total system optimisation in gas-lifted fields
DESCRIPTION
Total System Optimisation in Gas-Lifted Fields. ASME/API/ISO Fall 2003 Gas-Lift Workshop , Kuala Lumpur, October 21-22, 2003 ZR Lemanczyk & CJN McKie Edinburgh Petroleum Services. Optimisation in Gas-Lifted Fields. - PowerPoint PPT PresentationTRANSCRIPT
1
e-petroleumservices.com
Total System Optimisationin Gas-Lifted Fields
ASME/API/ISO Fall 2003 Gas-Lift Workshop , Kuala Lumpur,
October 21-22, 2003
ZR Lemanczyk & CJN McKieEdinburgh Petroleum Services
2
e-petroleumservices.com
Optimisation in Gas-Lifted Fields
• Optimisation: maximisation of ‘benefit’ subject to constraints imposed by external conditions and the performance of the producing system– Reservoir– Wells– Pressure drops in pipes– Performance of surface equipment– Delivery pressures
3
e-petroleumservices.com
LiftGas-$
Oil
Water
+$
-$
Export Gas +$
Lift Gas
Single Well Optimisation
Gas Injection Rate
Oil
Pro
duct
ion o
r $
/day Increasing THP
PQ
4
e-petroleumservices.com
Single Well Optimisation
• Assumptions– Fixed tubing head pressure for all gas lift rates– Lift gas is available to the well at the rate and pressure
required
• Considered in the optimisation– Combined reservoir inflow and tubing outflow performance
• Not considered in the optimisation– Effect of other equipment on the well and vice-versa– How lift gas is supplied to the well– Whether lift gas injected into this well would
give more benefit in another well
5
e-petroleumservices.com
ProdManifold
ProdManifold
ProdManifold OilWater
+$-$
ExportGas+$
LiftGas
-$
LiftGas
LiftGas
LiftGas
-$ -$
Multi-well Optimisation
Flowlines
Flowlines
Flowline
Flowlines
6
e-petroleumservices.com
Multi-well Optimisation
• Assumptions– Fixed separator pressure– Fixed total lift gas availability
• Considered in the optimisation – Interactions between wells in production gathering
network– Optimal allocation of limited supply of gas between wells
• Not considered in the optimisation– How lift gas is supplied to the well– How changing operating conditions affect
total amount of lift gas available
7
e-petroleumservices.com
OilWater
Export Gas
Fuel Gas
Lift Gas
Lift GasManifold
ProdManifold
ProdManifold
ProdManifold
+$-$
+$
-$
ExternalFuel Supply
Total System Optimisation
P
P
PP
P
P
P P
Q
Q
Q
8
e-petroleumservices.com
Compressor Performance
Speed
Pow
er
100%
100%
DecreasingEfficiency
Gas Turbine
StonewallSurg
e
Suction Flowrate
Dis
charg
e P
ress
ure
IncreasingSpeed
Compression Stage
Fuel Gas
9
e-petroleumservices.com
ValveTubing
Relationship between CHP and Qgi
Ptu
b a
t opera
ting v
alv
e
Gas Injection Rate
CH
P
Gas Injection Rate
IncreasingCHP
10
e-petroleumservices.com
Well E Performance
11
e-petroleumservices.com
WPS for GL Optimisation
Well Completion Details• Tubing• Gas-lift Valves• Open interval(s)• Reservoir completion
Reservoir Pressureskh, Skin, PIProduction TestsFBHP, FBHT ObservationsFlowing Gradient Surveys
Production System Geometry/DimensionsWell Active/Inactive StatusesProduction Choke SizesCurrent Flow Routing (Block Valve Statuses)Surface Eqpt Active/Inactive StatusesCurrent Pressures and FlowratesEconomic Parameters
Well PerformanceSurfaces
OptimiserRecommendations
12
e-petroleumservices.com
Solution Technique
• A model is constructed containing all of the wells, the gathering & distribution networks and the surface equipment
• The optimal solution to the model is found using Sequential Linear Programming (SLP)– Generic optimisation capability which can be applied
to many different types of problems– Simultaneous simulation and optimisation– Proven ability to handle large, non hierarchical
networks with loops and branches andhundreds of wells
13
e-petroleumservices.com
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”
14
e-petroleumservices.com
Open Loop Optimisation
Optimiser
FieldOPERATOR • Advice• Approval• Implementation
Automatic Data Input Data Output
OPERATOR •Advice•Approval•Implementation
Data O
utp
ut
SetpointControllers
Closed Loop Optimisation
15
e-petroleumservices.com
performance
curves
Offline Optimization Workflow
Production Report
Enter and validate production test data, re-tune well models
