Research on high-pressure adsorption of supercritical CO₂ and the characterization of coal structure change in anthracite

CO 2 -Enhanced Coal Bed Methane ( CO 2 -ECBM) Technology has been widely used in deep coalbed methane (DCBM) extraction and CO 2 sequestration. CO 2 is in the supercritical state ( ScC - O 2 ) in deep coal seam reservoir, and has mechanical, physical and chemical effects on the coal body, making understanding ScCO 2 adsorption crucial. Based on the self-developed supercritical isothermal adsorption device, ScCO 2 high-pressure adsorption experiments were carried out in anthracite. Besides, using multiple characterisation methods to analyse the changes in microstructures of coal before and after ScCO 2 adsorption and reveal the mechanism of processing. The results indicate that an obvious mutation zone in adsorption during high-pressure conditions is carried out, with the minimal adsorption capacity in the mutation zone; 2) The effect of ScCO 2 on the microstructure of the coal mainly focuses on the micropores and mesopores (below 50 nm ), resulting in an improved coal adsorption capacity; 3)Providing three assessment indexes of potential of DCBM resource exploitation and CO 2 sequestration includes the buried depth, porosity and fracture permeability. The above research outcomes provide important theoretical foundation for the development of DCBM resources, assessment of CO 2 sequestration potential and engineering application.