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Houston, 4 th & 5 th February 2003

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.

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Houston, 4 th & 5 th February 2003

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  1. Spring 2003 Gas Lift WorkshopUnlocking the Value in Marginal Mature Fields:“Chasing the Barrels by Field-wide Gas Lift Gas Allocation Optimisation” Houston, 4th & 5th February 2003

  2. 10°W 0°E 10°E 60°N Aberdeen 50°N Scott / Telford UKCS Blocks 15/21a & b outer Moray Firth IVANHOE, ROB ROY, HAMISH FIELDS - LOCATION

  3. IVANHOE, ROB ROY, HAMISH FIELDS - DEVELOPMENT SCHEMATIC

  4. Hamish RobRoy Ivanhoe 0 2km IVANHOE, ROB ROY, HAMISH FIELDS - TOP RESERVOIR

  5. GR FDC/CNL K PHI DT Supra Piper Mid Shale Main Piper IVANHOE, ROB ROY, HAMISH FIELDS - RESERVOIR CHARACTER Basal shale

  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 • Projected end of field life 2006 • Current reserves estimates 187 mmbbl • Aquifer support + Water injection + Gas lift • The fields have always “over performed”

  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.

  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

  9. IVANHOE, ROBROY, HAMISH FIELDS - GAS LIFT SYSTEM • 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.

  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.

  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

  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

  13. IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING

  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.

  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.

  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

  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 + • +++++++++++++++++++

  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 + • +++++++++++++++++++

  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. 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 + • +++++++++++++++++++

  21. IVANHOE, ROBROY, HAMISH FIELDS - GAP MODELLING • 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

  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.

  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 andcontinuingmonitoringprocess( 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…)

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