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Online Field-Wide Gas-lift Optimisation. Dr Alasdair S Brown Technical Manager EPS Americas Inc. Presentation Structure. Introduction Single Well vs Field Wide Online vs Offline Case Studies Latin America Middle East Conclusions Questions. Single Well. - PowerPoint PPT Presentation
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Online Field-Wide Gas-lift Optimisation
Dr Alasdair S BrownTechnical ManagerEPS Americas Inc
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Presentation Structure
• Introduction• Single Well vs Field Wide• Online vs Offline• Case Studies
– Latin America– Middle East
• Conclusions• Questions
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Single Well
• Single Well Gas Lift Optimisation– Valve Spacing– Injection Depth– Valve Performance– GL Injection
Pressure
– Qgaslift
– CHP
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Single Well
• Conditions change– GL is inherently flexible– Design in flexibility
• Single well optimum– Well performance curve– Different for each well– Not necessary optimal
for system
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Gas Lift Optimisation
Gas Lift Compressor
Well
Well
Well
Well
Equal Gradients Method
Common Pressure
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Field Wide Optimisation
• Field Wide Gas Lift Optimisation– Distribution of Gas to competing wells– Pressure losses in gas lift distribution system– Pressure losses in production system– “Closing the Loop”
• Total system modellingTotal system modelling– including produced gas reinjection– Compressor performance
– Offline/Online
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Why Online?
• Large Number of Wells• Complex optimisation problem• Reduce cycle time
– Optimisation-to-implementation– Engineer’s time concentrated on value adding tasks
• Goals– Automate Process– Automate Repetitive Tasks– Optimise
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Sustainable Production Optimisation
Time
Incr
ease
d V
alu
e O
ver
‘Do
No
thin
g’
Simple Manual Optimisation
Complex Manual Optimisation (Offline GLO)
Complex Automated Optimisation (Online GLO)
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Automation & Optimisation• Off-line
– Data input manually into system model– Results from system model implemented manually
• Open loop– Data input automatically into model from SCADA– Results from model implemented manually
• Closed loop– Data input automatically into model from SCADA– Results from model implemented automatically via
set point controllers– Operator review may be required to ensure that
implemented results are “sensible”
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Off-line Optimisation
Optimiser
Field
OPERATOR • Advice• Approval• Implementation
Manual Data Input Data Output
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Open Loop Optimisation
Optimiser
FieldOPERATOR • Advice• Approval• Implementation
Automatic Data Input Data Output
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Closed Loop Optimisation
Optimiser
Field
OPERATOR •Advice•Approval•Implementation
Automatic Data Input
Data O
utp
ut
SetpointControllers
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Case 1: PdVSA On-Line
– SCADA data automatically loaded to give current block valve and compressor status and to constrain the optimisation to stay close to existing operating conditions
– Price/cost and equipment constraint data loaded from Corporate databases
– Gas injection well set-points sent directly to SCADA controllers (after production operator review as a block)
– Recommended pressure control valve set-points and compressor operating conditions sent to production operators in open-loop advisory messages
– Results stored in central database for access by other applications.
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PdVSA Systems Overview
PROCESS CONTROL
CENTRAL CONTROL
OPTIMISATION
CIS
RTU, PLC..
SCADA
ASMS, WTO, NN, OM&S, IS
CENTINELA, SIAL, SICOT..
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Integration Schematic
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DataReconciliation
DGO
Well ModelRecalibration
LegacyData
Systems
Pri
m.Changes
NeuralNets
Well
Test
System Geometry
ASMS
OM&S
Decoupled
CDMS
One iGES Server per BU
iGES-basedapplications
OracleIntermediate
DataBase
MiddlewareTransaction Services
SCADA ServerSCU 2
Real Time History
SCADA ServerSCU 7
Real Time History
PIHistorian
Crude/WaterTreatment
&Water Injection
Dynamic LeakDetectionPI Decoupled
from PRAP
Databaseservers
CDB
MasterRecollectors
PI API
SCADA ServerSCU 1
Real TimeHistoryAverageData
Real Time
SCADA ServerSCU 6
Real TimeHistoryAverageData
OPC
ABB Simcon
KBC UpRight EPS
Valmet
Stoner
ODBC
COM
System Architecture
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Process Control
Central Control
Optimisation
Corporate Systems
PdVSA Online GLO
GLO
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Process Control
Central Control
Optimisation
Corporate Systems
The Online GLO Application
RTU/PLC
Optimiser
Database
SCADA
Input Output
Input Output
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Online GLO Daily Operation
GLO
GLO is executed...
Gas lift rates andrecommendations downloadto SCADA
Gas Lift Well
MiniPlantas
Compressors
The results are evaluated...
