cats technical brochure

CATS – Technical Brochure

www.catspipeline.com

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List of abbreviationsused in this document

Table of Contents

BSC ........................................................British Safety Council

CATS ......................................................Central Area Transmission System

CP...........................................................Cathodic Protection

DCS........................................................Distributed Control System

EBB ........................................................Electronic Bulletin Board

ESD ........................................................Emergency Shutdown

ESDV ......................................................Emergency Shutdown Valve

Ex ...........................................................Export route

H2S ........................................................Hydrogen Sulphide

HAZOP ...................................................Hazard and Operability Study

Hg...........................................................Mercury

HIPPS .....................................................High Integrity Pressure Protection System

HP ..........................................................High Pressure

JT............................................................Joule Thompson

MAEL......................................................Minimum Allowable Energy Level

MAOP.....................................................Maximum Allowable Operating Pressure

MCMD ....................................................Million cubic metres a day

NGLs ......................................................Natural Gas Liquids

NTS ........................................................National Transmission System

OIM.........................................................Offshore Installation Manager

PAA.........................................................Processing Allocation Agreement

PAS.........................................................Processing Allocation System

P1NTS ....................................................Pipeline 1 National Transmission System

PLX .........................................................Platform shutdown

PMS........................................................Pipeline Monitoring System

PPRS ......................................................DTI Petroleum Production Reporting System

PRX.........................................................Process Shutdown

RoSPA ....................................................Royal Society for the Prevention of Accidents

SSIV........................................................Subsea Isolation Valve

SSEL.......................................................Static Stock Energy Level

TAA.........................................................Transportation Allocation Agreement

TAS.........................................................Transport Allocation System

TEG ........................................................Tri-ethylene Glycol

WAN .......................................................Wide Area Network

XAEL.......................................................Maximum Allowable Energy Level

ZnO ........................................................Zinc Oxide

01 Introduction 1.1 Purpose ......................................................................................................02 1.2 CATS System..............................................................................................02 1.3 Teesside Infrastructure ...............................................................................02

02 Health, Safety and the Environment ..............................................................03

03 CATS Future Capacity......................................................................................04

04 Requirements for Entry to CATS System 4.1 Legal and Regulatory Requirements .........................................................05 4.2 Entry Specifications ....................................................................................05 4.3 Measurement and Gas Analysis ................................................................05

05 Riser Platform Technical Data 5.1 Riser Platform Description..........................................................................06 5.2 Access via CATS Riser Platform ................................................................06

06 Pipeline Technical Data 6.1 CATS Pipeline .............................................................................................09 6.2 Access via Sub-sea Tees ...........................................................................12 6.3 Pipeline IT Systems Description.................................................................18

07 CATS Terminal Process Plant Technical Data 7.1 Process Description ...................................................................................22 7.2 Onshore Processing IT Systems Description ............................................27

08 Operational Details8.1 CATS Operational Track Record ................................................................29 8.2 CATS Shutdown and Safety Procedures ...................................................29 8.3 Allocation Principles and Nomination Procedures ....................................30

09 Appendix 1: Specification Data 9.1 Typical Base Entry Specification ................................................................33 9.2 Gas Redelivery Specification .....................................................................34 9.3 Product Redelivery Specifications..............................................................35

10 Appendix 2: New Entrant Check-list ..............................................................37

11 Appendix 3: DCS Data Transfer Signals List.................................................39

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01. Introduction 02. Health, Safety and the Environment

1.1. Purpose

The purpose of this brochure is toprovide technical information on thecapabilities of the Central AreaTransmission System (CATS) toexisting and/or potential customers.

This document provides information on:

© entry and tie-in methods to theCATS System

© system technical details

© system operational details (includingshutdown and emergency response)

This document provides an overview ofthe CATS System and answers commonlyasked questions by Shippers. The datacontained herein should be consideredas typical of the current operation of thesystem. These data should not necessarilybe considered as prescriptive or absoluteas the CATS owners are always preparedto consider options to meet the needs ofnew business.

For further information, please view thecontact details given on the CATS website:www.catspipeline.com

1.2. CATS System

CATS is one of the largest UK North Seanatural gas transportation and processingsystems. Operational since 1993, thesystem can carry over 48 MCMD (1700mmscfd) from a total of 17 different fieldsrepresented by 9 Shipper Groups in the

Central North Sea; J-Block area,Everest/Lomond, Andrew, Armada,SW Seymour, Erskine, ETAP and Banff.

The twin process train terminal(completed in 1998) processes up to34 MCMD (1,200 mmscfd) of gas. Thebalance of the pipeline gas is redeliveredto a third party processor in the vicinityof the CATS Terminal.

CATS is linked directly to the Transcooperated National Transmission System(NTS), which offers unconstrained andlow cost access for onward delivery ofSales Gas.

1.3. Teesside Infrastructure

CATS delivers up to 20% of the UKdemand for gas directly into a major gasand liquids consuming industrial area.Approximately 4 miles along the NTS trunkfeeder line from the CATS terminal, theTransco-owned Cowpen Bewley pressurereduction station provides access to theRegional Transmission System for theTeesside area. Further downstream, CATSgas enters the NTS at Bishop Auckland.

Teesside also has extensive infrastructurefor the distribution of propane, butane andC5+ condensate and the CATS terminal islinked by pipeline to a number of liquidconsumers, including Conoco Norsearefinery, Huntsman, and Vopak.

The CATS System has an outstandingHSE track record. We are committed topursuing BP’s goals of:

© No accidents

© No harm to people

© No damage to the environment

The Terminal has ISO 14001 accreditationand has been presented with severalawards including:

© British Safety Council 5 Star Awardsfor Health and Safety and forEnvironmental performance

© 4 RoSPA Gold Awards

© 6 BSC Swords of Honour forsafety excellence

© Tees Valley Business Awards 2003 -Environmental Award Winner

© IChemE (Institution of ChemicalEngineers) Environmental Award2004 (Commended)

© Partners in Health (North Tees PublicHealth Dept) Certificate of Commendation

The Terminal is accredited by the “Investor inPeople” scheme. The CATS Operator intendsto build on the high standards achieved sofar to deliver continuous improvement.

The workforce is committed to safe workingand all levels of the organisation are trainedto carry our Advanced Safety Auditing,which involves safety conversations withpersonnel working at the site and results inimproved working methods andconditions. The workforce is committed tothe principle that “Nothing is so importantthat it cannot be done safely”.

Throughout the life of the CATS Terminal,including construction and operation,

reducing our environmental impact andmaintaining close links with the localcommunity have been major considerations.Various measures have been establishedto work towards the overall goal of nodamage to the environment.

The use of reedbeds to treat wastewater atthe Terminal ensures that discharged water isalways of a better quality than that requiredby the existing consent levels. Recentwork by a PhD student from DurhamUniversity, sponsored by the terminal, hasquantified the reedbeds’ performance anddemonstrated an increase in biodiversityin bird and aquatic insect life.

A Biodiversity Action Plan is beingimplemented at the Terminal. Frequentevents and projects are undertaken inpartnership with local schools and wildlifegroups to provide education andencouragement of biodiversity.

An impressive performance has beenmaintained in reducing the terminal’senvironmental discharges and activelyminimising waste. For example:

© CO2 emissions were furtherreduced ahead of target

© Liquid effluent wasreduced significantly

© Solid and liquid wasterecycling rates are increasing

© A major programme to improve solidwaste reduction, segregation andrecycling has been implemented

A significant waste stream at the Terminalis spent H2S adsorbent. This is recycled torecover both metals and sulphur in anenvironmentally acceptable manner.

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03. CATS Future Capacity 04. Requirements for Entryto CATS System

CATS maintain a ullage profile, and thefirst five years of this profile is shown onthe CATS website: www.catspipeline.com.

The CATS Owners are currently marketingullage in the CATS system. We anticipatemeeting the demand for new business fromwithin the existing system capacity levels.

Additionally, the CATS Owners can offerexpansion options, if needed, rangingfrom a minor debottleneck to fullexpansion. The CATS Owners wouldbe pleased to discuss any specificrequirements in more detail.

The CATS Owners can offer a varietyof services, including Transportation,Processing, Contaminant Removal,Redelivery of gas and NGLS or anycombination as required by the Shipper.

The CATS Owners can offer entry to thenew Shipper at either the Riser Platform orat one of three sub-sea tees (T1, T2, T5)along the length of the subsea pipeline.The specific technical requirements forentry at these points are included later inthis document and this section providesinformation on the additional requirementsthat have to be met.

Tees T3, T4 and T6 are currently reservedexclusively by another company, Teesside

Gas Transportation Ltd. Please contact theCATS Operator for more information if youwish to access the CATS System throughone of these subsea tees.

An example of the ‘New Entrant Co-ordination Check sheet’ is supplied(Appendix 2) to demonstrate the rangeand extent of activities that are managedduring the tie-in of a new Shipper to CATS.