Import updated well models into network models
Update network model
Corporateeconomic parameters
Current production equipment and network status
Run optimizationReview and output optimiser results
Implement in field
Update corporate information systems
Archive well and network models used for optimization
• Process takes weeks
• Highly skilled resource required
16
e-petroleumservices.com
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
17
e-petroleumservices.com
Sustainable Production Optimisation
Time
Incr
ease
d V
alu
e O
ver
‘Do
No
thin
g’
Simple Manual Optimisation
Complex Manual Optimisation (Offline)
Complex Automated Optimisation (i-DO)
Gains
Sustained Gains
Optimisation gains revert to norm as system changes: automation of process is key to sustain the gains
18
e-petroleumservices.com
Data
SCADAServer
Server
Web Client
Online Optimisation
Data
SCADAHistorian
ExpiredData
Conditions,Status
OptimizedSet-points
Results
Targets
LAN/WAN/Internet/Intranet
Review,Approval
EngineerPCs
Well PerfCurves
Network Model and Optimizer
Historical Data
Real-timeData
Production DataManagement
ProductionTests
WellModels
Data
CorporateDatabase
EconomicParameters
• Process takes minutes
• Fully automated
Process Data
19
e-petroleumservices.com
Conclusions
• Optimisation considering the total system can deliver additional production gains and costs savings over and above considering the production gathering network alone
• The capability to perform total system optimisation in gas-lifted fields exists today.
• A number of online gas lift optimisation systems have been installed and are operational today.
20
e-petroleumservices.com
3.5 million BOPD
Case Study: PDVSA - Venezuela
• Lake Maracaibo, Venezuela• Large-scale implementation of gas lift• Pilot Area (Centro Lago)
– Over 200 wells– 4 separation plants– 5 compressor trains
– 10 lift gas manifolds
1.5 million BOPD
MARACAIBOCABIMAS
21
e-petroleumservices.com
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.
22
e-petroleumservices.com
OilWater
Export Gas
Lift Gas
Optimal Separator Pressure
• Separator pressure has to be high enough to transfer gas to compression plant
• Total System Optimisation showed that it was possible to simultaneously reduce Psep and Qgi
• 3% increase in oil production, 14% decrease in lift gas requirement
SignificantPressureDrop
From Wells
To Wells
23
e-petroleumservices.com
Field Implementation Results
20000
11/06/00 11/07/00
Production History of Flow Station(Group of Gas Lifted Wells)
TotalOil
Rate
(bbl/day)
Start of NewGL Set Points
Average Rate 23.9 Mbbl/d
Average Rate 23.1 Mbbl/d
TIME
24 hr pumped volume of oil
LakeMaracaibo
24
e-petroleumservices.com
KOC POIS
In 2000 KOC awarded a contract for Production Optimization and Information Systems to a consortium including EPS
Objective - Deliver an integrated optimization and advisory system interfacing to the automation and SCADA systems covering four fields in North Kuwait
Scope– Four fields in North Kuwait including 411 well strings– Of these 33 are water injectors, 91 gas-lifted
producers, and 30 wells producing with ESP’s.– Complex network configuration allows wells to be
switched between high, medium and low pressure separators as well as between wet and dry trains.
25
e-petroleumservices.com
KOC POIS
• Production Operation Information System (POIS)• EPS in partnership with Aspentech• On-Line Optimisation (inc. GL) implemented 2000-
2002.• 253 NF + 91 GL + 34 ESP + 33 Injectors = ~400 wells• 5 Fields; 8 Producing Layers; 13 Fluid Models• 600,000 bopd• 217 SCADA – RTU Systems• Engineering support contract awarded 2003 despite
intense competitive pressure
26
e-petroleumservices.com
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 lines
Ratqa:
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 connected to 3 GCs through of 21 headers
KOC POIS
27
e-petroleumservices.com
Lift-Gas System5x7 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
Inside Raudhatain
KOC POIS
28
e-petroleumservices.com
NP & GLwells (FG)
Multi-header choice for lift-gas
at present & for future
Multi-MF choice for production
at present and for future
KOC POISInside Raudhatain Subsheet RA-1