Insights from Thermohydromechanical Simulations for Real-Time Monitoring of UHS in Saline Aquifers

Real-time continuous monitoring provides high-resolution spatial and temporal data for tracking fluid migration. In this study, we numerically investigate the temperature, pressure, strain and displacement responses in potential monitoring wells locations during cyclic hydrogen injection into saline aquifers. A coupled thermohydromechanical flow model was used to mimic the injection and withdrawal of hydrogen. Potential locations for injection and monitoring wells are mapped. The primary focus of the analysis was to determine the temperature, pressure, strain and displacement responses and what they could inform about hydrogen distribution. The study shows that pressure, temperature, displacement and seismicity are key parameters to track the cyclic behavior of hydrogen in the subsurface. The recommended locations for such measurements include for Pressure, Temperature, and Displacement, monitoring tools are best placed at the above-storage reservoir. For Strain, and induced seismicity – in or near the storage reservoir. These insights have practical implications for the design of monitoring wells equipped with monitoring sensors and for enhancing data interpretation practices. 1. INTRODUCTION Underground hydrogen storage in porous media has the potential to complement renewable energy resources by storing excess energy from these resources during low demand and releasing the energy during peak demand. Hydrogen can be produced via electrolysis. Excess energy can be stored as hydrogen in geological media like salt caverns or porous media. However, there are few experiences with hydrogen storage in porous media (summarized in Zivar et al., 2021), and the few cases are not hydrogen stored with 100% purity. There have been instances of the application of numerical modeling to understand the behavior of hydrogen in porous media (summarized in Okoroafor et al., 2023), but few of these works discuss or capture the geomechanical implications of hydrogen storage in porous media. The storage integrity of underground hydrogen storage in porous media remains a critical concern, especially regarding potential losses during the cyclical processes of hydrogen injection and withdrawal. Current understanding lacks insights into the geomechanical implications of hydrogen storage in porous media, making it imperative to address this gap. Thus, the primary objective of this study is to investigate and enhance storage integrity during hydrogen storage within porous media. Specifically, the study aims to anticipate and mitigate potential integrity issues by analyzing various parameters, including pressure, temperature, displacement, strain, stress, and fluid composition, throughout different hydrogen storage and withdrawal phases.