4.1. Legal and Regulatory Requirements

Prior to entry works commencing, allappropriate Regulatory, HSE and legal

requirements must be met. The minimumrequirements are summarised in thefollowing table.

4.2. Entry Specifications

A typical entry specification for CATS isprovided in Section 9.1. Typical Base EntrySpecification. To maintain CATS overallintegrity, Shippers are expected to complywith the base specification, however theremay be scope for accepting variance tothe entry specification. This will be innegotiation with CATS and should behighlighted at the earliest stage.

4.3. Measurement and Gas Analysis

All measurement and gas analysissystems should be designed andoperated in accordance with theCATS Measurement Manual(Schedule III of the TAA).

Regulatory

DTI Works Authorisation for the installation. This will

include all associated consents and permits, both

for the new third party pipeline and any agreed

modifications to the CATS system issued by the

HSE and others.

u Compliance with BS8010 design and construction

requirements, or equivalent (e.g.DNV 2000).

u Compliance with all other BP requirements pertaining

to the safety of construction operations on the

CATS pipeline and other associated CATS assets.

Legal

Transportation and Processing Agreement

with CATS Owners which includes:

u the Allocation Agreement(s) for Processing

and/or Transportation, and

u the CATS Users Liability Agreement,

u the Cross Indemnity Deed and

u the Engineering Services Agreement with

CATS Owners

05. Riser Platform Technical Data

5.1. Riser Platform Description

The CATS riser platform is a NormallyUnmanned Installation, bridge linked tothe North Everest platform which providesit with power and ancillary services.It stands in 88 metres of water andhas 6 unused spare slots toaccommodate new risers.

5.2. Access via CATS Riser Platform

New risers can be added to/oraccommodated by the Riser Platform butthe number will vary according to size.CATS is able to accommodate changes tothe conceptual layout shown in Figure 1provided they are structurally compatible.

Approaches to the Riser platform areavailable but are subject to approval bythe CATS Operator in order to ensure

adequate protection procedures are inplace for the CATS System. Such approvalshould be sought as early as possible inthe design process.

5.2.1. ESD and SSIV ValvesFor the protection of the Riser Platformand to meet Safety Case requirements,the following valves are required onincoming lines:

© An Emergency Shutdown (ESD)Valve and maintenance valve onthe incoming riser on the RiserPlatform located on the lowestdeck of the Riser Platform.

© A Sub-sea Isolation Valve (SSIV)with associated control umbilical,located approximately 500 metresfrom the Riser Platform may alsobe required, depending on the sizeof the incoming connection.

CATS can install and maintain theplatform based facilities, should theShipper so request.

Riser: 57º 45 28.93 North

01º 48 13.86 East

UTM: 6,402,548 North

428,821 East

Orientation: Platform North: 33 Degrees

East of True North

Figure 1

7 86

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06. Pipeline Technical Data

6.1. CATS Pipeline

The 36” CATS Pipeline runs from the CATSRiser Platform adjacent to the North Everestfield platform to a landfall at Coatham Sands,Teesside, approximately 404 kms away.From this point, the line runs via a BeachValve Station containing ESD and isolation/maintenance valves to the Terminal Site atSeal Sands, some 8 kms distant.

The offshore line is trenched from thelandfall out to 19 kms offshore and then

runs on the seabed for the rest of itslength, apart from those locations whereit crosses the Conoco Ekofisk, the ShellFulmar and the Shell Gannet pipelines.In these locations, conventional subseapipeline crossings have been constructed.

In 2005 a crossing by the Langeledpipeline was installed.

The following table provides data on thephysical characteristics of the CATS pipeline:

Installation Date 1992, Commissioned 1993

Nominal Size 36 inches

Pipeline Detail Outside Diameter Wall Thickness

Riser/Spool Piece 925.4 mm 33.9 mm

Sealine 914.4 mm 28.4 mm

Onshore 925.4 mm 33.9 mm

Material API-5L-X65

Sealine External Coating KP 0 to KP 3972 6 mm of reinforced (glass fibre) coal tar enamel and 51 mm of

high density concrete.

KP 397 to KP 404 6 mm of reinforced (glass fibre)coal tar enamel and 76 mm of

high density concrete.

Onshore External Coating 0 m to 43873 6 mm reinforced (glass fibre)coal tar enamel

4387 to 5102 0.5 mm fusion bonded epoxy

5102 to 7843 6 mm reinforced (glass fibre)coal tar enamel

0 m to 657 Low density concrete

3600 to 3900 Low density concrete

7518 to 7818 Low density concrete

Internal Coating 65 _m COPON EP2306

MAOP 179.3 barg (subsea pipeline)125 barg (onshore)

Maximum Entry Pressure 172.3 bar(g)

Design Life 40 years

Figure 2 provides an offshore schematicof the CATS system

All gas in CATS is transported as DensePhase ‘rich’ gas with a typical

hydrocarbon dewpoint specification of -2˚Cat 103.4 bar(g). The maximum entrypressure is 172.3 bar(g) and the terminalarrival pressure is controlled within arange of 105 to125 bar(g).

2. As measured from theRiser Platform to shore.

3. As measured from theCATS terminal.

ExistingInlet

Facilities

H2SRemoval

InletMetering

600 MMSCFD

600 MMSCFD

Dew PointControl

Dew PointLiquidsProductTreating

Dew PointLiquids

Metering

Gas TreatingTrain 1JT Plant

Gas TreatingTrain 2

Expander/Compressor

Train 2Fractionation

Facilities

3rd PartyProcessor

Train 1Fractionation

Facilities

Common

Export

Metering

BG/NTSGas fromOffshore C3 Phillips

C4 Phillips

C5 + ICINorth TeesC5 +Tees Storage

MercuryRemoval

T4 PROTECTIONSTRUCTURE EXISTING MANUAL

CHECK VALVE36”x24”TEE

20”x8” TEE

30 - 40m

TIE IN SPOOL

10 - 15m

TO TEESIDE

CATS 36” PIPELINE

(EXISTING)

24” PIGGABLE (SPHERE) TEE

8“ MANUALBALL VALVES

24” MANUALBALL VALVES

24” MANUALBALL VALVES

CATS 36” PipelineCapacity in excess of 1.7 BCFD

Completed April 1993

Seal Sands Terminal

Seal SandsTerminal

CATS TerminalGas Processing Facilities

Typical Subsea Tie-in

ProtectionStructure

TEESSIDE

ETAP oil toForties Pipeline System

TranscoNTS Link

Third PartyProcessor

Condensate toHuntsmanNorth Tees

Condensate toVopak

Propane Butaneto ConocoPhillips,

Norsea

HuntsmanNorth Tees

A178

TeesStorage

Northern GasProcessing Ltd

BP (CATS)

ConocoPhillips

Oil Terminal

BeachValve

Station

CATS GasPipeline 36”255 miles

TranscoNational

TransmissionSystem

Tunnel

River Tees

SealSands

BT Mormond Hill

Land line

TROPO toEverest/Lomond

Satellite linkto Andrew

Satellite linkto J-Block

Everest, LomondArmada & Erskine

condensate to FortiesPipeline System

Andrew oil toForties Pipeline System

To Forties Pipeline System

NORPIPETo Teesside

20”

16”

20”10”

24”

6”

T6

T4T3

T2

T1

T5

14”

16”

8”

8”20”

J-BlockCondensateto NORPIPE

Lomond

Erskine

Andrew Platform:AndrewCyrusFarragon

ETAP:Heron ClusterMarnockMonanMacharMungoMirrenMadoes

Armada Platform:ArmadaMariaSeymour

J-Block:JoanneJudyJade

Banff

FPSO

EverestCATS Riser

Platform

BP Aberdeen

ConocoPhillipsAberdeen

TEESSIDE CATS(Terminal and

Processing Plant)

CATS Interfaces:TelecomsMetering DataPipelines



CATS Interfaces:Reception Facilitieson RiserMetering DataTelecoms

Gas

CondensateMulti-Phase

CATS PipelineSystem SchematicFigure 2

10 11

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06. Pipeline Technical Data (cont.)

6.2. Access via Sub-sea Tees

Figure 3 provides a simplified sketch ofCATS Tee 1 (Andrew Connection). Othertees in the CATS system are similar.

The CATS Pipeline has six sub-sea teesand the CATS Owners can offer a flangedentry point via three of these tees, T1, T2and T5. Figure 4 provides a detailed

summary of all of the CATS Tees andpipeline infrastructure.

The sub-sea tees use a double block andbleed assembly which allow a third partytie-in to proceed without interruption to theCATS pipeline normal operations.

6.2.1. Design and Configurationof Tie-in Facilities

The following criteria must be allowedfor in the tie-in design:

01 All design work shall allow for theCATS pipeline being fully pressurisedand operational (up to the line’s MAOPof 179.3 bar(g)) at all times, during allphases of the work. Notwithstandingthis requirement, the design of thespur line shall also allow for controlledor emergency shutdown anddepressurisation of the CATS pipeline.

