Exploring the Potential of Organic-Rich Shales for In Situ Hydrogen Production through Thermal Stimulation and Fracturing.

The global pursuit of clean and sustainable energy has increased interest in hydrogen as a key energy carrier for achieving carbon neutrality. Consequently, global demand for hydrogen is anticipated to grow significantly in both the near and long term, necessitating the development of hydrogen production methods. While several researches have examined hydrogen generation through inorganic processes such as serpentinization, the potential of organic-rich sedimentary formations remains underexplored. This study investigates hydrogen-rich gas generating potential and fracture evolution of organic-rich rocks, with a particular focus on immature shales under controlled thermal treatment, aiming to enhance the yield of clean hydrogen gas. Pyrolysis experiments were conducted to simulate subsurface geological conditions, supported by comprehensive characterization using X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetric analysis (TGA). Gas Chromatography (GC) was used to analyze the gases generated at various heating temperatures and micro-CT imaging was used to examine the samples subjected to varying temperatures. The results show that hydrogen generation increases with temperature, with yields rising from 0.31% at 100°C to 36.02% at 450°C. High-resolution micro-CT imaging shows that thermally induced fractures developed predominantly parallel to bedding planes, enhancing permeability and facilitating gas migration. The progressive decomposition of organic matter, coupled with fracture development, significantly improved hydrogen release efficiency. These findings highlight the potential of organic-rich rocks, as viable and cost-effective targets for natural hydrogen exploration and in situ hydrogen gas generation and offering a pathway toward sustainable subsurface hydrogen exploitation strategies.