Poromechanical Evolution of Olivine-Rich Rocks During Serpentinization for Natural Hydrogen

ABSTRACT: Natural hydrogen is a promising sustainable energy source due to its environmentally friendly combustion, producing only water as its by-product. Serpentinization, which involves oxidation of ultramafic rocks with water to form serpentine while producing hydrogen is a key process for generating natural hydrogen. Although previous studies have explored the hydrogen generation mechanisms, experimental data on the poromechanical responses during serpentinization remain limited. In this study, we assess the effect of serpentinization on the poromechanical properties of olivine-rich dunite. Two dunite specimens - one saturated with water and the other dry - were subjected to a temperature of 220 °C and a pressure of 15 MPa for 14 days to induce serpentinization. After reaction, we conducted hydrostatic compression and triaxial experiments to assess poromechanical properties, while X-ray diffraction (XRD) analyses tracked the mineralogical changes. XRD results confirmed serpentinization through reduced olivine and increases in serpentine minerals. Poromechanical measurements indicated that serpentinization reduced the drained and unjacketed bulk moduli. This study provides experimental evidence of poromechanical and geochemical property evolution in olivine-rich rocks, offering insights into serpentinization and natural hydrogen. The findings can be used to optimize reaction conditions, enhance reservoir stability, and improve chemical reaction-coupled geomechanical modeling for efficient and sustainable hydrogen extraction.