02 The entire tie-in design andinstallation procedures aresubject to formal approval by theCATS Operator, prior to thecommencement of any work.

03 A suitable corrosion protection system(coating and cathodic protection (CP))must be in place to protect all aspectsof the tie-in and the associatedprotective structures. The CP of the tie-in facilities must be adequate to ensurethat there is no additional current drainon the CATS CP system. Shieldingeffects must be accounted for.

04 Facilities for the pigging of the spurline must be included in the design.There is no facility for pigging the spurline into the CATS line and thereforeallowance should be made for sub-sea pig recovery.

05 Tees T1, T2, and T5 are currently in useand connection would be effected viathe extension flange at each tee.

Tee No.

T1

T2

T5

Flange Size

D24 (610 mm)

20 (508 mm)

20 (508 mm)

Easting

01º 43’ 33.21” E

01º 28’ 12.39” E

01º 12 13 E

Northing

57º 42’ 42.09” N

57º 22’ 1.08” N

57º 01 47 N

13 14

15

06 The new Shipper is required toreplicate the entry flange connectionon a ‘use-and-replace’ basis. It shouldbe noted that the CATS pipeline wasoriginally designed for sour service witha hydrogen sulphide content of 1500ppmv. Any entry facilities provided forfuture tie-in by others must includethis specification.

07 A sub-sea check valve is required onevery new spur line connection toprevent the loss of the CATS pipelineinventory should an incident occur inthird party infrastructure.

08 Expansion spool pieces shall bedesigned to ensure that no stressesare passed onto the CATS pipeline orassociated protection structures.

09 The design criteria for the spur line shallbe consistent with that of the main CATSpipeline. This information is availableon request from the CATS Operator.

10 All tie-in facilities shall be protectedagainst fishing, or other impactdamage, in accordance with standardindustry practice. Particular reference ismade to the traffic of fishing vessels inthe vicinity of the CATS pipeline. Anyprotecting structure shall remain entirelyseparate from that protecting the CATSinfrastructure and shall impose no loador other influence upon it.

6.2.2. Requirements for Tie-InInstallation activities

01 All aspects of the tie-in installation shallallow for the CATS pipeline remainingfully operational and pressurised (up tothe line’s MAOP of 179.3 bar(g)) at alltimes during all phases of the work.

02 All procedures covering theinstallation work and the identity ofthe contractor(s) proposed to be usedin its execution shall be submitted tothe CATS Operator for their formalapproval before any offshore workcommences. Representatives of theCATS Operator are available fortechnical consultation to assist thisprocess. The CATS Operator willrequire offshore representation toassure both the continued integrityof the CATS Asset and propercommunications with the CATSoperations teams.

03 HAZOP procedures are to be carriedout on all the offshore activities,sufficiently ahead of the offshoreprogramme for recommendationsto be incorporated in procedureor design changes. The CATSorganisation can assist in thisprocess and can offer their previousexperience with other tie-in operations.

04 Commissioning procedures shall bedeveloped to ensure that no free waterenters the CATS system prior to start-up. Dewatering procedures are to be

06. Pipeline Technical Data (cont.)

16 17

1918

06. Pipeline Technical Data (cont.) 06. Pipeline Technical Data (cont.)

reviewed and approved by the CATSOperator. Other substances applied forby Shippers will be reviewed by CATS.

05 Prior to tie-in, all spur lines shall be gelcleaned and dried. All gel dischargesare to be at least 30 metres away fromCATS infrastructure. Nothing shall bepassed into the CATS pipeline duringthe tie-in, cleaning, testing orcommissioning operations without prioragreement with the CATS Operator.

06 The integrity of the finalisedassembly shall be establishedthrough hydrostatic leak-testing.The ball valve immediately down-stream of the entry flange shall beused as the blocking medium.

6.2.3. Crossings andProximity Agreements

The Shipper shall also ensure that anycrossing or proximity agreements betweenitself and the CATS Owners have beensigned before the start of any offshore work.

6.3. Pipeline IT Systems Description

6.3.1. GeneralTo enable efficient and reliable operationof CATS, selected data is made availablefor specific control systems. These controlsystems provide the basis of nominationand the allocation of gas supplies, monitorcritical operating parameters, allowoperation of a pipeline leak detectionsystem and also give means to shut ingas supplies in cases such as when off-specification supplies cannot be tolerated.A Wide Area Network (WAN) collects

shipper data and passes it to the followingsystems located at Teesside Terminal.

a) Transportation Allocation System (TAS),which provides means of planning,controlling and recording of shippernominations and gas redeliveries.

b) Pipeline Monitoring System (PMS)provides information regarding pipelineparameters and enables leak detectionof various pipelines. Note: this system isnot the primary means of pipeline leakdetection but provides further back-up.

c) Pipeline Distributed Control System(DCS) allows operators at Teesside toview critical operational data fromshippers. This also provides the meanswhereby a Teesside operator can alsoshut in a shipper should it be required.

The data required to be transferredbetween CATS and the shippers withthe frequency of update is detailed inAppendix 3 – “Data Transfer betweenCATS and Third Party Entrants”.

6.3.2. Transportation Allocation SystemTransportation nomination and allocationprocessing is handled by a systemknown as TAS (the “TransportationAllocation System”). This system isgoverned by the principles stated in theTAA (the “Transportation AllocationAgreement”).The TAS system acceptsnominations at any time and uses thereceipt time and effective time of eachnomination to determine its timeliness.Nominations are aggregated across

buyers and redelivery points and furtherprocessing determines whether firm andredelivery capacities have been exceeded.On an hourly basis, TAS communicateswith the metering and DCS systems toread metered data for the previous hourlyperiod. At a regular frequency allocationwill be run and a statement produced forshippers. Daily and monthly allocationstatements are also produced. OtherTAA provisions are also managed by thesystem e.g. reduction in capacity andsubstitution. Finally, the system producesa Pipeline PPRS return to be sent to theDTI each month.

CATS’ customers have the ability tointerface directly with the TAS by meansof CATS Panthers. This is a secureapplication which allows viewing and/ordownloading of bulletins, allocation dataand statements as well as data entryand/or uploading of nominations and otherdata, such as shipper production shares.In the event that the Panthers service isunavailable, nominations may besubmitted via fax using standard forms.In such an event, allocation statementswill be sent out using fax or e-mail.

Nominations are made in units ofMWh/day and rates may vary at half-hourintervals. A maximum of eight suchvariations is permitted in a gas day.

6.3.3. Pipeline Safety andLeak Detection SystemsThe Pipeline Modelling System (PMS)employs two independent methods ofpipeline integrity monitoring. Method 1,deviation analysis, compares pipelinemodel computed values of pressure andflowrate to measured data supplied by the

pipeline SCADA system. If the modelledvalues deviate from the measured valuesan alarm is given in the terminal controlroom. Method 1 also contains a locationalgorithm, which estimates the location ofthe indicated leak along the pipeline route.Method 2, a pipeline volume balance,compares inventory changes due topressure and temperature changes.Either method can independently alarmthat a potential leak exists.

Actions to be taken when an alarm of apotential leak is given by the PMS willdepend upon the calculated size of theindicated leak and its indicated location.

Large indicated leaks offshore maynecessitate the immediate shutdown(ESD) of all offshore platforms (excludingCATS Riser) while leak verification activitiestake place. Large indicated leaks onshorewill necessitate an immediate ESD of theBVS and offshore, while continuing toevacuate gas through the Terminal.

6.3.4. Telecommunications(Voice and Data)The pipelines associated with theCATS are controlled and monitored bya telemetry system. This utilises thedigital tropospheric (‘tropo’) scattersystem linking the North Everest andthe Lomond platforms to the BT stationon Mormond Hill. Onshore links areprovided by landlines to BP ExplorationAberdeen and the CATS Terminal inTeesside. All platforms are provided withmutual communications access via the‘tropo’ system. In addition North Everestand Lomond are linked by a subsea fibreoptic system.

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06. Pipeline Technical Data (cont.) 06. Pipeline Technical Data (cont.)

Hydrocarbon processing offshore and atthe CATS Terminal are controlled andmonitored by a Distributed ControlSystem (DCS) in each control room.

6.3.5. Pipeline DCS and Data SecurityThe Wide Area Network has primaryconnections at the Lomond, North Everest,Aberdeen and Teesside locations.

Further connections are available forShipper data at either offshore (NorthEverest or Lomond) or onshore locations.The data received at these points isrouted to the Teesside Terminal foronward transmission as required to therelevant control system.

The availability of correct, secure datatransfer is of paramount importance toCATS. Security of data is achieved by theuse of data links that always require bothCATS and the Shipper to be in agreementof which data is exchanged. By this meansit is ensured that CATS only receives therequired data and that this data cannot beinadvertently passed to a third party.

6.3.6. Test and CommissioningAcceptance – DCS CommunicationThe testing and commissioningacceptance for data communicationis usually achieved in four stages.

