Investigating the Impact of Cyclical Hydrogen Injection and Extraction on Subsurface Reservoir Formation Rocks for Underground Hydrogen Storage

Underground hydrogen storage presents a promising avenue for storing excess renewable energy in the form of hydrogen gas, providing a reliable and scalable energy storage solution. However, the long-term feasibility and integrity of subsurface reservoirs utilized for hydrogen storage depend on understanding the complex interactions between hydrogen gas and the formation rocks. This research paper aims to comprehensively investigate the effects of cyclic injection and removal of hydrogen gas on the formation rocks of subsurface reservoirs intended for underground hydrogen storage. The study adopts a multi-faceted approach, integrating experimental analysis and geochemical investigations to capture the mechanical and geochemical responses of the reservoir rocks under cyclic loading conditions. Experimental studies involved laboratory-scale tests conducted to assess various rock mechanical properties using a sandstone core, such as strength, stiffness, and deformation behaviour, under the influence of 100 hydrogen injection and extraction cycles. Additionally, permeability alterations induced by hydrogen gas ingress and egress were examined to understand the impact on fluid flow dynamics within the reservoir rocks. Moreover, geochemical interactions between hydrogen gas and the formation rocks are investigated using XRD to see if any mineralogical changes and associated implications for reservoir integrity. From the experimental studies, it was observed that hydrogen storage was not found to adversely affect the strength of the rock. The outcomes of this research work hold significant implications for the design, operation, and management of underground hydrogen storage facilities. By enhancing our understanding of the mechanical and geochemical responses of subsurface reservoir rocks to cyclic hydrogen loading, this study contributes valuable insights towards optimizing storage operations, ensuring long-term reservoir integrity, and mitigating potential geological risks associated with underground hydrogen storage.