沙一下油藏CO2混相驱替提高采收率的研究

以沙一下区块油藏为对象,研究了CO2混相驱技术可行性及提高采收率,通过PVT实验和细管模拟实验,确定了油藏原油的最小混相压力为18.41 MPa,原油采收率达90.01%。实验结果表明,注气驱达到混相压力后,注入压力对驱油效率影响不大,而在混相压力以下的近混相区,注入压力对驱油效率影响非常大。通过长岩心驱替模拟实验,对比了水驱和CO2驱替效率,结果表明CO2混相驱提高采收率达40.8%。

Research on Increasing Recovery Efficiency in Shayixia Oil Reservoir by CO2 Miscible Displacement Agent

The feasibility of the application of CO2 miscible displacement technology and the mechanism of increasing the recovery efficiency in Shayixia Oil Reservoir were studied. The minimum miscibility pressure, i.e. 18.41 MPa, of the crude oil in the reservoir was identified in PVT experiment and slim tube simulation experiment, and the crude oil recovery efficiency was increased to 90. 01%. According to results of experiment and test, the injection pressure has little effect on oil flooding efficiency after the miscibility pressure is reached by injecting the gas flooding agent, and has significant effect on oil flooding efficiency in the near - miscible zone in which the pressure is lower than the miscibility pressure. The oil displacement efficiency of water flooding agent and that of CO2 miscible displacement agent were compared in long core displacement simulation test, and the results of test have shown that the recovery efficiency can be increased by 40.8% after CO2 miscible displacement agent-is used.