Basalt-Hydrogen-Water Interactions at Geo-Storage Conditions

Hydrogen geo-storage is a promising technology to achieve net-zero carbon emissions. Basaltic rocks have attracted limited attention, and only limited knowledge of the suitability of the basaltic formations for large-scale hydrogen storage is available. The complex in situ geochemical reaction of basalt-hydrogen is a key factor in evaluating the suitability of basalt for hydrogen storage. This paper investigates the geochemical interactions of hydrogen-basalt-water and evaluates the impact on basalt’s physical properties. Basalt samples collected from the CarbFix site in Iceland are treated with hydrogen-water for 108 days under 9.65 MPa at 348 K, and various analytical methods are employed. The results show minor dissolution of plagioclase minerals after hydrogen treatment due to the redox reactions of hydrogen. However, this dissolution behavior might contribute to the precipitation of calcium on the basalt surface. Images obtained from scanning electron microscopy reveal that only the filling of the cracks was removed after the treatment with no obvious crack growth, which resulted in a minor increase in the pores (4%). Contact angle measurements show that the surface wettability remains water-wet after the treatment. A blank nitrogen-DI water test is performed, to reveal the potential reactions between water and basalt, indicating that only minor changes exist. We conclude that the reactivity of basaltic minerals to hydrogen-water injection is low; thus, the suitability of basalt for hydrogen storage is promising. This work can be a suitable experimental framework to assist in evaluating the hydrogen reactivity to basaltic rocks and assessing the suitability for UHS.