塔河油田缝洞型碳酸盐岩油藏注气驱油提高采收率机理研究

Study on EOR mechanism by gas injection replacing oil in fractured-vuggy carbonate reservoir of Tahe Oilfield

为了研究塔河油田缝洞型碳酸盐岩油藏注气替油提高采收率机理,开展了原油物性实验、相态分析和注气驱油数值模拟研究。结果表明:塔河油田注氮气驱油为非混相过程,注二氧化碳驱油为混相过程;注氮气驱油的作用机理为降低原油黏度、体积膨胀补充地层能量、驱替微小孔径中的原油及重力分异形成人工气顶置换顶部剩余油;注二氧化碳驱油的作用机理为降低原油黏度、体积膨胀补充地层能量及降低油气界面张力;非混相注气驱油比混相开发效果好。

In order to study the EOR mechanism by gas injection displacing oil in fractured-vuggy carbonate reservoir of Tahe Oilfield,the physical property experiments,phase analysis and numerical simulation of gas injection displacing oil for Tahe crude oil are carried out. The results show that,N2 injection displacing oil in Tahe Oilfield is an immiscible process,and CO2 injection displacing oil is a miscible process. The EOR mechanism of N2 injection displacing oil is reducing oil viscosity,increasing formation energy by volume expansion of N2,N2 displacing the oil in small pores,and displacing the top remaining oil of reservoirs by artificial gas cap due to the gravitational differentiation. The EOR mechanism of CO2 injection displacing oil is reducing oil viscosity,increasing formation energy by volume expansion of CO2 and reducing interfacial tension between oil and gas. The development effect of immiscible displacement is better than that of miscible displacement.