To enable large-scale underground hydrogen storage, porous rock formations can complement the storage space of salt caverns, which currently are investigated in first pilot tests in Germany. In porous rocks, mainly sandstone formations, several reactions and processes might impart on the storage of H2.
Here we present first data for five formations with an in depth petrographical and mineralogical characterization as well as experimental investigations with high partial pressures of H2 under near in situ pressure-temperature-conditions. The formations investigated include Tertiary sandstones (Bunte Niederrödern Schichten, Chatt), Tertiary limestone (Lithothamnienkalk), the Triassic Solling Sandstone and the Permian Wustrow and Schneverdingen Sandstone. For each formation, small diameter core plugs and thin sections were prepared from core samples for petrophysical and petrographic characterisation. One part of each core section has been crushed and milled, the pulverized rock material analysed for mineralogical and geochemical composition. In addition, the rock material was investigated in high-pressure experiments and the consumption of hydrogen quantified over a duration of 2 to 4 weeks. Overall, the hydrogen oxidation by H2-fluid-mineral surface reactions is limited; several mineralogical factors responsible for the oxidation are evident. Additional experiments investigating the kinetics of individual reactions, e.g. of iron oxides present in the rock material, complement the first assessment of geochemical reactions in these possible storage formations.