-B-21443-002-C06

• BON-AME-3PP-B-21443-003-C06

• BON-AME-3GN-B-21448-001-C06

Interface Systems Before the Produced Water Treatment System can be shut down, the following systems are required to be operational:





• Instrument Utility and Air System. Refer to POPM Volume 25 (OPRM-2003-0325)

• Power Generation and Distribution System. Refer to POPM Volume 30 (OPRM-2003-0330)




Pre-requisites

• No work permits are in force which will prohibit the shutdown of the Produced Water System

• Toolbox talks have been held with all directly and indirectly concerned parties outlining the workscope and procedure




PROCEDURE

Step Action

1 CONFIRM that all oil production has ceased.

2 RESET the oil/water interface level controllers for the LP separators and bulk oil treater to MANUAL and progressively CLOSE the produced water level control valves. This stops the flow of produced water from the Oil Separation and Treatment System to the produced water tank.

3 As the oil separation is shut down, ENSURE that 43-PIC-336 opens 43-FCV-321 from the hydrocyclone clean water outlet to the produced water tank, to put the Produced Water Treatment System on full recycle.

4 SELECT the standby produced water pump to OFF then STOP duty Produced Water Pump P-4340A or B.

5 Once the flow of produced water to the tank has stopped, CLOSE the isolation valve in the oil reject line from the produced water hydrocyclone to the oil reject header.

WHEN TAKING THE HYDROCYCLONE OFFLINE, ALWAYS CLOSE THE REJECT VALVES FIRST TO MINIMISE THE POSSIBILITY OF

REJECT BLOCKAGE.

6 CLOSE the isolation valve on the produced water inlet to the hydrocyclone.

7 CLOSE the isolation valve on the clean water outlet from the hydrocyclone.

8 STOP the agitators for each of the four cells inside the vessel.

9 On shutting down the upstream produced water hydrocyclone, ENSURE 43-LCV-522 on the induced gas flotation separator clean water outlet closes as the level falls below 43-LIC-522 set point. Unless intrusive maintenance is to be carried out, the induced gas flotation separator remains in this state until the Produced Water System is started up.

10 CLOSE Shutdown Valve 43-SDV-381 on the produced water disposal line from the induced gas flotation separator to the overboard header. Also ENSURE Shutdown Valve 43-SDV-351 on the produced water disposal line to the slop oil or primary reception tank is closed.

11 DRAIN any surface oil from the produced water tank as described in Part 2 Section 3 Procedure No 3/001. If all the oil has not been drained off before the level is at Nozzle 6B, continue draining via Nozzle 6C.

12 The planned shutdown is now complete. The next steps will depend on the required maintenance to be performed on the Produced Water Treatment System. If maintenance work is to be carried out further isolation can be implemented as required under the Permit to Work System.





PROCEDURE NO 1/005: PROCESS AND EMERGENCY SHUTDOWN



INTRODUCTION Process and emergency shutdowns for the Produced Water Treatment Systems are initiated by intertrip from the ESR System and by activation of one or more of the various SSDS trips, which are clearly indicated on the Cause and Effect Charts.

Supporting Drawings The process and emergency shutdowns pertinent to the Produced Water System are shown on the following Bonga Cause and Effect Charts:

• BON-AME-3GN-B-25082-004 C02 Sheet 1 of 1

• BON-AME-3GN-B-25082-012 A01 Sheet 1 of 1

The cause and effect logic attached to each specific trip is illustrated in detail in the Cause and Effect Chart.

SHUTDOWN HIERARCHY The process and emergency shutdown hierarchy designed for the FPSO is based on a cascade system, the highest level of shutdown being ESR 3 (Total FPSO Shutdown). A shutdown initiated at any particular level automatically initiates all shutdowns associated with lower levels, ie an ESR 3 shutdown automatically triggers shutdown actions associated with ESR 2, ESR 1 and SSDS trip levels.

A brief explanation of the various FPSO shutdown levels is given below:

ESR 3 Total isolation of the FPSO from external sources of hydrocarbons, shutdown and blowdown of all process non-essential utility systems, including subsea shutdown and Surface Controlled Subsea Safety Valve (SCSSV) closure followed by depressurising of hydraulic supplies and electrical isolation.

An ESR 3 shutdown is initiated by activation of the following devices:

• Manual pushbuttons located at the Helideck

• Manual pushbuttons located at the Lifeboat Stations

• Manual pushbuttons located in the CCR




ESR 2 Shutdown of all process systems, including subsea production (not closure of SCSSVs) followed by depressurising of LP hydraulic supplies. The utilities supplied from the emergency and essential generators remain operational but the main power generator turbines changeover from gas to liquid fuel.


