Hydrogen and Carbon Dioxide Kinetic Adsorption and Diffusion Behavior into Organic-Rich Shale: Implications of Mineralogy and Organic Content

Abstract

Geological storage of hydrogen (GSH) is a pivotal technology for advancing an industrial-scale hydrogen economy. Shale formations, known for their impermeable sealing and abundance, offer promising potential for secure GSH applications. However, the complex mineralogy and organic content of shale necessitate a detailed investigation. This study examines the potential of organic-rich shale samples from Jordanian oil source rocks for hydrogen (H₂) storage and carbon dioxide (CO₂) sequestration. Adsorption kinetics were measured at two different temperatures (303 and 333 K) and pressures (15 and 45 bar) using a volumetric experimental approach. Common mathematical models were applied to evaluate the adsorption data and calculate the diffusion coefficients. The results indicate that H₂ adsorption on shale surfaces occurs at significantly lower rates than CO₂, with H₂ being adsorbed approximately 2–7 times less as pressure increases from 0.1 to 68 bar. Both gases show increased adsorption with rising pressure and decreased adsorption at higher temperatures. The superior adsorption capacity of CO₂ highlights its potential as a cushion gas, facilitating the preferential in situ separation of H₂ during extraction processes. This study also uses two distinct shale samples to explore the impact of varying total organic carbon (TOC) and calcite contents on gas adsorption capacity. The diffusion coefficients for H₂ were found to be approximately 10 times higher than those for CO₂, offering critical insights into the dynamics of H₂ storage and retrieval in geological formations. The findings provide insights into H₂ storage and retrieval in geological formations and enhance the feasibility of utilizing shale formations as reliable seals or storage media for H₂.