Research on the anisotropic characteristics of gas microscopic seepage in coal pores based on X-ray μCT scanning

The spatial structure of coal micro-pores is similar to the DNA of coal, it plays a decisive role in the occurrence state and seepage characteristics of coal bed methane. In order to reveal the anisotropic characteristics of gas seepage from a microscopic point of view, take the low-rank coal in the Ordos Basin as the research object, X-ray μCT scanning was carried out to reconstruct microscopic spatial structure model of coal pores.Numerical simulation of gas seepage in REV unit of coal micro-pores was carried out, the anisotropy characteristics of unidirectional and multidirectional gas micro-seepage were discussed. The results show that:in the micro-pores of low-rank coal, the pore pressure fluctuates only in a certain direction or within a certain seepage length; in the process of unidirectional gas seepage, the z direction permeability of Yangchangwan lignite is the highest, which is 0.64×10^-3 μm², inclined groove gas coal has the highest permeability in the y direction, which is 0.23×10^-3 μm²; in the process of multi-directional gas seepage, the +y, +x and -y directions in Yangchangwan lignite are the dominant seepage directions, and the flowrate accounts for 41.89%, 44.22%, and 38.43% respectively. The -y, +x directions in inclined groove gas coal are the dominant seepage directions, and the flow rate accounts for 51.67%, 66.66%, and 41.56% respectively.