Characteristics of pores and fractures in anthracite coal based on X-ray CT and FIB-SEM

Taking the anthracite coal in the southerm of Qinshui Basin as the research object, the pore-fracture network models of anthracite coal were established and the key parameters of pore-fracture network were extracted based on the X-ray CT （computed tomography） and focused ion beam scanning electron microscopy（FIB-SEM） imaging experiments. Then, the characteristics of pores and fractures in anthracite coal and their connection relationships were quantitative studied. The results show that the pores of anthracite coal in the southern Qinshui Basin are mainly mesopores with pore size less than 50 nm. Macropore content in anthracite coal is small, and microscopic fractures and cleats make a great contribution to pore volume in anthracite coal. The cross-section is predominantly irregular in shape, which means that the capillary resistance is large. The connectivity of the pores is well with multiple connected paths, which is beneficial to gas migration and output. With the decrease of the scale of pores and fractures, the connectivity and permeability of pore and fracture decrease. Mesopores, microscopic fractures, and cleats play an important role in the connectivity of anthracite coal. The connectivity and permeability of micrometer and millimeter scale pores and fractures in anthracite coal were improved by microscopic fractures and cleats, while the connectivity of nanoscale pores in anthracite coal was dominated by mesopores, which limited the connectivity of anthracite coal.