Abstract
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•H2, CH4, and CO2 adsorption isotherms measured for organic-rich source rocks.•TOC in rock influences gas adsorption behavior and storage capacities.•Organics, hydrophobicity, and pores are prominent influencers on adsorption capacity.•Gas adsorption in source rocks increases significantly with pressure.•Adsorption capacities of CO2 compared to CH4 indicate a better cushion gas for underground H2 withdrawal.
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.