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Evaluation of Different Water and Gas Injection Scenarios for Improving Recovery of One of the Iranian South West Reservoirs

Fallah Tafty, Mona | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39596 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Masihi, Mohsen
  7. Abstract:
  8. Increasing the global demand for energy and decreasing the production rate of oil reservoirs have forced the oil companies to focus on enhanced oil recovery (EOR) extensively. This paper summarizes the design, reservoir simulation, and results of different gas injection scenarios in one of the Iranian complex oil reservoirs. This complex reservoir is located in the south west of Iran and is made up of sandstone, limestone, and dolomite layers. It is an under saturated reservoir with no gas cap but with a strong aquifer. Oil production has started in 1977, but due to strong aquifer the production is still in the plateau period. In this study, by simulation, it is estimated that natural depletion will decline from plateau in 2014, so EOR methods must be started in 2013 to elongate the plateau period. Minimum Miscibility Pressure (MMP) was calculated for four different gases, CO2, N2, field separator gas, and natural gas of a nearby gas reservoir by simulation study of slim tube. The results showed that CO2 had the lowest MMP and could achieve miscibility condition in reservoir pressure in 2013. Reservoir Fluid was modeled using PVTi. A compositional model simulator (E300) was used and simulation was done up to 2040. Rate of injection was optimized for CO2 miscible injection. Miscible WAG process was investigated and sensitivity analysis was done on different parameters of WAG such as WAG ratio and WAG half-cycle and these parameters were optimized. Seven possible scenarios- natural depletion, water injection, miscible gas injection, optimized WAG, hybrid WAG, gas injection in the top and water injection in the bottom, and water injection in the top and gas injection in the bottom were compared. Results indicated that miscible gas injection yielded better recoveries than other scenarios with an increase of 17% in the recovery factor compared to natural depletion.
  9. Keywords:
  10. Water Alternative Gas (WAG)Injection ; Minimum Miscibility Pressure (MMP) ; Miscible Injection ; Enhanced Oil Recovery ; Slimtube Test

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