• ESR 3 shutdown

• ESR 2 manual pushbuttons

• Manual pushbuttons located in the CCR

• Confirmed fire in a hazardous area

• Confirmed gas in a process area, subsea module or hull

ESR 1

Shutdown of all process systems along with the closure of the FPSO boarding valves and subsea production (not closure of SCSSVs) followed by closure of the oil production, water injection and gas lift riser valves and venting of all SDV air supply manifolds.


• ESR 3 shutdown

• ESR 2 shutdown

• Manual pushbutton located in the CCR

• Confirmed fire in equipment space, MCC or Hull

• Any blowdown valve failing open

• Total loss of main power generation

• Failure of the SSDS System

SSDS

Shutdown of individual items of equipment, ie rotating machine or process equipment. A unit shutdown does not impair the safe operation of the remainder of the process.

An SSDS shutdown is initiated by activation of the following devices:

• ESR 3 shutdown

• ESR 2 shutdown

• ESR 1 shutdown

• Manual pushbutton located in the CCR

• PSD or USD trips

The cause and effect logic attached to each specific trip is illustrated in detail in the Cause and Effect Charts listed in the Supporting Drawings at the beginning of this procedure.






Manual Emergency Shutdown An emergency shutdown of the drive motors for the produced water pumps and the IGF separator stirrer/agitators can be initiated from the following locations:

• The DCS

• The stop button at the MCC starter

• The emergency stop pushbutton adjacent to the respective pump, stirrer/agitator

There are no remotely operated emergency stop facilities provided for the remainder of the facilities in the Produced Water Treatment System.

Refer to the Procedure No 1/004 for details of the planned shutdown of the Produced Treatment Water System.




Part 2 Section 2 Equipment Operating Procedures

OPRM-2003-0311 Page 1 of 2 30- April- 2006


Part 2 Section 2 Equipment Operating Procedures

OPRM-2003-0311 Page 2 of 2 30- April- 2006

PREAMBLE There are no Equipment Operating Procedures identified for the Produced Water Treatment System.

Start-up, Shutdown and Normal Operation of the system equipment is provided in Part 2 Section 1.

Procedures for skimming the produced water tank and back-flushing the hydrocylone are given in Part 2 Section 3.




Procedure Number

PRODUCED WATER TREATMENT SUPPLEMENTARY OPERATING PROCEDURES PROCEDURE NO 3/001: PRODUCED WATER TANK SKIMMING PROCEDURE NO 3/002: HYDROCYCLONE BACK-FLUSHING PROCEDURE

Part 2 Section 3 Supplementary Operating Procedures OPRM-2003-0311 Page 1 of 8 30-April-2006



PROCEDURE NO 3/001: PRODUCED WATER TANK SKIMMING



PREAMBLE Although the oil-in-water concentration is reduced to 1000ppm in the upstream LP separators and bulk oil treater, some oil/water separation takes place in Produced Water Tank V-4340.

The degree of separation depends on the performance of the oil separation and treatment facilities and satisfactory clean water outlet quality from the LP separators and bulk oil treater. Over a period of time free oil accumulates at the interface of the produced water tank and is required to be periodically drained or ‘skimmed’ and subsequently disposed of using the skimming facilities provided.

The oil settling out from the produced water is manually skimmed off to the closed drains through 10 internal pipes, with the top one at Nozzle N6A. The skimming frequency depends on various factors including plant upsets etc and is determined by operator experience.

This procedure details the operator actions required to carry out skimming on Produced Water Tank V-4340.

PRECONDITIONS • No Work Permits are in force which will prohibit any part of this procedure

• CHECK Produced Water Tank V-4340 is operating normally and the isolation valves are positioned as indicated in Valve Checklist No 2, Pre-skimming Positions – Produced Water Tank

• All instrument block valves are open

• All produced water tank drain and vent block valves are closed

• The oil collection sump is available for the disposal of skimmed hydrocarbons from the produced water tank




VALVE CHECKLIST NO 2: PRE-SKIMMING POSITIONS: PRODUCED WATER TANK


Produced Water Tank and Pumps Refer to P&ID BON-AME-3PP-B-21443-001-C06

44-BLV-280 Isolation Block Valve for Blanket Gas Supply to Tank upstream of 32-PCV-001

LOCKED OPEN

44-BLV-281 Isolation Block Valve for Blanket Gas Supply to Tank downstream of 32-PCV-001

