Gas adsorption behavior in organic-rich carbonate source rocks: Insights into hydrogen storage, methane recovery, and CO2 sequestration in oil shales

• Hydrogen adsorption is dominantly confined to organic matter, with negligible contribution from mineral surfaces. • Inorganic composition and pore structure isolation reveal key insights for improved CH 4 and CO 2 gas uptake. • This research provides critical guidance for optimizing hydrogen and methane storage in unconventional reservoirs, with CO 2 sequestration. Gas adsorption in unconventional petroleum source rocks, e.g. organic-rich mudrocks and shales, is influenced by significant heterogeneities in organic and inorganic composition, structure, and pore networks. An understanding of the interplay between these properties is essential for optimizing hydrocarbon extraction, CO 2 sequestration, and hydrogen storage in such reservoirs. Herein, the factors controlling hydrogen, methane, and CO 2 adsorption in unconventional organic-rich Jordan source rock samples are investigated, focusing on the roles of organic matter, mineral composition, and textural properties. The samples are characterized via multiple techniques, followed by adsorption experiments. The results reveal that H 2 has the lowest adsorption capacity, being influenced by kerogen structure and organic nanopores, while CH 4 adsorption increases with pressure and is primarily controlled by pore volume and surface area. The highest adsorption capacity is exhibited by CO 2 due to electrostatic and van der Waals interactions with both organic and mineral phases. After fast pyrolysis to remove organic matter, the H 2 adsorption is reduced and the CH 4 and CO 2 adsorptions enhanced. These results highlight the dependence of H 2 adsorption on the presence of organic matter, while CH 4 and CO 2 adsorption are strongly influenced by pore structure and development. Mineralogy plays a secondary but complex role, with quartz-rich samples exhibiting slightly higher adsorption than carbonate-rich samples. These findings reveal the interdependence between organic matter, mineral composition, and textural properties in governing gas adsorption in source rocks. This study offers critical insights for optimizing gas storage and improving energy recovery from unconventional reservoirs, along with effective strategies for CO 2 sequestration.