Mini-Review on Influence of CO₂-Enhanced Coalbed Methane Recovery and CO₂ Geological Storage on Physical Properties of Coal Reservoir

Abstract

CO 2 -Enhanced Coalbed Methane Recovery (CO 2 -ECBM) not only enhances coalbed methane (CBM) recovery but also facilitates CO 2 geological storage within coal seams. The modification of coal reservoir physical properties due to CO 2 injection significantly impacts CBM recovery, CO 2 injection, and storage safety. This review initially focuses on elucidating the manifestations and underlying mechanisms of alterations in the physical properties of coal reservoirs, encompassing adsorption capacity, pore structure, permeability, and mechanical behavior. Subsequently, the influence factors of CO 2 -ECBM and geological storage on modification of coal reservoir physical properties are reviewed, such as temperature, pressure, reaction time, mineralogical characteristics, coal rank, and water. Finally, the challenges and perspectives are discussed, including (1) the role of coalbed water in modifying coal reservoir physical properties, (2) the implications of caprock alteration for the security of geological CO 2 sequestration, (3) the synergistic mechanisms underlying long-term storage of CO 2 within coal reservoirs, and (4) the heterogeneity of coal reservoir modification in three-dimensional space.