Geomechanical Impacts of Underground Hydrogen Storage in Depleted Oil and Gas Reservoirs: A Case Study of the Madison Formation in North Dakota

The transition to renewable energy systems necessitates large-scale hydrogen storage solutions, with depleted oil and gas reservoirs emerging as promising candidates. This study investigates the geomechanical effects of underground hydrogen storage (UHS) on reservoir rocks and caprocks from the Madison Formation in North Dakota. Core samples were subjected to hydrogen exposure under realistic reservoir conditions (1600 psi, 200°C) over 30-day periods. Comprehensive analyses of mechanical and petrophysical properties revealed distinct responses between carbonate reservoir rocks and anhydrite caprocks. Carbonate samples exhibited increased porosity (0.74-5.79%) and permeability (4.32-8.70%), alongside decreased Young's modulus (2.10-3.67%) and increased Poisson's ratio (5.16-6.85%). Conversely, anhydrite caprocks showed more stable behavior with modest increases in Young's modulus (1.32-2.28%) and smaller changes in Poisson's ratio (2.69-3.66%). These findings indicate that while hydrogen exposure may weaken carbonate reservoir rocks, anhydrite caprocks maintain their sealing integrity. The study provides crucial insights for UHS implementation, highlighting the importance of rock-specific responses in storage system design and risk assessment. The results contribute to the development of safety protocols and optimization strategies for large-scale hydrogen storage in depleted reservoirs. These findings provide crucial insights into the geomechanical processes that occur during UHS and their potential impacts on the integrity of hydrogen storage in the depleted oil and gas reservoirs. This study underscores the importance of detailed geomechanical analysis for UHS and offers a comprehensive methodological framework for future investigations in similar geological settings.