碳酸盐岩双孔隙网络模型的构建方法和微观渗流模拟研究

The Construction method and microscopic flow simulation of carbonate dual pore network model

碳酸盐岩油藏作为全球的主力油气储集层,在微观尺度上分布有大量发育的大孔隙和微孔隙,研究不同孔隙对其微观渗流特征的影响具有重要意义.本文基于碳酸盐岩中分别描述大孔隙和微孔隙特征的单一尺度孔隙网络模型,利用整合法构建出能够同时描述大孔隙和微孔隙特征的双孔隙网络模型,最后模拟各网络模型的渗流过程,计算相应的渗流特征参数并同岩心实验室渗透率进行了对比.结果表明,基于整合法构建的双孔隙网络模型可根据区间域随机产生任意大小的网络尺寸,不仅同时包含大孔隙和微孔隙的几何拓扑结构信息,而且可同时描述大孔隙和微孔隙的渗流特征,能够较好描述真实碳酸盐岩油藏中多尺度孔隙特征.双孔隙网络模型的绝对渗透率和实验室岩心结果基本一致,水湿油藏条件下对比各网络模型的相对渗透率曲线发现,双孔隙网络模型的等渗点含水饱和度均大于大孔隙和微孔隙网络,其残余油饱和度明显减少,这是由于大孔隙和微孔隙的整合极大地提高了双孔隙网络的连通性,进而大幅度提高网络的渗流能力,本研究为碳酸盐岩微观渗流研究提供了重要的理论基础.

As the dominant hydrocarbon reserves in the world, carbonate media exists well-developed macro pores and micro pores at the microscopic scale, and it is important to study the influence of different pore characteristics on flow properties. In this paper, based on carbonate macro pore and micro pore network respectively, integration method is used to construct dual pore network which could describe the macro pore and micro pore characteristics simultaneously, the flow process is simulated and the flow properties of all pore networks are analyzed by comparing with the absolute permeability in laboratory test. Results show that, based on the size of stochastic domain, integration method could produce carbonate dual pore network with arbitrary sizes, the dual pore network could capture both the geometry-topology and flow properties of macro and micro pore system, which describes the multiscale pore characteristics in real carbonate reservoir. The absolute permeability of dual pore network matches that of laboratory core result which verifies the correctness of this method. Relative permeability curve comparison under water wet condition shows that, the isoperm water saturation in dual pore network is higher and the corresponding residual oil saturation is lower, the integration of macro pore and micro pore improves the connectivity and flow properties of carbonate rocks greatly, which provides an important theoretical basis to microscopic flow study in carbonate media.