Adsorption Modeling for CO2 Storage and Enhanced Gas Recovery in Kerogen-Variant Shale Reservoirs

Predictive modeling of CO 2 /CH 4 adsorption is critical for optimizing the CO 2 -enhanced shale gas recovery and geological carbon storage in shale formations. Shale reservoirs, characterized by their low permeability and high organic content, represent a promising target for secure CO 2 sequestration, where a significant portion of injected CO 2 can be permanently trapped via adsorption onto the organic matter surfaces. This study combines molecular simulations with theoretical modeling to develop a predictive adsorption framework for kerogen-variant systems, quantifying the impacts of kerogen type, temperature, pressure, and CO 2 concentration on competitive adsorption and thus the potential for both gas recovery enhancement and CO 2 storage. It demonstrates that Type III kerogen exhibits 60% higher CO 2 /CH 4 selectivity than Type I kerogen due to enhanced aromaticity, oxygen-functionalized surfaces, and hierarchical porosity. While selectivity declines by 30–55% with rising temperature, optimal displacement efficiencies (78–85%) and selectivity for both CH 4 recovery and CO 2 adsorption/storage occur at 3–10 MPa. To overcome traditional models’ limitations in capturing nonlinear couplings, we propose a dual-site thermodynamic-steric correction adsorption model (TS-CAM) incorporating kerogen-specific indices, dual-site assumptions, and temperature–pressure corrections. TS-CAM achieves >95% accuracy in predicting high-pressure CO 2 adsorption. The findings provide theoretical guidance for synergizing secure and efficient CO 2 sequestration with efficient shale gas extraction, leveraging the preferential adsorption of CO 2 over CH 4 in kerogen. This offers critical insights for energy development and carbon emission reduction under carbon neutrality goals.