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

Predictive modeling of CO2/CH4 adsorption is critical for optimizing the CO2-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 CO2 sequestration, where a significant portion of injected CO2 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 CO2 concentration on competitive adsorption and thus the potential for both gas recovery enhancement and CO2 storage. It demonstrates that Type III kerogen exhibits 60% higher CO2/CH4 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 CH4 recovery and CO2 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 CO2 adsorption. The findings provide theoretical guidance for synergizing secure and efficient CO2 sequestration with efficient shale gas extraction, leveraging the preferential adsorption of CO2 over CH4 in kerogen. This offers critical insights for energy development and carbon emission reduction under carbon neutrality goals.