Hydrogen–Rock Interactions in Carbonate and Siliceous Reservoirs: A Petrophysical Perspective

Underground hydrogen storage (UHS) in carbonate and siliceous formations presents a promising solution for managing intermittent renewable energy. However, experimental data on hydrogen-rock interactions under representative subsurface conditions remains limited. This study systematically investigates mineralogical and petrophysical altera-tions in dolomite, calcite-rich limestone, and quartz-dominant siliceous cores subjected to high-pressure hydrogen (100 bar, 70°C, 100 days). Distinct from prior research focused on diffraction peak shifts, our analysis prioritizes quantitative changes in mineral concentra-tion (%) as a direct metric of reactivity and structural integrity, offering more robust in-sights into long-term storage viability. Hydrogen exposure induced significant dolomite dissolution, evidenced by reduced crys-talline content (from 12.20% to 10.53%) and accessory phase loss, indicative of partial de-carbonation and ankerite-like formation via cation exchange. Conversely, limestone ex-hibited more pronounced carbonate reduction (vaterite from 6.05% to 4.82% and calcite from 2.35% to 0%), signaling high reactivity, mineral instability, and potential pore clog-ging from secondary precipitation. In contrast, quartz-rich cores demonstrated exceptional chemical inertness, maintaining consistent mineral concentrations. Furthermore, BET and BJH analyses revealed enhanced porosity and permeability in do-lomite (pore volume increased >10x), while calcite showed declining properties and quartz negligible changes. SEM-EDS supported these trends, detailing Fe migration and textural evolution in dolomite, microfissuring in calcite, and structural preservation in quartz. This research establishes a unique experimental framework for understanding hydrogen–rock interactions under reservoir-relevant conditions. It provides crucial insights into mineralogical compatibility and structural resilience for UHS, identifying dolomite as a highly promising host and highlighting calcitic rocks limitations for long-term hydrogen containment.