Fostering Storage Integrity in Offshore Geological Hydrogen Storage Sites: Insights from Coupled Flow and Geomechanical Studies

Abstract The primary objective of this study is to address storage integrity concerns associated with underground hydrogen storage in offshore porous media. The focus is on preventing losses caused by the cyclical nature of hydrogen injection and withdrawal. The study aims to anticipate the emergence of storage integrity problems by determining the response of various parameters, which encompass pressure, temperature, displacement, strain, stress, and fluid composition. This study uses a synthetic reservoir model to explore diverse parameter responses across different phases of hydrogen storage and withdrawal. The investigation commences with a straightforward hydrodynamic numerical simulation model and progressively introduces complexities such as hysteresis, faults, thermal influences, and geomechanics. The values of pressure, temperature, displacement, strain, stress, and fluid composition are tracked at grid blocks that could be potential monitoring sites. The findings of this study show that pressures are the initial indicators of potential non-sealing faults or fractures. The arrival of fluid through these flow conduits occurs at a later time. This delay in fluid arrival can allow for timely measures to be taken to prevent fluid loss if continuous real-time monitoring is in place. Monitoring above the injection well is suitable for gauging strain, stress, and displacement, as these perturbations reach their maximum levels above the injection or production area. This study contributes novel insights into storage integrity during offshore hydrogen storage within porous media. By investigating various parameter responses throughout different stages of storage and withdrawal, the study introduces an understanding of pressure perturbations as early indicators of potential faults or fractures. Furthermore, the distinction between the timing of pressure perturbations and fluid arrival offers a valuable opportunity for preventative actions. The study also emphasizes the significance of monitoring location in relation to the leakage site for effective response detection. Finally, the practicality of monitoring above the injection well for specific perturbations is highlighted, enhancing the knowledge base for maintaining storage integrity.