PHREEQC Reactive Transport Model Dataset for Shale Caprock–Cushion Gas Interactions during Underground Hydrogen Storage

This dataset contains the PHREEQC input and output files supporting the manuscript “Gas–Shale Interactions and Reactive Transport Assessment of Caprock Stability during Hydrogen Storage with Cushion Gases”. The simulations evaluate shale caprock geochemical behavior under fully water-saturated conditions for H₂–CO₂ and H₂–CH₄ gas systems. The dataset includes the model files used for short-term and long-term simulations, together with the kinetic-rate sensitivity cases. The simulations examine pH evolution, dissolved inorganic carbon, dissolved Si, Al, and K, and the response of the modeled mineral phases under the imposed geochemical conditions. These files are provided to support reproducibility of the reactive-transport modeling results reported in the manuscript.