非纯二氧化碳近混相驱可行性研究
The The Feasibility Study on Near Miscible Flooding by Impure CO2

CO2近混相驱对地层压力、原油物性和注入气纯度等要求不高，降低其操作成本，更具有应用可行性。本文基于低渗油藏E区块油藏和非纯CO2气性质，采用细管模拟及数值模拟等手段，研究近混相驱界限、CO2纯度下限要求以及应用可行性。研究结果表明，目标油藏最小近混相驱压力(MNMP)为(0.80~0.84) MMP、CO2纯度下限为57.6%；CO2纯度80%下采出程度比CO2纯度40%下提高了12.53%，仅比纯CO2混相驱采出程度降低了3.88%，进一步提高CO2纯度对采收率的提高幅度很有限，说明CO2近混相驱开发效果接近于混相驱。考虑到提纯CO2成本，推荐近混相注入气的合理纯度为80%。CO2近混相驱10年开发期采出程度高达58.28%，比水驱提高了17.67%，目标区块实施非纯CO2近混相驱开发可行性高。研究成果对我国低渗透油藏应用非纯CO2近混相驱开发技术具有重要指导意义。
CO2 near miscible flooding has low requirements on formation pressure, crude oil physical proper-ties and injected gas purity, so it is more feasible due to reduce its operation difficulty and cost. In this paper, based on the properties of low permeability reservoir E block and impure CO2 gas, the limit of near miscible flooding, the lower limit of CO2 purity and the application feasibility are stud-ied by means of slim tube simulation and numerical simulation. The results show that the minimum near miscible flooding pressure (MNMP) of the target reservoir is (0.80 - 0.84) MMP, and the lower limit of CO2 purity is 57.6%; the recovery degree under 80% CO2 purity is 12.53% higher than that under 40% CO2 purity, only 3.88% lower than that of pure CO2 miscible flooding. Further improving the purity of CO2 has limited effect on oil recovery, which indicates that the development effect of CO2 near miscible flooding is close to miscible flooding. Considering the cost of CO2 purification, a reasonable purity is 80%. During the 10-year development period of CO2 near miscible flooding, the recovery percent is as high as 58.28%, which is 17.67% higher than that of water flooding. The re-search results have important guiding significance for the application of impure CO2 near miscible flooding technology in low permeability reservoirs in China.