© Type test

© Works test

© On-site simulation

© Final commissioned data

a) Type TestThis test confirms that the CATS DCS willcommunicate successfully with Shipper’scontrol system. This test would normallybe conducted early within the Shipper’scontrol system build phase.

Participants would normally be:

© CATS personnel

© CATS DCS vendor

© Shipper or Shippers’ representative

© Shipper control system vendor

b) Works TestThis test confirms all signals are beingtransmitted and received correctly andwould be conducted at the ShipperFactory Acceptance Test. Simulated datawould be for this test but all points wouldbe represented. Attendees as for a).

c) On-Site SimulationThis is a repeat of b) but the totalsystem including any data transmissionequipment, for example line-of-sight,telephone links, etc. are all operational.Participants would include:

© Shipper nominatedrepresentative or vendor

© CATS personnel.

Again data is simulated but includes fullend to end checks, for example Shippermetering system through to the CATSinterface point.

d) Final Commissioned DataThis represents the final stage andprovides acceptance to both parties thatactual data is being transmitted andreceived correctly. Acceptance would beprovided by a nominated CATS personand Shipper personnel.

6.3.7. Failure of Control Systems/Loss of Communications6.3.7.1. Failure of Control SystemsIf the failure has not already caused anautomatic shutdown, a manual shutdownmust be initiated followed by blowdown ifthis has not already happened.

If there is an indication of unsafe operatingconditions or control cannot be exercisedeffectively, then the pipeline must be shutdown. Personnel on the Shipper’s platformshall confirm shutdown actions have takenplace. The Shipper’s OIM will determinethe necessity for closure of manual valvesas an added precaution.

Status reports shall be provided toCATS Terminal control room and BPExploration Aberdeen.

6.3.7.2. Loss of CommunicationsIn the event of a total loss ofcommunications (‘total’ meaning loss

of both data and voice communications)between the Shipper’s platform and CATSControl, Teesside, a production shutdownwill automatically occur after 30 minutes.However, if verbal communications arerestored within the 30 minute period, thenthe following should be implemented:

01 Operating conditions should bemonitored at each location and ifany abnormalities or unsafe conditionsare detected then the pipeline shall beshut down.

02 If it is suspected that a major incidenthas occurred, even if the Shipper’splatform has not been shut downautomatically, then erring on the sideof caution, the Shipper’s platform shallbe shut down.

03 Following a ‘total’ communicationsfailure and consequently, verbalcommunication has been restoredwithin the 30 minute period, thenproduction from the installation maycontinue up to a period of 3 hours.If ‘total’ communication links havenot been restored after this 3 hourperiod, then a shutdown of thefacility will be initiated.

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07. CATS Terminal ProcessPlant Technical Data

7.1. Process Description

The overall purpose of the CATS Terminalis to process gas and NGLs from thepipeline to enable it to meet the exportspecifications. This involves severaldiscrete stages and sub processes whichare described in some detail below.

7.1.1. ReceptionGas direct from the offshore pipelinearrives at the plant inlet at between 100and 120bar(g) with a temperature between1 and 5oC, depending on currentconditions. These conditions coupled withthe composition of the gas ensure that itis single phase flow in to the terminal byholding the gas in the dense phase.Here it behaves like a gas with some ofthe properties of a liquid due to its density.The reception facilities have a capacity inexcess of 50 MCMD (1700 mmscfd).

The dense phase gas passes throughthe main 36” emergency shut down valve(ESDV) and its adjacent maintenancevalve before it enters the receptionfacilities proper. The gas can then bepassed through a pig receiver thoughthis is bypassed unless pipeline inspectionactivity is taking place. Next are the twinslug catchers which are designed toremove any liquid arriving with the gas.This is never the case during normaloperation because of dense phaseoperation. However the slug catchers areprovided with level indication and meteredliquid export facilities in case an upsetoccurs or an alternative mode of operationis selected in the future.

The slug catchers are followed by twinfilter/coalescer units designed to removegross solids from the gas down to10 microns.

Following this the gas is ‘sweetened’by removing excess hydrogen sulphide(H2S). This is achieved by passing thegas through large, absorbent pellet (ZnO)beds which convert H2S to water andretain the sulphur. The sweetening or‘gas treating’ process is controlled toensure the outlet H2S specification isnot exceeded by using a bypass system.Mercury is removed from all the gaspassing through treatment by eitherdedicated absorbent beds in the bypassroute or by the H2S absorbent pellets.The final part of the reception process isa set of filters to ensure no pellets or dustfrom the gas treatment beds passes anyfurther through the system.

7.1.2. MeteringFollowing treatment in the receptionfacilities the gas flow is split for finalprocessing through two routes. Themajority of the gas, up to 34 MSCMD(1200 mmscfd), passes to the two CATSprocessing trains through Export RouteOne, often abbreviated to Ex1. Theremainder of the gas, up to 18 MSCMD(600 mmscfd), is sent to a neighbouringgas processing facility. Since the offsitefacility has two trains this route is knownas Ex2/3. In order to ensure the split iscorrect and for commercial and fiscalpurposes the gas is accurately meteredthrough two separate systems. Both Ex1and Ex2/3 metering employ banks of

HgREMOVAL

INLET GAS

PIG RECEIVER

TREATERSH S/Hg2

3rd PARTYGAS TO

3rd PARTYGAS TO

WATERTEG/

NTSGAS TO

PROPANE PRODUCTTO CONOCO PHILLIPS

BUTANE PRODUCTTO CONOCO PHILLIPS

NATURAL GASOLINEPRODUCT TO TEES

NATURAL GASOLINEPRODUCT TO HUNTSMAN

BUTANE FROMTRAIN 2

DEPROPANISER

STABILISER

TURBO EXPANDER (TRAIN 1)

NITROGENINJECTION

GAS FROMTRAIN 2

COMPRESSOR

Ex-PIPELINE

JT VALVE (TRAIN 2)

TEG

GAS TO CATS - 1200 MMcfpdPROCESSING GAS HEATER

SLUGCATCHER

FILTER

H SREMOVAL2

PROPANE FROMTRAIN 2

GASDEHYDRATION

GAS TO TRAIN 2

NATURAL GASOLINEFROM TRAIN 2

DEBUTANISER

LTSEPARATOR

INLETSEPARATOR

Ex1 METER

Ex2 METER

Ex3 METER

300MMcfpd

300MMcfpdPROCESSING

PROCESSING

FIGURE 6

M

M

M

M

M

M

M

SLUG CATCHER

HG TREATER

FEEDGASEXCHANGER COMPRESSOR

SUCTION DRUM

REBOILER

REBOILER

REBOILER SURGE DRUM

OVERHEAD DRUM

CONDENSER

CONDENSER

COOLER

OVERHEAD DRUM

H2S/HG TREATER

2625

07. CATS Terminal ProcessPlant Technical Data (cont.)


metering tubes. The flow through the tubesis controlled automatically by a meteringcomputer which measures the flow usinghigh accuracy orifice plates. The gas isalso passed through a chromatograph todetermine its composition.

7.1.3. Gas Processing TrainsCATS has twin gas processing trains,each with a capacity of 18MSCMD (600mmscfd). They are identical in all respectsexcept for the expander-generator facilitiesfitted to train 1.

The metered gas from Ex1 passesthrough the train isolation ESDV and intothe dehydration tower. It is necessary todehydrate the gas to prevent hydrate orice formation later on in the cold sectionsof the plant. This vessel allows the gas tocome into contact with a counter-currentflow of tri-ethylene glycol (TEG) on astructured packing. The gas typicallycontains 20 ppm of water at this stage,including that generated by H2S removal,but this is reduced to less than 2ppm asthe TEG absorbs most of the water.The TEG is circulated in a closed loopthrough a regeneration process topreserve its purity.

The dehydrated gas is then pre-chilledby heat exchange with the cold exportgas in two large shell and tubeexchangers, known as the gas: gasexchangers. This takes the gas down tosub zero temperatures. Further reductionin gas temperature is achieved by theJoule-Thompson effect as its pressure isreduced to 60 bar(g). A bypass line allowsthe temperature to be controlled. Bothtrains are fitted with a JT valve for pressurereduction and train 1 is also equipped with

a turbo-expander generator. This providessufficient electric power to run the train.For maximum liquid recovery (CATSnormal operating mode), temperaturesas low as -33˚C are achieved. Formaximum gas recovery a temperatureof -15˚C is typical.

The cold gas will have produced liquidsand these are separated in the lowtemperature separator vessel. Salesspecification gas leaves the top of thisvessel via a demister while liquids aresent for stabilisation and fractionation.The gas stream is warmed through thegas: gas exchangers and brought up toexport temperature in a sales gas heaterwhich uses the train’s hot oil. Finally thegas is metered again through the P1NTSsystem and exported to the NTS fordistribution by Transco. The CATS terminalhas pressure control facilities as the‘back end’ of the process to allow forfluctuations in NTS pressure.

