Study on pore structure characteristics of tectonic coal in Qinglong Coal Mine in Western Guizhou based on mercury injection

Tectonic coal is basically developed in coal and gas outburst areas. The pore structure of tectonic coal is an important factor influencing gas adsorption, diffusion and seepage. In order to study the development characteristics of different types of tectonic coal pores, taking the collected coal-rocks from the Qinglong Coal Mine as the research object, based on the mercury intrusion experiment to characterize the pore structure characteristics and combined with the fractal dimension to quantitatively characterize the pores, and analyze the complex characteristics of the pore structure of the Qinglong Coal Mine. The results shows: ①Tectonic coal types mainly include cataclastic structural coal, schistose structural coal, mortar structural coal, scaly structural coal and wrinkle structural coal, and with micropores and macropores developed in coals; the difference between brittle deformation and ductile deformation is significant. ②The micropores and macropores of cataclastic structural coal are dominated by semi-closed pores and open pores; the micropores and macropores of schistose structural coal have semi-closed pores and open pores; the micropores and transition pores of mortar structural coal are mainly semi-closed pores; the micropore morphology of scaly structural coal are mainly semi-closed pores, and the macropores pore morphology are mainly open pores and narrow-necked pores; the micropores and macropores in wrinkle structural coal are dominated by semi-closed pores and narrow bottle pores; ③When the mercury inlet pressure is in the low pressure section (0.01-0.69 MPa), in the stage of brittle deformation, the fractal dimension value changes; while in the brittle deformation stage, the fractal dimension changes law as mortar structural coal>schistose structural coal>cataclastic structural coal; while in the ductile deformation stage, the fractal dimension change law is wrinkle structural coal>scaly structural coal; when the mercury injection pressure is in the high pressure section (0.31-8.84 MPa), and the fractal dimension value of the crumpled coal in the ductile deformation stage is higher than that of the scaly coal. The fractal dimension of tectonic coal in the high-pressure section is generally higher than that in the low-pressure section, the degree of coal deformation under the high-pressure section is more complex, the seepage pores are more complex, and the pore structure has strong heterogeneity. The research results are of great significance for evaluating the recoverability of coalbed methane and revealing the risk of coal and gas outbursts.