Supercritical carbon dioxide storage diffusion effects and control methods in coal mining goafs

The storage of supercritical CO 2 (scCO 2 ) in abandoned coal mine goafs provides an effective approach for repurposing underground spaces while mitigating industrial CO 2 emissions. However, existing studies have primarily focused on caprock integrity, whereas scCO 2 migration through coal seams and its implications for long-term storage stability remain poorly understood. This study employs numerical simulations to investigate the migration behavior and spatial distribution of scCO 2 in coal seams. The results show that scCO 2 migrates substantially faster through coal seams than through caprocks, indicating that coal seams may serve as preferential migration pathways and pose potential risks to adjacent mining areas. For an inclined coal seam connected to the surface, the pressure at the coal outcrop reached 4.9 MPa after 10 years and 6.7 MPa after 100 years, indicating a pronounced risk of long-term leakage. Based on these findings, an active barrier strategy using a low-permeability chemically solidified artificial curtain is proposed to restrict scCO 2 migration. The results demonstrate that this barrier can effectively suppress CO 2 transport and reduce potential leakage risks. This study provides a practical approach for improving the long-term containment of CO 2 stored in abandoned mine goafs.