Pore characteristics and influencing factors of coal reservoir in Tucheng Mining Area of Guizhou Province

The pore development characteristics of 7 main coal seams in Tucheng Mining Area were studied by mercury injection test and scanning electron microscope. Scanning electron microscope （SEM） observation shows that there are primary pores, pores, dissolution pores, mold holes, intergranular pores, micro cracks, etc. The primary pores and pores are distributed in belts and groups, and the connectivity of large pores between pores is poor; mercury injection test shows that the mercury injection pore volume of 3# coal seam is large and the proportion of medium pores is relatively large, and the pore volume of other coal seams is mainly small micropores, and the specific surface area of micropores is dominant; mercury injection curves of 3# coal seam are type I and type II, the mercury injection curves of 9#, 12#, 15# and 17# coal are type II, and the pores are mainly open pores with good connectivity; 291#, 292# coal mercury injection curves are type III, and the pores are mainly semi-closed pores with poor connectivity. The porosity, pore volume and specific surface area of coal reservoir are negatively correlated with the increase of vitrinite reflectivity, positively correlated with vitrinite components, negatively correlated with inorganic components, and weakly negatively correlated with water content and ash content. Through comparative analysis, it is considered that the 3# coal seam in the mining area has preferential pore conditions for CBM development.