Preliminary laboratory studies on hydrogen storage in a salt cavern of the Eocene Barbastro Formation, Southern Pyrenees, Spain

Abstract

[EN]Underground hydrogen storage (UHS) is emerging as a promising tool for managing surplus energy derived from renewable energy sources. Rock salt (halite) formations, particularly solution-mined salt caverns, offer a secure and efficient storage medium due to their low permeability, self-healing properties, and chemical stability. Laboratory experiments simulating reservoir-like conditions are essential for reducing uncertainties surrounding hydrogen–rock interactions prior to large-scale deployment. This study investigates the response of rock salt to hydrogen exposure under controlled conditions (10 MPa, 60 °C, 30 d) in an autoclave. Two samples from the Eocene Barbastro Formation (Southern Pyrenees), recovered from a deep borehole within a potential salt cavern-type storage site, were tested. The halite samples included impurities such as anhydrite, quartz, feldspars, dolomite, calcite, and phyllosilicates, allowing assessment of non-halite phase reactivity also. Results indicate no significant mineralogical changes after hydrogen exposure. Observed alterations were minor and limited to localised halite recrystallization, slight particle detachment, and occasional chloride precipitation. These findings suggest an overall mineralogical stability of the salt matrix and impurities under the tested conditions and scales. By improving our understanding of hydrogen–rock interactions in evaporitic settings, this study contributes to ongoing efforts to develop safe, science-based solutions for underground hydrogen storage in salt caverns.