7.1.4. Liquid Stabilisationand FractionationThe unstable natural gas liquids (NGLs)from the low temperature separator arepassed to the first of a series of threedistillation columns for further processing.The first column, the stabiliser, is designedto remove light components from theNGLs and so a mixed stream ofpredominantly methane and ethane isproduced from the top of the columnas the overhead stream. The column isheated by hot oil applied in a kettle typereboiler at its base and has no overheadcooling or reflux. The overheads arecompressed to export pressure by tworeciprocating compressors and thenjoin the main gas export stream.

There is a facility for nitrogen injection atthe compressors’ suction. This is to modifythe Wobbe Index (burning characteristics)of the gas, if necessary.

Stable NGLs leave the bottom of the firstcolumn for fractionation in two columnswhich operate on the same principle. Thedepropaniser receives the NGLs anddistils propane product as its overheadstream. The column is equipped with finfan coolers for overhead pressure andtemperature control and an overheaddrum. Heat is applied by the reboiler usinghot oil. The column has two propanepumps to feed the product to export andprovide a reflux to maintain purity.

The third and final column, thedebutaniser, takes its feed from thedepropaniser bottom. It produces mixedbutane product as its overhead and apentane plus stream of natural gasoline asthe residual of the stable NGLs. It operatesin a similar fashion to the depropaniser.

The three liquid products of propane,butane and natural gasoline are pumpedto a metering system before export tolocal industry through dedicated pipelines.The propane product can be treated forfurther H2S removal via an absorbent bedif required. The specifications of theproducts are in section 9.3.

7.1.5. UtilitiesThe hydrocarbon processing systemsdescribed above require numerousutilities for their operation:

© Electricity

© Fuel gas

© Hot Oil

© Glycol

© Nitrogen

© Air

Electricity is supplied to the terminal via thenational grid through two 11kV incomers.The major users are the overhead gascompressors. An emergency supply isavailable from an on site diesel generatorand battery back up is provided for allcontrol systems.

Fuel gas is taken from the sales gasstream though pipeline gas or gas fromthe NTS can be used if required. Fuelgas is mainly used by the hot oil systembut it also supplies vessels for pressuremaintenance purposes. The fuel gassystem comprises pressure let downand heaters for the various users.

The Hot Oil system boasts the largestsingle pieces of equipment on each train,the Borne Heaters. Each heater has eightburners to heat a constantly circulatingflow of heating oil around the terminal.The hot oil system has two pumps pertrain and a pressure control system tocompensate for variations in demand.The hot oil heaters can also burn wastegas from the glycol regeneration process.

2827



The glycol system has two positivedisplacement pumps to circulate TEGthrough the contactors on each train.The wet glycol returning from the processis regenerated by a sub-process utilising‘Coldfinger’ technology. Here the glycol isheated to boil off the water and filtered toremove entrained hydrocarbons.

The CATS Terminal has a dedicatednitrogen delivery pipeline. The major useis for sales gas Wobbe correction, thoughthis is not necessary under normaloperation. Each train is equipped with anitrogen compressor to inject in to thegas stream when there is a demand.Lesser uses include seal pressuremaintenance and purging.

The terminal has two electric and onediesel air compressors for controlfunctions and general use around the site.

7.1.6. Safety SystemsThe CATS terminal has several systemsinstalled for safety reasons. It has a firewater ring main supported by two firewater pumps (one diesel) to supplymonitors located strategically around thesite. The pumps are fed by a fire waterpond. The ring main is duplicated andconnected to a neighbouring facility toguarantee availability.

The flare system comprises two flarestacks. The major, HP, flare is provided asa route to dispose of the plant inventorysafely in an emergency. This is achievedvia a phased blow down system whichreduces the plant pressure in sections.The minor flare was installed to dispose ofwaste gas during process upsets as the

HP flare’s configuration does not burnthese streams efficiently.

Gas monitors are fitted throughout the siteto warn and automatically shut down theprocess if a gas leak has occurred.

The terminal uses a High IntegrityPressure Protection System (HIPPS) toprevent over pressure from the offshorepipeline. This uses a voting system andshutdown valves.

7.1.7. Alternate Operating ModeThe processing trains can be adjusted tooperate without producing a propane orbutane product when the need arises.This is achieved by increasing thetemperature of the stabiliser so thesecomponents leave with the export gas.The gas quality is adjusted with nitrogento meet export specification.

This mode is advantageous when theliquid export routes are not available orwhen it is financially sound to export theproducts with the gas. Processingparameters can be adjusted at any timeto vary the amount of liquids produced tosuit demand and market conditions.

7.2. Onshore ProcessingIT System Description

7.2.1. Processing Allocation SystemProcessing nomination and allocationprocessing is handled by the ProcessingAllocation System (PAS). This systemis governed by the principles statedin the PAA (the “Processing AllocationAgreement”). The PAS system acceptsnominations at any time. Although the PAA

has no concept of timely nomination, thePAS generates wet gas nominations forthe Transportation Allocation System(TAS) and passes the receipt time ofthe originating dry gas nomination to theTAS. Nominations are aggregated acrossbuyers and redelivery points and furtherprocessing determines whether firmcapacities have been exceeded. On anhourly basis, PAS communicates with themetering system to read metered data forthe previous hourly period.

At a regular frequency allocation willbe run and a statement produced forshippers. Daily and monthly allocationstatements are also produced. Other PAAprovisions are also managed by thesystem, e.g. reduction in capacity.

CATS’ processing customers also havethe ability to interface directly with the PASby means of the CATS Panthers system,as detailed previously.

7.2.1.1. Distributed ControlSystem and Data SecurityThe onshore gas receipt and processingfacilities are controlled by the Plant DCSsystem which is linked to the offshoreWAN. The Pipeline and Plant DCScommunicate at the Teesside Terminal.

A data transfer system that only allowsthose signals agreed by both systems tobe transmitted is used. When received bythe CATS pipeline control system this datais forwarded as previously described tothe relevant Shippers.

Further plant data as required by theonshore control systems (PMS/TAS/PAS)is communicated directly from the PlantDCS by secure transmission system to the

required control package. The plant control system performs allrequired process control for the Teessideplant and provides any required onshoreallocation of products.

7.2.2.TelecommunicationsThe telecommunications system betweenCATS terminal and either liquids or gascustomers will carry the following:-

01 Data between CATS terminal andthe customer.

02 Provide the possibility of carryingvoice in the form of a hotline orpossibly an inter-PABX connection.

The preferred method of providingTelecommunications between the CATSTerminal and the customer is by FibreOptic Cable. The Fibre Optic Cable will beco-located in the same trench as thepipeline serving the customer.

If the customer is not connected with adirect fibre optic connection then they willbe required to lease a data and voicecircuit from a public telecommunicationcarrier. In this instance the provision of theNTUs, modems and signalling units at theCATS terminal end, associated with theseprivate circuits will be the responsibility ofthe customer. Space and power will bemade available.

The method of connectivity to the CATSNetworks, including voice is to be inaccordance with BP Global WAN designStandards. Since this is a live standardsdocument, additional changes may beforthcoming in the future based on newand changing requirements

3029

08. Operational Details 08. Operational Details (cont.)

8.1. CATS Operational Track Record

01 The CATS system availability since2000 has exceeded 99.5%.

02 The non-intrusive inspectionprogramme in CATS has increasedthe interval between inspection-drivenshutdowns to 10 years.

03 The CATS System can offer flexibilityin redelivery of product.

04 The CATS System has a comprehensiveIntegrity Management Scheme thatensures a 40 year operational life span.

05 The CATS System is responsive toShipper requests. The system isfocused on delivering the flexibilitythat Shippers may need to meettheir nomination requirements.

8.2. CATS Shutdown andSafety Procedures

Incoming gas pipelines to the CATS RiserPlatform are equipped with a topsidesESD valve and (depending on connectionsize) a hydraulically operated SSIV. Themain CATS Pipeline is fitted with a topsideriser ESD and a sub-sea check valve toprevent backflow from the pipeline to apossible topside or riser leak/rupture.

Pipeline shutdowns are initiated by highor low pressures within the pipework ormanifolds. A High Integrity PressureProtection System (HIPPS) is usedwith a ‘2 from 3’ voting system oneither high or low pressures.

The following policy is currently in force.

The topside riser ESD valve is closedin the following cases:

© Low pressure on theincoming line (PXSL)

© Low pressure on theoriginating platform

© Loss of communicationswith the originating platform

© A platform shutdown (PLX)on the originating platform

This would also initiate the closure of thetopside riser ESD on the originating platform.

Higher levels of shutdown (processshutdown -PRX) on the CATS RiserPlatform also initiate closure of thesevalves, i.e.

© High or Low Pressure (PXSH or PXSL)on the outgoing CATS 36” pipeline

© Low pressure (PXSL) at the inlet tothe Onshore terminal.

These alarms initiate the shutdown of allhydrocarbon flow across the Riser Platform.

Confirmed fire or gas alarms on theRiser platform (PLX or ESD2) initiate acomplete platform shutdown, closingall topside valves.

