含裂缝岩石油水两相渗流的有限元模拟
Finite Element Simulation of Oil-water Two-phase Flow in Fractured Rocks
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摘要: 利用具备自主产权的国产有限元程序自动生成系统(FEPG), 模拟岩心尺度下裂缝-基质双重介质中油水两相渗流, 分析压缩系数、非均质性以及注水方式对两相渗流的影响, 并在此基础上考虑裂缝形态及分布方式, 得出裂缝对水驱油的影响规律。结果表明: 平行于主渗流方向的裂缝会导致见水时间缩短, 水相沿裂缝窜流, 降低驱油效果; 裂缝位于双重介质内部时, 基质中油相先向裂缝流动, 随后缓慢排出, 最终裂缝及其周围基质孔隙中的油大部分残余; 垂直于主渗流方向的裂缝能有效延长见水时间, 提高基质动用率。压缩系数小、非均质性弱的储层更适宜采用注水的开采方式; 脉冲注水能有效提高驱油效率, 加快油水界面推进速度, 且频率越高效果越显著。Abstract: Using Galerkin finite element method to simulate oil-water two-phase flow in fracture-matrix dual media at the core scale. The effects of compression coefficient, heterogeneity and water injection mode on the two-phase seepage are analyzed, and the influence law of fractures on water-flooding is derived by considering the morphology and distribution of fractures. The results show that fractures parallel to the main flow direction will reducing the oil displacement effect; When the fractures are located inside the dual medium, most of the oil remains in the pores of the fractures and its surrounding matrix; fractures perpendicular to the main seepage direction can improve the rate of matrix utilization. Reservoirs with low compression coefficient and weak heterogeneity are more suitable for water injection; pulse water injection can effectively improve oil displacement efficiency, and the higher the frequency, the more significant the effect is.