Supercritical CO 2 adsorption in a simulated deep coal reservoir environment, implications for geological storage of CO 2 in deep coals in the southern Qinshui Basin, China

摘要

CO 2 sequestration in deep, unmineable coal seams has been proposed as a method for offsetting increasing anthropogenic CO 2 emissions, while increasing natural gas production. Through laboratory experiments on gaseous/supercritical CO 2 adsorption using a manometric procedure, we investigated anomalies in supercritical CO 2 adsorption and determined CO 2 density‐temperature effects on adsorption capacity, which are closely related to the CO 2 storage potential in deep coal reservoirs. Results indicate that the revised Dubinin‐Radushkevich (D‐R) model can fit supercritical CO 2 adsorption data well, and there is a significant difference between excess and absolute adsorption capacity as CO 2 density increases. In the supercritical isochore, a rapid change in CO 2 density results in a transition from Langmuir‐like monolayer adsorption to multilayer adsorption, and there is an unsaturated multilayer system during this transition. Above the temperature at the cross point, the increasing of density decreases, and a negative dependence on temperature causes a gradual decrease in adsorption capacity. Coal reservoirs near the boundary between the supercritical isochore stage and fully supercritical CO 2 stage should be the prime target for geological storage of CO 2 . In order to better understand supercritical CO 2 adsorption behavior and identify target coal seams, further supercritical CO 2 adsorption experiments are needed in the southern Qinshui Basin.