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In low permeability sandstone reservoirs, oil production rate often decreases fast due to the difficulty of water injection. In order to solve this problem, a CO2 flooding trial was put into effect for block X which had been developed for ten years by water flooding. In this paper, the feasibility and necessity of CO2 flooding in block X was demonstrated from the view of both laboratory experiments and field experience. Experimental data shows that CO2 has good compatibility with the formation oil of block X due to its strong swelling function and viscosity reducing effect on oil. On the other hand, formation pressure of block X after water flooding was much lower than MMP, therefore, it was important to continuously supplement energy for CO2 flooding in block X. Multiple schemes for well pattern and soak time before oil production were designed and optimized by the method of numerical simulation. It is shown that linear well pattern can obtain higher oil recovery rate than inverted nine point pattern because formation oil in linear pattern can be displaced more uniformly. Besides, advanced CO2 injection while all oil wells being shut for more than three months can effectively boost reservoir pressure and production of block X. The project of CO2 flooding in block X after water flooding was proved to be quite successful in three aspects of enhancing oil recovery, economic benefits as well as CO2 storage. Statistic results showed a stable and high injection rate could be achieved for block X when the injected medium was changed to CO2 from water. Annual rate of oil production increased to 0.72% from 0.35% of water flooding and values of gas-oil ratio were controlled below 50 m3/t which was quite friendly to production equipment. In addition, up to 36.6 × 104 t CO2 had been stored in deep formation during the eight year after conversion, which would undoubtedly make a significant contribution to environmental protection. Finally, an economic evaluation for this CO2 flooding trial was conducted by cash flow method. It is shown that the break-even oil price of CO2 flooding enhancing oil recovery project in block X is about $75 a barrel and this figure would decrease if the price of CO2 can be controlled to cheaper level.

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Development Practice and Effects Assessment of CO2 Flooding in Low Permeability Reservoir After Water Flooding

  • 会议论文

  • 发表日期：

    2026年

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  • Xu-min Ding,
  • Shi-ning Li,
  • Shao-ming Yang,
  • Jia-wei Chen

摘要

In low permeability sandstone reservoirs, oil production rate often decreases fast due to the difficulty of water injection. In order to solve this problem, a CO2 flooding trial was put into effect for block X which had been developed for ten years by water flooding. In this paper, the feasibility and necessity of CO2 flooding in block X was demonstrated from the view of both laboratory experiments and field experience. Experimental data shows that CO2 has good compatibility with the formation oil of block X due to its strong swelling function and viscosity reducing effect on oil. On the other hand, formation pressure of block X after water flooding was much lower than MMP, therefore, it was important to continuously supplement energy for CO2 flooding in block X. Multiple schemes for well pattern and soak time before oil production were designed and optimized by the method of numerical simulation. It is shown that linear well pattern can obtain higher oil recovery rate than inverted nine point pattern because formation oil in linear pattern can be displaced more uniformly. Besides, advanced CO2 injection while all oil wells being shut for more than three months can effectively boost reservoir pressure and production of block X. The project of CO2 flooding in block X after water flooding was proved to be quite successful in three aspects of enhancing oil recovery, economic benefits as well as CO2 storage. Statistic results showed a stable and high injection rate could be achieved for block X when the injected medium was changed to CO2 from water. Annual rate of oil production increased to 0.72% from 0.35% of water flooding and values of gas-oil ratio were controlled below 50 m3/t which was quite friendly to production equipment. In addition, up to 36.6 × 104 t CO2 had been stored in deep formation during the eight year after conversion, which would undoubtedly make a significant contribution to environmental protection. Finally, an economic evaluation for this CO2 flooding trial was conducted by cash flow method. It is shown that the break-even oil price of CO2 flooding enhancing oil recovery project in block X is about $75 a barrel and this figure would decrease if the price of CO2 can be controlled to cheaper level.