Predictive Power of Theoretical Adsorption Models for Gases (H2, CO2 and CH4) in Overmature Kerogen: Arabian Journal for Science and Engineering

Underground gas storage (UGS) has been globally practiced for continuous energy supply, atmospheric CO2 reduction and green energy transition. Gases (carbon dioxide (CO2), methane (CH4) and hydrogen (H2)) can be stored in underground geologic media (e.g., depleted shale reservoirs and coal beds). The gas adsorption potential of shale under a wide range of pressure and temperature is necessary to estimate for development and storage purposes. While the adsorption potential of gases is governed by isothermal adsorption experiments, the mathematical models for adsorption provide a theoretical framework for the adsorption phenomena. In this study, we used molecular simulation results of the single-component adsorption behavior of CO2, CH4 and H2 on overmature kerogen to evaluate the predictive power of theoretical adsorption models. Specifically, we explain the suitability of Brunauer–Emmett–Teller (BET), Langmuir, Langmuir–Freundlich and Toth models for single-component CO2, CH4 and H2 systems. The results showed that the Tóth and the Langmuir models are better to choose for single species i.e. for CO2, CH4 and H2 adsorption behavior. In particular, BET and Langmuir–Freundlich isotherms showed the best fit for the adsorption behavior of H2 and the least to CO2. Langmuir isotherm is highly suitable to CO2/kerogen adsorption data and Toth isotherm fits best to CH4/kerogen adsorption data based on root mean square error (RMSE). These findings on the predictive power of theoretical adsorption models for gases (H2, CO2 and CH4)/overmature kerogen would be useful to screen and rank porous medium for underground gas storage. © 2023, King Fahd University of Petroleum & Minerals.