LAUSR

Abstract Two-phase displacement of CO2- alkaline solution technology was proposed to address the obvious problems existing in the current coal mine gas control technologies, such as the gas enrichment and outburst risk caused by tradition CO2 injection technology, and the poor effect of conventional coal seam water injection technology. In order to investigate the damage characteristics of coal pore structure and permeability caused by two-phase displacement of CO2- alkaline solution, the composition and microstructure of coal after two-phase displacement of CO2- alkaline solution were tested experimentally, and the permeability experiment of two-phase displacement of CO2- alkaline solution was carried out. The results show that the reaction degree and dissolution of CO2-containing coal with alkaline solution are stronger than those with distilled water. The reaming effect of alkaline solution on CO2-containing coal is stronger than that of distilled water, and the two-phase displacement of CO2- alkaline solution has the greatest influence on mesopore and macropore; After two-phase displacement of CO2- alkaline solution, the permeability of coal sample increased by 47.6%–108.6%, and the water content of coal sample increased by 109%. The two-phase displacement of CO2- alkaline solution leads to the secondary development of coal pores, which significantly changes the coal pore structure, increases the permeability and water content of coal body, and thus obviously increases the gas extraction effect to reduce coal seam outburst risk and ensure coal mine safety production.