Assessing the Potential of Subsurface Offshore Resources for Geothermal Energy Production, Carbon Dioxide Storage, and Hydrogen Storage

Abstract This study evaluates the technical feasibility of offshore subsurface formations for CO2 storage, CO2 Plume Geothermal (CPG), hydrogen storage, and thermal energy storage. The goal is to understand how these processes behave in similar offshore reservoirs to understand the impact of water depth, geological and reservoir properties, and operational practices. The reservoir behavior was studied using numerical simulations and sensitivity analyses, focusing on thermoporoelastic stresses, pressure build-up, thermal drawdown, injection rates, and caprock integrity. The results show that shallow water depths delay fracture initiation, reduce stress-related risks, and lead to less heat loss in cases involving heat extraction. Large permeability emerged as the key factor in maintaining storage integrity, with low-permeability cases showing increased risks of fractures, especially during CO2 storage. Operational practices also played a critical role. For instance, reinjection after a shut-in or fully perforating a reservoir increased fracture risks, particularly in low-permeability formations. Strategies such as bottom-perforation injection and the use of multiple injection wells reduced fracture risks and helped maintain integrity. Thermal energy storage was shown to be viable offshore, but its success depends on selecting reservoirs with temperatures favorable to the injected water to minimize heat loss and maximize recovery. Hydrogen storage, although requiring larger injection pressures, proved feasible at the evaluated injection rates with no fractures, though higher rates could lead to fracture risks. Offshore reservoirs hold significant promise as multi-use platforms for CO2 storage, CPG hydrogen storage, and thermal energy storage. These findings show the importance of aligning operational practices with geological conditions to ensure storage integrity and optimize efficiency. Future research would focus on longer simulation durations, different geological settings, and economic considerations to deepen the understanding of these systems.