Hydrogen, carbon dioxide, and methane adsorption potential on Jordanian organic-rich source rocks: Implications for underground H₂ storage and retrieval

Hydrogen (H₂) storage in geological formations offers a potential large-scale solution suitable for an industrial-scale hydrogen economy. However, the presence of organic residuals can significantly influence the H₂ storage efficiency, as well as cushion gas performance, such as CO₂ and CH₄, injected to maintain healthy reservoir pressure. Thus, the H₂ storage efficiency and cushion gas selectivity were thoroughly investigated in this work based on H₂, CO₂, and CH₄ adsorption measurements using, for the first time, actual organic-rich carbonate-rich Jordanian source rock samples (TOC = 13 % to 18 %), measured at 60 °C temperature and a wide range of pressure (0.1 – 10.0 MPa). Initially, the samples were characterized using various analytical methods. Results demonstrated that H₂ adsorption capacities reached up to 0.47 mol/kg at 9.0 MPa. The measured adsorption of CO₂ was four times higher than H₂. An increase in TOC significantly decreased H₂ adsorption compared to CO₂ and CH₄. Additionally, CO₂ demonstrated preferential behavior as a cushion gas compared to CH₄, attributed mainly to the calcite content and presence of carboxyl and sulfonyl groups. This study provides fundamental data for understanding H₂ potential storage issues in an organic-rich rock formation and thus aids in the industrial implementation of an H₂ supply chain.