EXPERIMENTAL RESEARCH PROGRESS ON EFFECTIVENESS OF CO2-ECBM FOR ANTHRACITE OF QINSHUI BASIN, CHINA

Under support by the key project of National Natural Science Foundation of China (41330638), an experimental simulation system and its methodology of CO₂ Geological storage and CH₄ Enhanced Recovery (CO₂-ECBM) has been developed, experimental, numerical and physical analogue simulations and related test analyses have been further carried out with anthracite in Qinshui basin. Up to date, the following major cognitions have been achieved: mesopores (2-50 nm in aperture) play a major role in pore connectivity of anthracite reservoirs, particularly of which shrinkage-induced pores are first discovered and constitute the primary nano-scale interconnected pores; gas flow pattern was determined by pressure and size of pores and fractures, and slipstream and Knudsen diffusion effect in the micropores and mesopores increases rapidly with decrease of pressure; temperature and crustal stress are important factors affecting displacement efficiency of CO₂ injection into deep coal seam, and the efficiency becomes lower dependent of deeper depth since crustal stress affection is more dominant; ScCO₂ takes exogenous fractures and their successive fracs in coal as preferential path to migrate, and the exogenous fractures developing degree and connectivity determine injection effect of ScCO₂; geochemical reaction between ScCO₂ and coal under formation conditions plays a positive role in modifying coal reservoir structure due to dissolution of carbonate and clay minerals as well as organic matter in coal; volumetric strain induced by ScCO₂ adsorption is the primary cause of permeability and injectivity reduction of coal seam, and the volumetric strain of anthracite has a positive linear correlation with the absolute adsorption capacity of CO₂ and the reduction can be recoverable by injecting N₂ to displace ScCO₂ in coal; coal absolute adsorption capacity with ScCO₂ increases first gradually and then sharply dependent of dsorption equilibrium pressure, which implies that the absolute adsorption capacity and storage capacity of CO₂ can significantly increase with increasing of burial depth.The above results have preliminarily verified effectiveness of CO₂-ECBM with anthracite in Qinshui basin, and can provide positive theoretical evidences for engineering implementation of CO₂-ECBM with anthracite.