致密油藏注伴生气驱油可行性分析及效果评价

Feasibility analysis and performance evaluation of injecting associated gas for enhanced oil recovery in tight oil reservoirs

致密油藏在开发过程中注水困难,亟需探索补充地层能量的新方式,同时油藏伴生气难以规模性开发。为研究油藏注气可行性,在室内开展原油相态特征、注气驱混相机理及注气驱长岩心实验研究,分析了M区块原油的相态特征、注入气与原油的互溶特征、注气混相机理以及长岩心注气驱油动态关键指标变化规律,结合现场应用情况,对其应用效果进行分析。结果表明,地层压力16 MPa下,原油溶解伴生气体积膨胀了1.161倍,黏度降低了20.5%;地层温度65℃下,注伴生气驱替长岩心原油采收率比衰竭开采提高23.15%;油藏开发中后期注入伴生气可有效促进油水界面下移,射孔段剩余油增多,目的层段由高含水变为低含水。经X井现场应用,剩余油饱和度由注气前的28.62%升高至42.17%。注伴生气可有效提高油藏采收率,可为同类油藏制定开发方案提供重要实验数据支撑和理论指导。

The development of tight oil reservoirs faces significant challenges due to the difficulty of water injection,necessitating the exploration of new methods to supplement reservoir energy.Concurrently,the large-scale development of associated gas in these reservoirs is also challenging.To investigate the feasibility of gas injection in these oil reservoirs,laboratory studies were conducted on the phase behavior of crude oil,the mechanisms of miscible gas injection,and the long-core gas displacement behavior.The phase characteristics of crude oil from the M block,the miscibility properties between the injected gas and crude oil,the mechanisms of miscible gas flooding,and the dynamic changes in key indicators during long-core gas displacement were analyzed.Coupled with field application data,the effect of the method was evaluated.The research results show that at a reservoir pressure of 16 MPa,the volume of crude oil expanded by 1.161 times upon dissolving associated gas,with a viscosity reduction of 20.5%.At a reservoir temperature of 65℃,the oil recovery rate from long-core displacement using associated gas increased by 23.15%compared to depletion recovery.Injecting associated gas in the mid to late stages of reservoir development can effectively promote the downward movement of the oil-water contact,increase the remaining oil in the perforated interval,and transform the target interval from high water cut to low water cut.Field application in well X demonstrated an increase in remaining oil saturation from 28.62%before gas injection to 42.17%.Thus,injecting associated gas can significantly enhance oil recovery,which may provide critical experimental data and theoretical guidance for developing similar reservoirs.