LOCKED OPEN

43-BLV-233 Isolation Valve on Skim Line at Nozzle N6A CLOSED

43-BLV-238 Isolation Valve on Skim Line at Nozzle N6B CLOSED

43-BLV-234 Isolation Valve on Skim Line at Nozzle N6C CLOSED

43-BLV-239 Isolation Valve on Skim Line at Nozzle N6D CLOSED

43-BLV-235 Isolation Valve on Skim Line at Nozzle N6E CLOSED

43-BLV-240 Isolation Valve on Skim Line at Nozzle N6F CLOSED

43-BLV-236 Isolation Valve on Skim Line at Nozzle N6G CLOSED

43-BLV-241 Isolation Valve on Skim Line at Nozzle N6H CLOSED

43-BLV-237 Isolation Valve on Skim Line at Nozzle N6J CLOSED

43-BLV-242 Isolation Valve on Skim Line at Nozzle N6K CLOSED

43-BLV-242 Isolation Valve on Drain Line at Produced Water outlet from Tank

CLOSED



PROCEDURE

Step Action

OPEN the top skimming valve 43-BLV-233 at Nozzle N6A and OBSERVE any oil/water flow at the local tundish. If there is no flow (or when flow ceases), CLOSE the top skimming valve and proceed to Step 3.

If the flow is constant and mainly water, CHECK Level Controller 43-LIC-301 is operating in the correct mode with the required set point. This indicates that the vessel level is high. Level Controller 43-LIC-301 is normally set on auto at 50% (2743mm) to control the tank level at the centre line.

OPEN the skimming valve, 43-BLV-238 at Nozzle N6B and OBSERVE any oil/water flow at the local tundish. CLOSE the skimming valve when water instead of oil is seen or oil flow ceases. If water is seen, no further drain-off is required. If oil is still present, further draining is required.

If further drain-off is required, OPEN the skimming valve 43-BLV-234 at Nozzle N6C and OBSERVE any oil/water flow at the local tundish. Close the skimming valve when no more oil is seen flowing at the local tundish.

If on opening the skimming valve at Nozzle N6C water is seen flowing at the local tundish close the valve. This indicates that the oil/water interface is between Nozzles N6C and N6B.

DO NOT DRAIN WATER OFF TO REDUCE THE INTERFACE LEVEL ANY

FURTHER. THIS IS TO PREVENT UNNECESSARY QUANTITIES OF PRODUCED WATER ENTERING THE COLLECTION SUMP.

ENSURE all isolation valves on the skimming lines are closed.




PROCEDURE NO 3/002: HYDROCYCLONE BACK-FLUSHING PROCEDURE



PREAMBLE Internal blockage of a hydrocyclone may occur in the small oil reject stream orifices. There is a greater chance of blockage occurring if the hydrocyclone has been shutdown for a period of time.

Blockages in the oil reject orifices are identified by:

• Increased oil-in-water outlet concentrations over those normally attained

• Lower than normal reject pressure over a range of flowrates

Back-flushing is carried out when oil reject orifice blockages are suspected. Inlet produced water is utilised for back-flushing operations.

However, back-flushing should be routinely carried out at least once per shift.

SCALE FORMATION COULD DEVELOP IN THE HYDROCYCLONE IF RAW

OR POTABLE WATER IS USED.

The produced water hydrocyclone is provided with a 2in backwash line supplied from the produced water inlet header. By opening the block valve on the back-flush line, any debris can be flushed out of the hydrocyclone vessel.

This procedure details the operator actions required to back-flush Produced Water Hydrocyclone S-4340.

PRECONDITIONS • No Work Permits are in force which will prohibit any part of this procedure

• Produced Water Hydrocyclone V-4340 is achieving poor separation efficiency and a blocked oil reject orifice is suspected

• The produced water hydrocyclone is online and the isolation valves are positioned as indicated in Valve Checklist No 6, Back-flushing – Produced Water Hydrocyclone

• All instrument block valves are open

• All produced water hydrocyclone drain and vent block valves are closed




VALVE CHECKLIST NO 3: BACK-FLUSHING: PRODUCED WATER HYDROCYCLONE



43-BLV-227 Isolation Valve on Bypass Line for Produced Water Hydrocyclone S-4340

CLOSED


OPEN

43-BLV-245 Hydrocyclone Vent Valve on 43-RV-323 Relief Line

CLOSED

44-BLV-249 Isolation Valve on 0Oil Reject Line for Hydrocyclone upstream of 43-PDCV-325

OPEN

44-BLV-251 Isolation Valve on Oil Reject Line for Hydrocyclone downstream of 43-PDCV-325

