页岩基质微观孔隙结构分析新方法

页岩基质孔隙主要包含有机孔隙和无机孔隙，页岩油气在有机孔隙和无机孔隙中的渗流机理不同，对页岩中有机孔隙和无机孔隙的微观结构进行定量表征具有重要意义.首先通过扫描电子显微镜(scanning electron microscope，简称SEM)实验分别获取具有代表性的页岩无机孔隙和有机孔隙扫描电镜图像，其中，无机孔隙相对较大，其图像的分辨率较低，有机孔隙相对较小，其图像的分辨率较高；然后，通过图像处理和马尔可夫链蒙特卡洛(Markov chain Monte Carlo，简称MCMC)法重构出相应的无机孔隙数字岩心和有机孔隙数字岩心，并提出局部叠加法构建同时包含无机孔隙和有机孔隙的页岩基质孔隙数字岩心；最后对无机孔隙数字岩心、有机孔隙数字岩心和基质孔隙数字岩心的结构特征进行了对比分析.结果表明，局部叠加法构建的页岩基质孔隙数字岩心能够同时描述页岩中的无机孔隙和有机孔隙结构特征，无机孔隙本身连通性较差，有机孔隙本身连通性较好，有机孔隙的局部孔隙度和局部渗透率较高，对页岩中的流体渗流有着重要作用.该方法为页岩中不同的孔隙结构特征描述和油气在纳米尺度孔隙中的传输模拟提供了一个可靠的研究平台. 

A New Method for Microscopic Pore Structure Analysis in Shale Matrix

It is important to quantitatively characterize the microscopic structures of organic and inorganic shale pores making up shale matrix, since shale gas and oil show different transport mechanisms in them. In this paper, the typical shale organic pore and inorganic pore images are obtained from scanning electron microscope (SEM) respectively, and it is found that the image with relatively larger inorganic pores has a lower resolution, while the image with relatively smaller organic pores has a higher resolution. Then, image processing and Markov chain Monte Carlo (MCMC) method are used to reconstruct the corresponding inorganic pore digital rock and organic pore digital rock, and local superposition method is introduced to construct the shale matrix pore digital rock including inorganic pores and organic pores. At last, the structure properties are compared and analyzed among the three inorganic pore, organic pore and matrix pore digital rocks. Results show that the constructed shale matrix pore digital rock with local superposition method could describe the inorganic pore and organic pore structures simultaneously. In addition the inorganic pores have a poor connection while the organic pores have a better connection, and a higher local porosity and local permeability, which is important to the fluid flow in shale rocks.A reliable research platform is established for different pore structure analysis and gas & oil transport simulation in nanoscopic pores of shale rocks in this study.