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.
Taking the rock of the tight sand gas reservoir of Xujiahe Formation in western Sichuan region as the study objects,the 3D digital core models with real pore throat structure were reconstructed by combining the micro-CT scanning with the Avizo,which were used to investigate the characteristics of pore structure. Combing the digital core with finite simulation Comsol,the visualization of water driving gas process based on digital rock could be realized. Based on this method, the water driving gas simulation is done for investigating the influences of micro-pore structure on gas-water two phase flow. The results indicate that the distributions of pore throat of the tight sand are mainly contiguous and isolated. The contiguous pores may be related to the residual intergranular pores or intergranular dissolved pores,whereas the isolated pores may be related to the intragranular dissolved pores. The equivalent pore sizes are less than 0. 5 μm. The pore structure of the samples with the poor reservoir properties is morecomplicated than that of the samples with the good reservoir properties,and the proportion of the smaller pore of the former is higher,which is less contribution to the permeability. During the displacing gas by water,the micro-pore structure would change the shape of the flooding frontier and generate the tonguing phenomenon in the gas-water two phase flow.With the increase of the porosity and permeability,the displacement efficiency of the water would increase and the residual gas saturation would decrease.
出处
《地球物理学进展》
CSCD
北大核心
2017年第3期1019-1028,共10页
Progress in Geophysics
基金
国家自然科学基金联合基金重点项目(U1262209)资助
关键词
致密砂岩
微CT
孔隙结构
数字岩心
气水两相流
tight sand
micro-CT scanning
pore structure
digital core
gas-water two phase flow