OPEN

43-BLV-246 Hydrocyclone Drain Valve at Nozzle N5A CLOSED

43-BLV-247 Hydrocyclone Drain Valve at Nozzle N5B CLOSED

43-BLV-211 Isolation Valve on Clean Water Outlet from the Hydrocyclone

OPEN

43-BLV-229 Isolation Valve on Produced Water Recycle Line downstream of 43-FCV-321

LOCKED OPEN

43-BLV-213 Isolation Valve on Produced Water Line to Depurator upstream of 43-LCV-301A

OPEN

43-BLV-215 Isolation Valve on Produced Water Line to Depurator downstream of 43-LCV-301A

OPEN

44-GTV-200 Isolation Valve on 43-LCV-301A Bypass Line CLOSED



MANUAL BACKWASH PROCEDURE

Step Action

1 OPEN the isolation valve on the bypass line for Produced Water Hydrocyclone S-4340. This directs the off-spec water from Produced Water Pump P-4340A/B to the induced gas flotation separator.

2 TAKE the affected hydrocyclone offline by slowly closing the isolation valves on the oil reject line, produced water inlet line and clean water outlet line.

WHEN TAKING HYDROCYCLONE PRESSURE VESSELS OFFLINE,

ALWAYS CLOSE THE REJECT VALVE FIRST TO MINIMISE THE POSSIBILITY OF REJECT BLOCKAGE.

3 DEPRESSURISE the produced water hydrocyclone to the collection tanks by OPENING the drain valves for the clean water chamber at Nozzles N5A and N5B.

4 OPEN the backwash inlet valve to the produced water hydrocyclone and maintain the flow for a minimum of 60 seconds. This will create the maximum DP across the reject orifices and drive any debris into the clean water outlet chamber.

5 CLOSE the drain valves for the clean water chamber at Nozzles N5A and N5B.

6 SLOWLY OPEN the clean water outlet valve, produced water inlet valve and after a short time delay the oil reject valve to put the hydrocyclone online.

WHEN STARTING HYDROCYLONE PRESSURE VESSELS ALWAYS

OPEN THE REJECT VALVE LAST TO MINIMISE THE POSSIBILITY OF REJECT BLOCKAGE.

7 SLOWLY CLOSE the isolation valve on the bypass line for Produced Water Hydrocyclone S-4340 to divert all the produced water flow through the hydrocyclone.

8 ALLOW conditions to settle then check the clean water is of the required quality, ie an oil-in-water content of 40ppm or lower. Carry out an analysis of the clean outlet water to gauge the success of the backwashing.

9 If the water outlet quality is still poor then backwashing the hydrocarbon has not been successful. The backwash procedure may be repeated if the first attempt is unsuccessful. The hydrocyclone vessel may require to be positively isolated, flushed, drained and depressurised to allow further investigation.



AUTOMATED BACKWASH PROCEDURE

Step Action

1 SELECT Backwash Sequence.

2 CONFIRM backwash time and delay are set to the required value (adjustable between 20 and 60 seconds).

3 SELECT ‘MANUAL BACKWASH’.

4 SELECT ‘MANUAL START’.

5 The sequence will then perform the following actions:

• 43-PDCV-325 will close

• 43-XV-324 will open

WHEN TAKING HYDROCYCLONE PRESSURE VESSELS OFFLINE,

ALWAYS CLOSE THE REJECT VALVE FIRST TO MINIMISE THE POSSIBILITY OF REJECT BLOCKAGE.

6 At completion of the backwash, the sequence will:

• CLOSE 43-XV-324

• RELEASE 43-PDRC-325 to control by set point prior to backwash

7 ALLOW conditions to settle then check the clean water is of the required quality, ie an oil-in-water content of 40ppm or lower. Carry out an analysis of the clean outlet water to gauge the success of the backwashing.

8 If the water outlet quality is still poor then backwashing the hydrocarbon has not been successful. The backwash procedure may be repeated if the first attempt is unsuccessful. The hydrocyclone vessel may require to be positively isolated, flushed, drained and depressurised to allow further investigation.

WHEN STARTING HYDROCYLONE PRESSURE VESSELS ALWAYS

OPEN THE REJECT VALVE LAST TO MINIMISE THE POSSIBILITY OF REJECT BLOCKAGE.

9 SELECT ‘AUTO BACKWASH’ to allow the sequence to be automatically initiated at the times entered.


v11 produced water

Documents

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procedures volume

incinerator volume

ess volume

telecommunications volume

export system volume

seawater system volume

drainage systems volume