Prospective Evaluation of Gaseous and Mineralized Dual CO2 Sequestration in Mined-Out Area—A Case Study in Yu-Shen Coal Area

This research introduces a novel dual CO2 storage (DCS) approach by simultaneously storing CO2 gas in abandoned mines and securing it within mineralized backfill. For this method, CO2 mineralized backfill materials (CMBM) are pumped into CO2 mineralized storage segments (CMSSs) to support the roof while gaseous CO2 is injected into gaseous CO2 storage segments (GCSSs) to maximize storage amounts. This study focuses on the Yu-Shen coal area in Yulin City, Shaanxi Province, China. A three-level evaluation model was constructed to predict DCS feasibility based on the analytic hierarchy process (AHP) and fuzzy comprehensive assessment method. The model was generalized and applied to the whole coal area. Each indicator affecting adaptability is plotted on a thematic map to determine the corresponding membership degree. The aptness for 400 boreholes distributed in the entire area was derived and a zoning map which divides the whole area into different suitability was drawn. This paper puts forward a mathematical model for predicting DCS suitability. The findings establish an engineering paradigm that simultaneously addresses CO2 sequestration, industrial waste recycling, and ecological water table preservation. The research results can provide references for determining the site of DCS, contributing to the generalization of DCS in a larger range.