Approval atSupervisory level
The SCADA Operatoraccepts the gas lift ratesand carries out adjustments
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La Salina Online
Tuned Well ModelsGenerate Operating PtWellhead PerformanceCurveWells in FlowgroupsFlowgroup Performance
SurfacesHP Gas Lift NetworkLP Gas GatheringNetworkComplete Network
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Field Implementation Results
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POIS• POIS = Production Operation Information System• Northern fields of Kuwait• Performed by consortium including EPS, Aspentech, Daelim• EPS role was to provide the optimization software, software integration
and detailed engineering models for five fields in North Kuwait. • The fields included 197 wells (411 well strings)
– 33 water injectors, – 91 gas lifted producers and – 30 produced with ESPs.
• The wells and fields are connected through a complex network allowing wells to be switched between high, medium and low pressure as well as ‘wet’ and ‘dry’ separator trains
• Total production 600 Mstb/day
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Design Brief
• Hydraulic model of GL Distribution System• Compressor Station behaviour and Performance
– Power turbines, compression, gearboxes, intercoolers, gas recycling
– Surge and stonewall constraints
• Multiphase Flow• Scalable to >1000 wells• Optimise non-hierarchical networks• Online Integration with
– Production Management System– DCS/SCADA System
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Objectives
• Data acquisition via SCADA to MIS (Aspentech)
• GL optimisation for new GL wells– GL being installed following water injection
• Automatic acquisition of WT data • Automatic well model recalibration• Automatic online GL optimisation calculation• Manual setting of optimised setpoints
(initially)
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PAS Concept
PAS
NewWellTest
WellFloWell Model
Compare with
trend
Engineerintervention
Rerun orretune
POIS
Fail
Pass
Manual Model Retune
Automatic Model Retune
Rerun Welltest
Data Transfer
Past data
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GLO Concept
GLO
ReO System Model
POIS
Network model
Wells Wells Wells Wells Wells
InitiateGLO run
GetUpdated
well models
Generatewell
performanceRun GLO
Convert tochoke
settings
New SettingsNew gas allocation
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Implementation
• Well modelling of all 411 wells (WellFlo)• Construction and tuning of network Model
(ReO)• Automatic tuning of Well models• Automatic GL optimisation• Integration with Aspentech MIS• Model maintenance and development
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Important Issues Identified
• Data Quality– Well data– production data– Surface network data
• Business processes– building use of POIS model into std. procedures– model maintenance– model enhancement
• Compressor optimisation• Multistage separation optimisation
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Network Config Modelling
Individual fields (viz., RA, SA, RQ, AD & BH) modelled as separate sub-sheets
Each GC has 7 headers that can take inflow from any or all wells
All fields interconnected through 3 Gathering Centres: GC-15, GC-23, and GC-25
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Network Config Modelling
Multiple GC & MF options for all the wells made network very flexible to accommodate any future flow path definition
Optimiser easily handled this huge network - over 40,000 objects!
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SCADA & POIS
Well Head PressureFrom 217 Wells
GC SCADA GC DCS
GC RTDB(POIS)
All DCS DATATRANSFERRED
RADIO LINK
PMDBALTAMEER
(POIS)
FINDER WELL INFORMATION
Business Process ExplorerGUI
WellFlo Reo&
WellFlo
Maintain Well Models(Administration of)
PAS
Hydrocarbon AccountingMaterial Balance
GLO
User
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Top Level Network
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Raudhatain-[RA]-GC15&GC25
Abdali-[AD]
Ratqa-[RQ]
Bahra-[BH]
Sabriyah-[SA]-GC23
C-GC15 C-GC25 C-GC23
Abdali:
16 Wells
to 2 GC
via 13 6in linesRatqa:
20 Wells
to 2 GC
via 36in & 10in lines
Raudhatain:
195 Wells
to 3 GC
thru’ 7 MF each
Sabriyah:
142 Wells
to 1 GC thru’ 7 MF
Bahra:
5 Wells
to 1 GC thru’ 7 MF
378 producers with choice of producing into any of 3 GCs through any of 21 MFs
Network Config Modelling
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RA Field Network
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Lift-Gas System
5x7 Possible inputs from RQ & AD fields
9 Sub-sheets holding 20-25 wells each
7x3 MF interconnecting all 194 wells across the field
7x3 MF outlets to production terminals
Lift gas to SA field
Network Config Modelling
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NP & GLwells (FG)
Multi-header choice for lift-gas
at present & for future
Multi-MF choice for production
at present and for future
Network Config Modelling
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GL Well Performance Surface Data
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Conclusions
• KOC currently producing to quota– Current capacity higher than quota
• (how much higher is unknown)
– However additional production can be allocated to NK– Cost reduction is additional benefit
• Reduction in admin overhead• Reduction in flaring• Potential reduction in new well requirement• Network reconfiguration
• Work practices need to change to extract full value from the system
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POIS project
• Client - Kuwait Oil Company• Year of Contract Award – 2000• Projected Value Generated:
– $100 million - $175 million per annum (projected)
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Questions?