Maturity-controlled competitive adsorption of CO₂-H₂ and CH₄-H₂ gas mixtures in shale kerogen nanopores
Abstract
Organic-rich shales present significant potential for underground hydrogen storage, yet our understanding of the interactions of H2 with CH4 and CO2 in kerogen-hosted nanopores remain insufficient. This study constructs and validates macromolecular models of high-maturity and overmature kerogens via combining solid-state carbon-13 nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Grand canonical Monte Carlo and molecular dynamics simulations are performed, which reveal that kerogen maturity controls the competitive adsorption and diffusion of methane/hydrogen and carbon dioxide/hydrogen mixtures by regulating nanopore structure and surface chemical heterogeneity. Compared with high-maturity kerogen, overmature kerogen shows stronger confinement and a more pronounced near-surface enrichment of CH4 and especially CO2, which reduces the effective storage space available for H2. Mechanistically, CH4/H2 competition is driven by van der Waals interactions, whereas CO2/H2 competition is dominated by stronger electrostatic and inductive interactions, establishing a thermodynamic affinity order of CO2 > CH4 > H2. The radial distribution functions and interaction energies are measured, which confirm that CH4 and CO2 monopolize high-energy surface sites, relegating H2 to a weakly adsorbed, bulk-like state. Furthermore, molecular mobility follows the order of H2 > CH4 > CO2. Although H2 exhibits the weakest adsorption affinity, its high mobility suggests a stronger migration tendency and potential leakage risk, which should be considered when evaluating long-term containment security during UHS. Overall, this study reveals that maturity-controlled coupling exists between kerogen structure, competitive adsorption and gas transport, providing molecular-scale insights into hydrogen storage security, injectivity, leakage risk, and recovery in organic-rich shale reservoirs.
Document Type: Original article
Cited as: Liang, Z., Jiang, Z., Ostadhassan, M., Zhu, G., Li, Z., Arif, M. Maturity-controlled competitive adsorption of CO2-H2 and CH4-H2 gas mixtures in shale kerogen nanopores. Advances in Geo-Energy Research, 2026, 20(3): 259-276. https://doi.org/10.46690/ager.2026.06.07
DOI:
https://doi.org/10.46690/ager.2026.06.07Keywords:
Longmaxi shale, molecular structure reconstruction, underground hydrogen storage, competitive adsorption, kerogen, molecular simulationReferences
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Copyright (c) 2026 Zhikai Liang, Zhenxue Jiang, Mehdi Ostadhassan, Guangyou Zhu, Zhuo Li, Muhammad Arif
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