houston, 4 th & 5 th february 2003
DESCRIPTION
Spring 2003 Gas Lift Workshop Unlocking the Value in Marginal Mature Fields: “Chasing the Barrels by Field-wide Gas Lift Gas Allocation Optimisation”. Houston, 4 th & 5 th February 2003. 10°W. 0°E. 10°E. 60°N. Aberdeen. 50°N. Scott / Telford. UKCS Blocks 15/21a & b outer Moray Firth. - PowerPoint PPT PresentationTRANSCRIPT
Spring 2003 Gas Lift WorkshopSpring 2003 Gas Lift Workshop
Unlocking the Value in Marginal Mature Fields:Unlocking the Value in Marginal Mature Fields:“Chasing the Barrels by Field-wide “Chasing the Barrels by Field-wide
Gas Lift Gas Allocation Optimisation”Gas Lift Gas Allocation Optimisation”
Houston, 4th & 5th February 2003
PCLPCL
20 April 2023 2
IVANHOE, ROB ROY, HAMISH FIELDS - LOCATION
10^0'W 0^0'E 10^0'E
60^0
'N50
^0'N
10°W 10°E0°E
60
°N5
0°N
Aberdeen
UKCS Blocks 15/21a & bouter Moray Firth
Scott / Telford
20 April 2023 3
IVANHOE, ROB ROY, HAMISH FIELDS - DEVELOPMENT SCHEMATIC
20 April 2023 4
IVANHOE, ROB ROY, HAMISH FIELDS - TOP RESERVOIR
0 2km
IvanhoeRob Roy
Hamish
20 April 2023 5
IVANHOE, ROB ROY, HAMISH FIELDS - RESERVOIR CHARACTER
Supra Piper
Mid Shale
Main Piper
GR FDC/CNL K PHI DT
Basal shale
20 April 2023 6
IVANHOE, ROB ROY, HAMISH FIELDS - PRODUCTION HISTORY
On stream 1989
Original reserves at start-up = 88 mmbls
Original field life 10 years
Projected field life extended several times
IV/RR/H PRODUCTION COMPARISON
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10
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30
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50
60
70
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
mb
op
d
original Actual
Projected end of field life 2006
Current reserves estimates 187 mmbbl
Aquifer support + Water injection + Gas lift
The fields have always “over performed”
20 April 2023 7
IVANHOE, ROB ROY, HAMISH FIELDS - GAS LIFT SYSTEM
Gas lift type & description: Continuous gas lift (gas is injected at a constant rate into the tubing) There is a common gas lift line into each subsea manifold, it is fitted with pressure & temperature transmitters located upstream the gas lift subsea choke.
Gas lift Characteristics: A system of subsea wellhead transmitters, each subsea wellhead is fitted with a flow transmitter, pressure & temperature transmitters, they can be interrogated in real time. There is also at a gas lift choke at each individual wellhead.
20 April 2023 8
IVANHOE, ROBROY, HAMISH FIELDS - GAS LIFT SYSTEM
Why should we care about gas lift optimisation?
Have a look at the production pie in IVRRH
IVRRH Production Pie
Natural flow Gas lift flow
20 April 2023 9
Gas lift contribution to overall production has increased from 40% at the beginning of last year to the current 55% .
This percentage was reduced to approximately 40% after the well intervention in IJ57 (re-perforations) and the new well drilled last year. It has increased again and will continue as the fields mature and water cut levels increase.
IVRRH Production: Natural flow vs Gas lift flow
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120
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1
Feb-0
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-01
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-01
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Aug-01
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2
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%
Natural flow Gas lift flow
IVANHOE, ROBROY, HAMISH FIELDS - GAS LIFT SYSTEM
20 April 2023 10
IVANHOE, ROBROY, HAMISH FIELDS - GAS LIFT SYSTEM
One key aspect of a gas lift system is the interaction between wells in the gathering network as back-pressure from additional gas in the flowline adversely affects production from all the other connected wells.
The ‘optimal’ gas lift injection rate generally determined from a single-well analysis method has limited validity in analysing a production network of gas lifted wells.
The oil production loss due to back-pressure effect in IVRRH gas lift system was estimated to be approximately 1,000 bbls/d.
Therefore the need for a system approach to gas lift allocation optimisation based on a model that would optimise field-wide gas lift allocation.
20 April 2023 11
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
GAP is a network analysis program that models the production gathering network from sandface through to the separator(s).
The production system is simplified by combining the responses at each node until the entire system is represented by a single optimised performance curve
20 April 2023 12
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
Define system components: tank or reservoir, wells, joints, pipelines, separators...
Draw the system schematic: graphically link components, e.g. pipeline connections
20 April 2023 13
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
20 April 2023 14
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
Generate & validate well performance: An automatic procedure allows GAP to control Prosper for generation of lift curve solutions.
Allocate lift gas: It is the calculation procedure used to assign gas to gas lifted wells and calculate production rates and pressures throughout the system.
Production optimisation: It consists of finding the optimum volume of lift gas to inject to each well. GAP allocates gas increments until all gas is allocated or maximum production is achieved.
20 April 2023 15
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
Gap uses three methods of optimisation:
Production: This option maximises the oil production rate, and GAP calculates the maximum rate that can be achieved for a specified volume of lift gas available.
Revenues: This option optimises the revenues generated by sales of oil & gas produced after taking into account the costs of processing water and injection gas.
