Suitability Evaluation of CO2 Geological Storage in Deep Coal Seam: A Case Study in the Eastern Margin of Ordos Basin, China

CO₂ coal seam storage is a significant component of carbon capture and storage technology, which serves as a pivotal technical instrument for the reduction of greenhouse gas emissions. The Ordos Basin develops a considerable number of unminable coal seams, which present an optimal place for CO₂ coal seam storage. This paper presents an investigation into the geological characteristics of the No.4 coal seam reservoir in the Shanxi Formation of Permian age and the No.8 coal seam reservoir in the Benxi Formation of Carboniferous age. To explore the adsorption capacity of coal rock and the sealing performance of caprock, relevant experiments were conducted. The results of the experiments demonstrate that the adsorption capacity of CO₂ on the coal samples is 1.11–3.73 times that of CH₄. The results of the breakthrough pressure test demonstrate that the mudstone sealing performance is the most effective, followed by dense limestone and sandy mudstone. Combined with the geological data of the study area, the analytic hierarchy process method was used to evaluate the CO₂ storage potential of coal seams. The areas suitable for geological storage of CO₂ in the study area are located in the central part and the south-central part.