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.