The highest level alarm, a full “ESD”,initiated by push-button closes the sub-sea SSIV on all the incoming gas lines.

8.3. Allocation Principles andNomination Procedures

8.3.1. Allocation PrinciplesCATS Allocation Systems are energybased and work on the principle of ‘StockAccounts’. The Transportation AllocationAgreement (TAA) covers the details ofallocation for all users of the system frominput point (field meters on the platform) toredelivery points (Ex1, Ex2, Ex3) for gas orEx1s, Ex2s, Ex3s for associated NGLs.

The Processing Allocation Agreement(PAA) covers the details of allocation forall users of the CATS plant, from the inputpoint (Ex1) to the redelivery points (NTS,propane, butane, C5+).

Each Shipper delivers gas into aCATS Stock Account, the accountbeing managed by the Stock AccountRepresentative, who is usually the platformoperator. At 19:00 hours each day, theStock Account Representative requeststhe amount of gas required to be deliveredby CATS for the following Gas Day - a drygas requirement if it is to the NTS or a wetgas requirement if it is for delivery to eitherEx2 or Ex3. The dry gas figures areadjusted by CATS and each platform isinformed of the volume of gas it needs todeliver into CATS to achieve its nomination.

The CATS allocation systems operate inenergy terms. The volume of the pipeline,including all the spur lines, at the minimumonshore safe operating pressure of 105bar is known. Dividing this volume inproportion to the Firm Booked Capacitiesof the Shippers, as detailed in theTAA, determines their Static Volumerequirements. On converting to energy

this gives the Static Stock EnergyLevel (SSEL) below which no gas willbe redelivered.

On the basis of the known totalnomination for the next allocationperiod, the CATS Operator determinesthe minimum volume required to be putin at the platforms to be able to meetthe nomination. This figure is dividedup in proportion to each Stock Account’snomination, converted to energy andreported as the Minimum AllowableEnergy Level (MAEL), required to beinput by that Stock Account to achievethe nomination.

CATS also determine the maximumvolume that all Shippers can put intothe system, based on nominations andmaximum pressures. This is divided upin proportion to the firm stock accountcapacity for each stock account,converted to energy and is reportedas the Maximum Allowable EnergyLevel (XAEL) for that Stock Account.

The Shipper groups manage their ownstock accounts between their MAEL andXAEL levels. It is possible, for example,for a platform to export well in excess oftheir nomination requirements to buildup ‘stock’ in the event that they areexpecting lower production in the futurefor maintenance purposes and will utilisetheir stock to fulfil the nomination.

On a given day a platform will export gas,which is converted to energy using livedensity and gross calorific value data.From this gross figure background fueland contaminant fuel are deducted.

3231

08. Operational Details (cont.) 08. Operational Details (cont.)

Background fuel is the fuel used at theonshore terminal prior to the redeliverypoints and the riser and onshore flaresand is divided up proportionally.Contaminant fuel is the fuel used to purgethe H2S and Hg Removal beds duringcatalyst change-out and is calculated ona‘polluter pays’ basis. The CATS AllocationAgreement provides for substitution,whereby gas is borrowed and lent to aSubstitution pool. Substitution “In” or “Out”gas is added or subtracted from the grossfigure at this point to give the net input tothe Stock Account.

The gas is then redelivered through the3 redelivery points and the redeliveredquantities are calculated at the end ofeach allocation period. Within the TAA,Schedule III (The CATS MeasurementManual) details CATS requirements forplatform metering systems. In this sectionthe requirements for electronic meteringdata required to be transmitted by theplatform to CATS are detailed. Thesedata enable CATS to perform allocation(i.e. hourly compositional data, volumes,energies, masses, cumulative data, dailydata, historical data). The allocationsystem determines (from the input data,the nomination requested and the currentStock Account status of each account)how much gas is attributed. In the eventthat there is sufficient gas delivered intothe pipeline then all nominations wouldbe met.

The CATS Operator is currently operatinga two (2) hourly allocation period.

If, however, there was to be a shortageof gas, determining which account isshortfalled is based upon the attribution

rules within the agreement. It is ultimatelydependent upon whether each account’snomination was ‘timely’, had enoughpipeline capacity rights to transport thequantity of gas, enough redeliverycapacity at the redelivery point or enoughenergy in their stock account such that itdid not drop below the MAEL figure - thefigure required to ensure that thenomination is met.

All inputs to and outputs from the Allocationsystem are posted onto the CATS Pantherssystem. Each Stock Account Representativehas access to data pertaining to just theirown Stock Accounts.

8.3.2. Forecast andNomination ProceduresNomination procedures are set out inthe CATS Transportation AllocationAgreement and the CATS ProcessingAllocation Agreement (TAA/PAA). Therefollows a summary of these procedures.

Weekly Forecast: (all values to bequoted in megawatt hours)

Each Friday by 18:00 HrsWeek - 2 Days

The Stock Account Representative willsend a notice to the CATS GasAdministrator detailing the projectedquantity of energy required to beRedelivered into the National TransmissionSystem (NTS) at the Redelivery Point eachDay in the forthcoming week.

Daily nominations: (all nominations tobe quoted in megawatt hours)

by 19:00 HrsDay – 1

Each Day the Stock AccountRepresentative will send the CATSGas Administrator a Daily nominationof energy required to be Redelivered intothe relevant Redelivery Point on thefollowing Day. If no nomination is giventhen the last notified nomination rate willcontinue to apply.

The notice will provide informationas detailed in TAA Clause 7.


Each Day the CATS Gas Administratorwill issue a notice to the Stock AccountRepresentative detailing the calculatedamount of gas estimated to be requiredfrom the Stock Account (Wet GasNomination) for processing in order to

meet the Redelivery nominated by theCATS Field Operator.


Each Day the CATS Field Operator willissue to the CATS Gas Administratordetails of the volume of wet gas whichis intended to be delivered into CATSSystem during the Day.

Changes to nominations: (allnominations to be quoted inmegawatt hours)

DailyPrior and within Day

The Stock Account Representativemay issue notices, to the CATS GasAdministrator changing the dailynominations of energy previouslymade (Renomination).

Renominations are subject to timelynotification periods as follows:

8.3.3. Cutback ProcedureIn the event of a capacity restriction in theCATS System, Shippers are allocated a

share of the restricted capacity onthe basis of pro-ration of their firmcapacity booking.

% change per firmStock Account Capacity

More than 50% change

>25% to 50%

>10% to 25%

0% to 10%

INCREASE minimum notice period

24 hours

12 hours

6 hours

1 hour

DECREASE minimum notice period

8 hours

6 hours

4 hours

1 hour

3433

09. Appendix 1: Specification Data 09. Appendix 1: Specification Data (cont.)

Below are a typical gas entry specificationand the product specifications whichappear in the CATS TransportationAgreement. These specifications may varyat the discretion of the CATS Operator. Thecurrent specifications are displayed on theCATS website: www.catspipeline.com

9.1. Typical Base Entry Specification

In order to comply with the EntrySpecification, all Shipper Gas shallcomply at the Delivery Point, with thefollowing requirements:

01 be delivered at the Delivery Point ingaseous single phase only andcommercially free from objectionableodours and from materials and dusts orother solid or fluid matter which mightcause injury to or interference with theproper operation of the CATS Systemand/or which could affect themerchantability of CATS Gas or CATSProduct. For the avoidance of doubt,such materials shall include but not belimited to, lead, radioactive materials,waxes, gums, and gum formingconstituents, foaming agents andexcessive solids;

02 have a hydrocarbon dew point which atall pressures in excess of 10,340 kPaGauge does not exceed -2 deg C;

03 have a maximum water content to bethe lesser of:

© 15 Kg per million standardcubic metres; or

© that content equivalent to awater dew point at 7,500 kPaGauge of -26 deg C;

04 have a maximum hydrogensulphide content of 3.0 ppmv;

05 have a maximum methyl + ethylmercaptan sulphur content of 0.5 ppmv;and have a maximum total mercaptansulphur content of 3.1 ppmv;

06 have a maximum carbonylsulphide content of 1.0 ppmv;

07 have a maximum total sulphurcontent of 14.4 ppmv measuredas hydrogen sulphide;

08 have a maximum carbondioxide content of 2.9 mol %;

09 have a maximum oxygencontent of 9.0 ppmv;

10 have a maximum nitrogencontent of 4.5 mol %;

11 have a total non-hydrocarboncontent of 5.5 mol %;

12 have a maximum mercury content of0.01 microgrammes per Cubic Metre;

13 have such delivery pressure at theDeliver Point as may be requested bythe CATS Parties from time to timeprovided that such pressure shall notexceed seventeen thousand twohundred and thirty (17,230) kPaGauge; and

14 have a maximum entry temperatureof 51 deg C.

