Assessment of CO2 geological storage capacity based on adsorption isothermal experiments at various temperatures: A case study of No. 3 coal in the Qinshui Basin

Abstract

Carbon dioxide (CO 2 ) capture, utilization, and storage (CCUS) is an important pathway for China to achieve its “2060 carbon neutrality” strategy. Geological sequestration of CO 2 in deep coals is one of the methods of CCUS. Here, the No. 3 anthracite in the Qinshui Basin was studied using the superposition of each CO 2 geological storage category to construct models for theoretical CO 2 geological storage capacity (TCGSC) assessment, and CO 2 adsorption capacity variation with depth. CO 2 geological storage potential of No. 3 anthracite coal was assessed by integrating the adsorption capacity with the static storage and dissolution capacities. The results show that (1) CO 2 adsorption capacities of XJ and SH coals initially increased with depth, peaked at 47.7 cm 3 /g and 41.5 cm 3 /g around 1000 m, and later decreased with depth. (2) four assessment areas and their geological model parameters were established based on CO 2 phase variation and spatial distribution of coal thickness, (3) the abundance of CO 2 geological storage capacity (ACGSC), which averages 40 cm 3 /g, shows an analogous circularity-sharp distribution, with the high abundance area influenced by depth and coal rank, and (4) the TCGSC and the effective CO 2 geological storage capacity (ECGSC) are 9.72 Gt and 6.54 Gt; the gas subcritical area accounted for 76.41% of the total TCGSC. Although adsorption-related storage capacity accounted for more than 90% of total TCGSC, its proportion, however, decreased with depth. Future CO 2 -ECBM project should focus on high-rank coals in gas subcritical and gas-like supercritical areas. Such research will provide significant reference for assessment of CO 2 geological storage capacity in deep coals.