ABSTRACT

As part of the former ‘Exploring for the Future’ program (2016–2024), the Australian Government committed significant resources to lay the foundations for the nation’s future hydrogen economy. One component was to understand how to identify, characterise, and operate potential hydrogen storage sites. This paper presents a case study of hydrogen storage in a depleted gas field, focusing on geomechanical behaviour, using data from the CO2CRC Otway International Test Centre in Australia. This study is the first to compare fluid dynamic behaviour and geomechanical risks of hydrogen storage with the more extensively studied methane and carbon dioxide (CO₂) storage. At reservoir depth, hydrogen exhibits large differences in density, compressibility, viscosity, and thermal properties compared to the other gases, necessitating different operational approaches for underground storage. The study’s uniqueness lies in the inclusion of coupled reservoir geomechanics with thermal simulation in reservoir and cap rock, using a high-resolution grid around the wellbore. A key finding is that hydrogen storage causes significantly less thermal perturbation compared to methane and CO₂ storage under an identical reservoir injection volume. The fault reactivation and wellbore fracturing risk due to thermally-induced stress changes are lower in hydrogen storage compared to CO₂ storage. Simulations suggest that reducing the injection rate dampens both temperature and pressure effects, further reducing the risk of wellbore fracturing and fault reactivation. This study highlights the potential advantages of integrating reservoir flow simulation with geomechanical risk assessment. Implementing dynamic control mechanisms in coupled simulations could optimise injection rates without compromising underground storage safety.