基于微CT技术的致密砂岩孔隙结构特征及其对流体流动的影响

发布时间：2018-07-24 14:58

【摘要】：以川西地区的须家河组致密储层岩石为研究对象,利用微CT技术结合Avizo软件先进的数学算法构建了三维数字岩心模型,可以表征砂砾岩储层岩石的孔隙结构特征,并将数字岩心和有限元软件Comsol结合,实现了基于数字岩心的水驱气模拟过程的可视化.并在此基础上开展了水驱气模拟,研究微观孔隙结构特征对岩心中气水两相流的影响.研究结果表明:致密砂岩岩心的孔喉分布状态主要呈连片状和孤立状,其中连片状孔隙在空间上连通性好,主要与残余粒间孔或粒间溶蚀孔有关,而孤立状孔隙在空间上多呈孤立分布,主要与粒内溶蚀孔有关;致密砂岩样品等效孔径主要分布范围在0.5μm以下,储层物性差的样品孔隙结构要比储层物性好的样品复杂,且前者的孤立孔隙多且小孔隙占比高,连通孔隙较少,其对渗透率贡献性少;在水驱气的过程中,岩心的微观孔隙结构将改变驱替前缘形状以及造成气水两相流中舌进现象;随着岩心孔隙度和渗透率增大,水驱气的驱替效率增大,残余气饱和度降低.
[Abstract]:Taking the dense reservoir rock of Xujiahe formation in western Sichuan as the research object, the 3D digital core model was constructed by using the microCT technology and the advanced mathematical algorithm of Avizo software, which can characterize the pore structure characteristics of the sandstone and gravel reservoir rock. The visualization of water drive gas simulation process based on digital core is realized by combining digital core with finite element software Comsol. On this basis, water drive gas simulation was carried out to study the influence of microcosmic pore structure on gas-water two-phase flow in rock core. The results show that the pore throat distribution of tight sandstone cores is mainly in the form of continuous flakes and isolated ones, in which the connected flake pores are well connected in space, which is mainly related to the residual intergranular pores or intergranular dissolution pores. The pore size distribution of the dense sandstone samples is below 0.5 渭 m, and the pore structure of the samples with poor reservoir properties is more complex than that of the samples with good reservoir physical properties, and the pore structure of the samples with poor reservoir physical properties is more complex than that of the samples with good reservoir physical properties, and the distribution range of the equivalent pore size of the dense sandstone samples is less than 0.5 渭 m. Moreover, the former has more isolated pores and higher proportion of small pores, less connected pores, and less contribution to permeability. In the process of water drive gas, the micro-pore structure of core will change the shape of displacement front and cause tongue entry in gas-water two-phase flow. With the increase of core porosity and permeability, the displacement efficiency of water drive gas increases and the saturation of residual gas decreases.
【作者单位】：西南石油大学油气藏地质及开发工程国家重点实验室;
【基金】：国家自然科学基金联合基金重点项目(U1262209)资助
【分类号】：TE31

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