CO₂ storage potential of coal seam in Sanhejian closed coal mine

Geological sequestration of CO₂ in closed coal mines' coal seams is a significant method for CO₂ sequestration and an effective strategy to achieve short-term carbon emission reduction goals. This study focuses on the Sanhejian coal mine in Xuzhou City, Jiangsu Province. The study scrutinizes the features of the coal rock and the quality of the mined No. 7 and No. 9 coal seams. Additionally, it calculates the remaining coal resource reserves. The study also applies the fuzzy comprehensive evaluation method to identify nine main influencing factors for the CO₂ storage stability of the No. 7 and No. 9 coals. These factors include the stability factor, the nature of the overlying rock strata, the complexity of the geotectonic structure, the index of groundwater, the ratio of the sealed coal bed pressure to temperature, the ratio of the sealed coal bed depth to depth, the permeability of sealed coal beds, the degree of the hollowing-out collapse, and other relevant factors. We assessed the stability of CO₂ storage in No. 7 and No. 9 coals based on key influencing elements. We developed a CO₂ storage evaluation method to assess the CO₂ storage capacity of coal seams in sealed coal mines. The findings indicate that the remaining reserves of No. 7 coal and No. 9 coal in the Sanhejian closed coal mine are substantial. The comprehensive evaluation results for CO₂ storage stability are 86.209 and 87.698, respectively, indicating a higher level of stability and greater potential for storage. The CO₂ storage capacity of the No. 7 and No. 9 coal seams in the closed coal mines of Sanhejian was determined using the established evaluation method. We calculated the theoretical storage capacity to be 207.6 Mt and 80.9 Mt, respectively. This led to the division of the storage area into three levels: favorable, more favorable, and unfavorable. The work can establish a fundamental foundation for investigating the storage of CO₂ in coal seams within decommissioned coal mines.