9.2. Gas Redelivery Specification

01 commercially free from objectionableodours and from materials or othersolid or fluid matter which might causeinjury to or interference with the Transcotransportation and distribution network;

02 hydrocarbon dew point which at allpressures up to and including 7,200kPa Gauge does not exceed -2 deg C;

03 water dew point not greaterthan -10 deg C at 7,200 kPg(g);

04 maximum hydrogen sulphidecontent to be 3.3 ppmv;

05 maximum total sulphur contentto be 15 ppmv;

06 maximum carbon dioxide contentto be 2.9 mol %;

07 maximum total non-hydrocarboncontent to be 7.0 mol %;

08 maximum nitrogen contentto be 5.0 mol %;

09 maximum oxygen contentto be 10.0 ppmv;

10 Wobbe Index which is not morethan 51.2 Mega Joules per CubicMetre and not less than 48.2 MegaJoules per Cubic Metre;

11 Gross Calorific Value which is notmore than 42.3 Mega Joules per CubicMetre and not less than 36.9 MegaJoules per Cubic Metre;

12 delivery pressure up to 7,200 kPaGauge; and temperature not less than1 deg C and not more than 38 deg C.

13 Incomplete combustion factorless than 0.48

14 Soot index less than 0.6

Note: if the CATS Terminal NTS inputspecification agreed between the CATSParties and the Owners of the NTS differsfrom this specification or is subsequentlychanged, to the extent they become lessonerous this specification should bedeemed to be amended to the CATSTerminal NTS input specification.

3635

09. Appendix 1: Specification Data (cont.) 09. Appendix 1: Specification Data (cont.)

SPECIFICATION PROPANE BUTANE

Moisture Content pass

Free Water Content None

DEWPOINT Less than -40C at 1.013 bara Less than -30C at 1.013 bara

VAPOUR PRESSURE 1434 kPa Gauge (maximum) 483 kPa Gauge (maximum)@ 37.8 deg. C

COMPOSITION (LIQUID VOLUME) (LIQUID VOLUME)

Nitrogen 0.1% (maximum) 0.1% (maximum)

Carbon Dioxide 0.1% (maximum) 0.1% (maximum)

Ethane (C2 hydrocarbons) 2.0% (maximum) 0.1% (maximum)

Propane 95.0% (minimum) 0.5% (maximum)

Mixed Butanes 2.5% (maximum) 95.0% (minimum)

Pentanes 0.1% (maximum) 1.5% (maximum)

Total unsaturated

hydrocarbons (olefins) 1.0% (maximum) 1.0% (maximum)

RESIDUAL MATTER: 10 10

Maximum R Number

Maximum O Number Pass Pass

CORROSION, COPPER STRIP

Maximum No. 1 No. 1

H2S 1 ppm (vol.) (maximum) 1 ppm (vol.) (maximum)

TOTAL SULPHUR (Maximum) 50 ppm (wt) 50 ppm (wt)

MERCURY 10 ppb (wt) (maximum) 10 ppb (wt) (maximum)

DELIVERY PRESSURE a maximum of 19 barg a maximum of 10.5 barg

DELIVERY TEMPERATURE 33˚C (maximum) 33˚C (maximum)

9.3. Product Redelivery Specifications

9.3.1. Propane and Butane Specifications

The Propane and Butane exportspecifications are set out hereunder.

The CATS Parties retain the right at itsdiscretion to vary the specifications from

time to time provided that at all timesthe delivered Product will be ofmerchantable quality. In all cases thetest methods shall be based on themost recently published standards.

SPECIFICATION TEST METHOD VALUE

WATER

Free Water Content none

REID VAPOUR PRESSURE ASTM D-323 12.54 psia (maximum)@ 37.8 deg. C

DELIVERY PRESSURE a maximum of 4.0 bar g

DELIVERY TEMPERATURE 33 deg. C (maximum)

9.3.2. Condensate CharacteristicsThe CATS Parties retain the right at theirdiscretion to vary the specifications fromtime to time provided that at all times the

delivered Product will be of merchantablequality. In all cases the test methodsshall be based on the most recentlypublished standards.

3837

10. Appendix 2: New EntrantCheck-list

10. Appendix 2: New EntrantCheck-list (cont.)

This checklist is the final stage in the New Entrant process and follows after allthe necessary agreements are in place and signed.

Shipper CATS Action Action

Completed Completed

PROCESS/TIE-IN REQUIREMENTSEngineering Services Agreement signed X X

Received Shipper datagas composition, pressure, temperature, etc XReceived pipeline system presentation X

Received required process informationPressure envelope XGeneric specifications X

Contaminant details stipulatedMercury XMethanol XScavenger X

Received subsea layouts and tie-ins XCheck status of Pipeline Leak Detection System X

SHIPPER SYSTEM SAFETY/INTEGRITYShipper Statement of Readiness XShipper MAPD in place X

Integrity Management System in placeShipper XCATS (up-dated) X

Emergency Procedures in placeShipper XCATS X

TELEMETRY/DCS SYSTEMSTelemetry overview received XTelemetry requirements received XEquipment list issued for review XTelemetry end to end testing completed XBit error rate tests on data circuits completed XVoice communication checks completed XDCS signal checks completed (including offspec button) X

Control/ESD function tested XDCS configuration points identified XDCS/Allocation system modifications complete XFull function check signals just prior to production X

MEASUREMENT SYSTEMSInformation received (CMM) XTesting and Acceptance requirements received XComments submitted/non-conformances, exceptions XInterface meeting held XFDS, P&ID, GAs submitted for review XFAT procedures submitted X

Shipper CATS Action Action

Completed Completed

Invitation to acceptance testing issued (FAT)bench tests Xpanel simulation Xorifice test X

Commissioning procedures issued XOnshore commissioning checks completed XComprehensive equipment calibration procedures issued XInvitation to offshore commissioning X

Comprehensive completions dossier submitted(post start up-including calibration and test results, re-certifications). XLetter of acceptance received from CATS X

INSTALLATION/COMMISSIONING/OPERATIONSHAZOPs and Risk Assessments carried out andDocumented X

Tie-in and Commissioning proceduresAgreed XCompleted X

Commissioning chemicals and fluids identified/agreed XOperations chemicals identified XLatest sample analysis provided XStartup production forecast XOperations interface procedures in place XPossible offspec requests, conditions agreed X

EXPORT ARRANGEMENTSNTS capacity booked or equivalent XNGLS transport/storage contracts in place

C3 XC4 XC5+ X

NOMINATION/ ALLOCATIONHydrocarbon Accounting refresher TAA and PAA XHydrocarbon Accounting reporting interfacestatus check (admin procedures) XNomination/Allocation procedure training complete XTable top exercise for nomination/allocation complete XForecasting (commissioning and production)

Nominations XFlow Profiles X

DOCUMENTATION/PROCEDURESSignatory of Pipeline Hydrocarbon Accounting Procedures XSignatory of Transportation Allocation Procedures XSignatory of Plant Allocation Procedures XIssued Commissioning Procedures XIssued Start-up Procedures XAgreed Nomination and Reporting Procedures XReceived “Letter of Satisfaction” from CATS X

4039

11. Appendix 3: DCS DataTransfer Signals List

11. Appendix 3: DCS Data TransferSignals List (cont.)

There is a requirement for data transfer between the CATS Operator and third partyCATS entrants to enable CATS Operator to carry out pipeline control, stock allocationand leak detection. The majority of these requirements are defined in the CATSMeasurement Manual, however, there are some additional signals required foroperational reasons.

The following list identifies the full data I/O transfer requirements:

(Note that care should be taken with units of transfer, for example, if the actual hourlymass flow total for C1 as measured by the metering system is 163.2 tonne then thisshould be transferred as a value of 1632 tonnes*0.1 this approach is typical for all unitsshown in this way).

A. 3rd Party to Cats - Gas Metering

A1. Non Resettable Totals - sent every hour on the hourNote that these values are the true non resettable totals at the end of each hour, i.e.‘frozen’ on the hour such that they can be read by the CATS DCS prior to the next hourupdate. Totals should be transferred with sufficient precision to ensure accuracy to 0.1unit (e.g. 0.1 tonne), this shall require the use of more than a 16 bit number.

Update Frequency

Units Polling Time

Station Standard Volume Flow Total Sm3*100 1 hour

Station Mass Flow Total tonnes*0.1 1 hour

Station Energy Flow Total GJ*0.1 1 hour

A2. Hourly Cumulatives - reset to zero each hourNote that these values are the hourly report values and are therefore ‘frozen’ on the hoursuch that they can be read by the CATS DCS prior to the next hour update. Totals shouldbe transferred with sufficient precision to ensure accuracy to 0.1 unit, this may require theuse of more than a 16 bit number.