Start-up scenario: This option optimises the amount of free gas produced, it will be used to rank wells in order of gas production in situations of limited lift gas supply.
20 April 2023 16
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
Once the system is defined (all wells with valid IPR & VLP data and all pipelines calibrated), the model solves the network system for pressure and rates at various nodes by either:
Network Solver option: It finds pressure and flow distributions in the network given fixed separator pressures. The gas allocation is set manually to each well and the model performs network calculations
Network Optimiser option: It optimises the returns of oil produced, revenues or gas produced. Let the model calculate the optimum amount of gas injected to each well to maximise production
20 April 2023 17
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
############################################
# RESULTS - SUMMARY REPORT FOR ALL WELLS #
############################################
System : IVRRH Production System Schematic
System type : Production
Optimisation Method : Production
Pipeline prediction : Pressure and temperature
Gas Available : 28.00 MMscf/day
Gas injected : 24.88 MMscf/day
Oil produced : 7924.46 STB/day
Gas produced : 3.47 MMscf/day
Water produced : 44432.25 STB/day
Liquid produced : 52356.72 STB/day
Name Oil
Produced
STB/day
--------------- -----------
57 3184.35
28 1367.95
31 703.44
24 666.84
40 78.20
27 1189.83
32 0.47
25 733.40
+++++++++++++++++++
+ End of report +
+++++++++++++++++++
20 April 2023 18
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
############################################
# RESULTS - SUMMARY REPORT FOR ALL WELLS #
############################################
System : IVRRH Production System Schematic
System type : Production
Optimisation Method : Production
Pipeline prediction : Pressure and temperature
Gas Available : 28.00 MMscf/day
Gas injected : 28.00 MMscf/day
Oil produced : 8481.35 STB/day
Gas produced : 3.57 MMscf/day
Water produced : 45987.56 STB/day
Liquid produced : 54468.90 STB/day
Name Oil
Produced
STB/day
--------------- -----------
57 3997.98
28 852.86
31 1014.03
24 565.47
40 47.33
27 1240.50
32 152.31
25 610.87
+++++++++++++++++++
+ End of report +
+++++++++++++++++++
20 April 2023 19
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
############################################
# RESULTS - SUMMARY REPORT FOR ALL WELLS #
############################################
System : IVRRH Production System Schematic
System type : Production
Optimisation Method : Production
Pipeline prediction : Pressure and temperature
Gas Available : 28.00 MMscf/day
Gas injected : 28.00 MMscf/day
Oil produced : 8836.45 STB/day
Gas produced : 3.67 MMscf/day
Water produced : 44688.90 STB/day
Liquid produced : 53525.36 STB/day
Name Oil
Produced
STB/day
--------------- -----------
57 4393.70
28 883.16
31 1092.68
24 575.84
27 1286.52
25 604.55
+++++++++++++++++++
+ End of report +
+++++++++++++++++++
20 April 2023 20
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
#####################################
# RESULTS - SYSTEM SUMMARY REPORT #
#####################################
System : IVRRH Production System Schematic
System type : Production
Optimisation Method : Production
Pipeline prediction : Pressure and temperature
Gas Gas Oil Gas Water Oil Gas Revenue
available injected Produced Produced Produced Gravity Gravity Generated
MMscf/day MMscf/day STB/day MMscf/day STB/day API sp. gravMM US doll
--------- --------- --------- --------- --------- --------- --------- ---------
0.00 0.00 5592.77 2.56 21791.55 33.7111 0.84
10.00 10.00 8391.19 3.48 36723.60 33.3662 0.82
15.00 11.66 8282.83 3.49 36670.50 33.3107 0.82
20.00 20.00 8706.09 3.56 42932.99 33.5149 0.81
25.00 25.00 8888.47 3.66 44481.04 33.5079 0.81
30.00 30.00 8769.06 3.65 44939.06 33.4983 0.81
35.00 30.42 8710.91 3.67 44505.83 33.4987 0.81
+++++++++++++++++++
+ End of report +
+++++++++++++++++++
20 April 2023 21
The incremental net oil production due to gas lift gas allocation optimisation is estimated at 6% of the total production, this is approximately equivalent to 400 bbls/d.
The modelling of gas lift gas allocation on a field-wide basis has allowed us to better understand and reduce the adverse back-pressure effects within the flowlines. This has accelerated cash flow and generated profit estimated at US $ 2.5 millions for year 2001.
306 days x 400 bbl/d x 0.85 (production uptime) = 104,000 bbls/year 104,000 x 24 $/bbl = US $ 2.5 millions
Unlocking Value: IVRRH Production
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Natural flow Gas lift flow Gas lift optimisation
IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING
20 April 2023 22
GAS LIFT PRODUCTION SYSTEM MODELLING - THE FUTURE
As This example shows, a field-wide gas lift allocation optimisation can contribute
to maximise the value of marginal and mature fields up to 10% gain in oil
production, accelerate cash flow and generate profit sooner.
20 April 2023 23
GAS LIFT PRODUCTION SYSTEM MODELLING - THE FUTURE
The key to gas lift optimisation modelling is predicting the effects of
changes, the gas lift optimisation should always be a proactive and
continuing monitoring process
( it is to do with being effective.
Effectiveness as doing the right thing, e.g. have a reliable simulation model…)
Once the monitoring process is predictable, the gas lift gas allocation
model becomes a production optimisation tool ( it
is to do with being efficient. Efficiency
as being better in what we do: optimise production…)