Comparative Analysis of Pore Structure and Adsorption Characteristics of Coal and Shale

In this paper, the pore structures of coal and shale were analyzed by the methods of high pressure mercury injection, low pressure N2 and CO2 adsorption. On this basis, the adsorption characteristics of CO2 and CH4 on coal and shale at different temperatures were studied using weight adsorption instrument. The results show that the micropore is more developed in coal seam, and the specific surface area and pore volume of micropore of coal are higher than those of shale. The mesopore of shale reservoir is more developed, and the specific surface area and pore volume of mesopore of shale are higher than those of coal seam. There are more macropores in coal seam, and the connectivity of macropore in shale is better than that in coal seam. The adsorption capacities of CO2 and CH4 in coal seam is one order of magnitude higher than those in shale, and the influence of micropore on the adsorption of CO2 and CH4 is more obvious. CO2 and CH4 have stronger adsorption affinities on the surface of coal matrix. The adsorption capacities of CO2 and CH4 are in positive proportion to the absolute value of the surface potential. When CO2 and CH4 are adsorbed in the coal reservoir, the surface potentials are higher. Compared with shale reservoir, deep coal reservoir has larger gas content and is more conducive to the sequestration of a larger amount of CO2.