Volume 50

Molecular simulation on H2 adsorption in shale kerogen nanopores and implications for underground hydrogen storage Fangtao Lyu, Zhengfu Ning, Ying Kang, Zejiang Jia

Abstract

Underground hydrogen storage (UHS) in shale reservoirs is increasingly recognized as a significant method for hydrogen storage, with H2 adsorption on reservoir rocks playing a crucial role in this process. In this work, we utilized molecular simulation techniques to investigate the adsorption behavior of H2 in the slit nanopores of shale organic kerogen and specifically analyzed the effects of gas pressure, pore size, reservoir temperature, and kerogen maturity on H2 adsorption performance. The results indicate that H2 forms a strong adsorption layer on the kerogen pore surfaces, and this layer density increases with rising pressure. The surface excess adsorption amount of H2 increases initially with pressure and then decreases slowly after reaching a critical pressure. H2 exhibits stronger adsorption performance in smaller pores, and higher temperatures are unfavorable for further H2 adsorption. Due to the chemical composition differences among various types of kerogen, the H2 adsorption capacity decreases with increasing maturity. However, the H2 recovery efficiency remains above 90% under the same conditions. In practical applications of H2 storage in shale reservoirs, it is advisable to prioritize strata with higher organic maturity. Additionally, it is essential to consider the impacts of reservoir pressure and temperature based on realistic conditions to select the most suitable reservoir depth for H2 storage. This study reveals the gas adsorption phenomena involved in UHS at the molecular level, providing insights into the optimal selection of H2 storage shale reservoirs.

Keywords hydrogen storage, shale, kerogen, adsorption, molecular simulation