Hourly Mass Flow Total for N2 tonnes*0.1 1 hour

Hourly Mass Flow Total for CO2 tonnes*0.1 1 hour

Hourly Mass Flow Total for C1 tonnes*0.1 1 hour



Hourly Mass Flow Total for iC4 tonnes*0.1 1 hour

Hourly Mass Flow Total for nC4 tonnes*0.1 1 hour

Hourly Mass Flow Total for iC5 tonnes*0.1 1 hour

Hourly Mass Flow Total for nC5 tonnes*0.1 1 hour

Hourly Mass Flow Total for neoC5 tonnes*0.1 1 hour






Hourly Station Mass Flow Total tonnes*0.1 1 hour

A3. Daily Cumulatives - reset to zero at 06.00 am every dayNote that these values are the current daily cumulative totals from the hourly report valuesand are therefore ‘frozen’ on the hour such that they can be read by the CATS DCS priorto the next hour update. At 06.00 hours they are identical to the daily report values aslisted in section A4. Totals should be transferred with sufficient precision to ensureaccuracy to 0.1 unit, this may require the use of more than a 16 bit number.

Daily Mass Flow Total for N2 tonnes*0.1 1 hour

Daily Mass Flow Total for CO2 tonnes*0.1 1 hour

Daily Mass Flow Total for C1 tonnes*0.1 1 hour



Daily Mass Flow Total for iC4 tonnes*0.1 1 hour

Daily Mass Flow Total for nC4 tonnes*0.1 1 hour

Daily Mass Flow Total for iC5 tonnes*0.1 1 hour

Daily Mass Flow Total for nC5 tonnes*0.1 1 hour

Daily Mass Flow Total for neoC5 tonnes*0.1 1 hour






Station Daily Mass Flow Total tonnes*0.1 1 hour

Station Daily Standard Volume Flow Total Sm3* 100 1 hour

Station Daily Energy Flow Total GJ*0.1 1 hour

A4. Daily Data - sent every day at 06.00 am. Daily registers are then setto zero and today’s data becomes previous days dataNote that today’s values are the daily totals from the daily report values and aretherefore ‘frozen’ at 06.00 hours such that they can be read by the CATS DCSprior to the next daily update.

Yesterday’s values are from the previous daily report (i.e. 24 hours earlier).Totals should be transferred with sufficient precision to ensure accuracy to0.1 unit, this may require the use of more than a 16 bit number.

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Today’s Daily Mass Flow Total for N2 tonnes*0.1 daily

Today’s Daily Mass Flow Total for CO2 tonnes*0.1 daily

Today’s Daily Mass Flow Total for C1 tonnes*0.1 daily



Today’s Daily Mass Flow Total for iC4 tonnes*0.1 daily

Today’s Daily Mass Flow Total for nC4 tonnes*0.1 daily

Today’s Daily Mass Flow Total for iC5 tonnes*0.1 daily

Today’s Daily Mass Flow Total for nC5 tonnes*0.1 daily

Today’s Daily Mass Flow Total for neoC5 tonnes*0.1 daily






Today’s Station Daily Mass Flow Total tonnes*0.1 daily

Today’s Station Std.Volume Flow Total Sm3* 100 daily

Today’s Station Energy Flow Total GJ*0.1 daily

Today’s Station Average Std. Density kg/Sm3 daily

Today’s Station Average Gross Cal. Value MJ/kg daily

Today’s Station Average H2S Content ppmv daily

Yesterday’s Daily Mass Flow Total for N2 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for CO2 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for C1 tonnes*0.1 daily



Yesterday’s Daily Mass Flow Total for iC4 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for nC4 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for iC5 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for nC5 tonnes*0.1 daily

Yesterday’s Daily Mass Flow Total for neoC5 tonnes*0.1 daily



Yesterday’s Daily Mass FlowTotal for C8 tonnes*0.1 daily



Yesterday’s Station Daily Mass Flow Total tonnes*0.1 daily

Yesterday’s Station Std.Volume Flow Total Sm3* 100 daily

Yesterday’s Station Energy Flow Total GJ*0.1 daily

Yesterday’s Station Average Std. Density kg/Sm3 daily

Yesterday’s Station Average Gross Cal. Value MJ/kg daily

Yesterday’s Station Average H2S Content ppmv daily

Yesterday’s data only required for data recovery in the event of loss of daily data,Teesside DCS will retain data such that on request from allocation computer it canbe provided.

A5. Monthly Data - sent at 06.00 am on the first day of every monthNote that these values are the monthly totals from the monthly report values and aretherefore ‘frozen’ at 06.00 hours on the 1st day of each month such that they can beread by the CATS DCS prior to the next monthly update.

Totals should be transferred with sufficient precision to ensure accuracy to 0.1 unit,this may require the use of more than a 16 bit number.

Month’s Mass Flow Total for N2 tonnes*0.1 monthly

Month’s Mass Flow Total for CO2 tonnes*0.1 monthly

Month’s Mass Flow Total for C1 tonnes*0.1 monthly



Month’s Mass Flow Total for iC4 tonnes*0.1 monthly

Month’s Mass Flow Total for nC4 tonnes*0.1 monthly

Month’s Mass Flow Total for iC5 tonnes*0.1 monthly

Month’s Mass Flow Total for nC5 tonnes*0.1 monthly

Month’s Mass Flow Total for neoC5 tonnes*0.1 monthly



Month’s Mass FlowTotal for C8 tonnes*0.1 monthly



Month’s Station Mass Flow Total tonnes*0.1 monthly

Month’s Station Std.Volume Flow Total Sm3* 100 monthly

Month’s Station Energy Flow Total GJ0.1 monthly

Month’s Station Average Std. Density kg/Sm3 monthly

Month’s Station Average Gross Cal. Value MJ/kg monthly

Month’s Station Average H2S Content ppmv monthly

Note that H2S data is not included in the mass total throughput calculations but isreported as a parts per million content such that it can be reconciled, if necessary.

A6. Pipeline Monitor System Data

A6.1 Data from Metering SystemNote that these values are the current instantaneous values from theappropriate system and are therefore not ‘frozen’.

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11. Appendix 3: DCS DataTransfer Signals List (cont.)

Totals should be transferred with sufficient precision to ensure accuracy to 0.1 unit, thismay require the use of more than a 16 bit number.

Station Gross Calorific Value in use MJ/kg 30 secs

Station Moisture Dewpoint ºC 30 secs

Station Std. Volume Flowrate Sm3/h*1000 30 secs

Station Mass Flowrate tonnes/h 30 secs

Duty Chromat mol % N2 mol % 10 min

Duty Chromat mol % CO2 mol % 10 min

Duty Chromat mol % C1 mol % 10 min



Duty Chromat mol % iC4 mol % 10 min

Duty Chromat mol % nC4 mol % 10 min

Duty Chromat mol % iC5 mol % 10 min

Duty Chromat mol % nC5 mol % 10 min

Duty Chromat mol % neoC5 mol % 10 min






Station Energy Flowrate GJ/h 30 secs

Station Non Resettable Mass Total tonnes*0.1 30 secs

Chromat. Analysis Deviation Alarm 30 secs

Station Duty H2S Analysis ppmv 30 secs

Chromatograph data in use required on each cycle update - cycle time dependent uponequipment Moisture content may be measured in ppmv at constant pressure if required

A6.2 Data from DCS Process NodeNote that these values are the current instantaneous values from the appropriate systemand are therefore not ‘frozen’.

Gas Export Temperature ºC 30 secs

Gas Export Pressure KPa(g) 30 secs

Platform Blowdown Valve Open Status 30 secs

Platform Blowdown Valve Closed Status 30 secs

Gas Pipeline ESD Valve Open Status 30 secs

Gas Pipeline ESD Valve Closed Status 30 secs

Note: If pressure is regulated downstream of the metering point, then pressure andtemperature values downstream of the regulator are required.

A7. Operational Data - sent as initiated

3rd Party Platform Shutdown Signal (initiated by 3rd party)

B. 3RD PARTY TO CATS - LIQUID METERING (Applicable only to those fields withleak detection requirements via the CATS Riser platform)

B1. Data From Metering System/Process NodeNote that these values are the current instantaneous values from the appropriate systemand are therefore not ‘frozen’.

Totals should be transferred with sufficient precision to ensure accuracy to 0.1 unit, thismay require the use of more than a 16 bit number.

Standard Density (Station) kg/Sm3 10 secs

Mass Flowrate (Station) tonne/h 10 secs

Non Resettable Mass Flow Total (Station) tonne*0.1 10 secs

Liquid Export Temperature ºC 10 secs

Liquid Export Pressure KPa(g) 10 secs

Platform Liquid Blowdown Valve Open Status 10 secs

Platform Liquid Blowdown Valve Closed Status 10 secs

Liquid Pipeline ESD Valve Open Status 10 secs

Liquid Pipeline ESD Valve Closed Status 10 secs

Note: If pressure is regulated downstream of the metering point, then pressure andtemperature values downstream of the regulator are required.

C. CATS TO 3RD PARTY - sent as initiated

Onshore Terminal Shutdown Signal (initiated by CATS)

3rd Party Platform Shutdown Signal (initiated by CATS) - diverse communications route used

Communications Fault

cats technical brochure

Documents

allocation agreementpas

allocation systemp1nts

allocation agreementtas

allocation systemteg

allowable energy levelmaop

allowable energy levelzno

stock energy leveltaa

high pressurejt