Underground Hydrogen Storage (UHS) in Natural Storage Sites: A Perspective of Subsurface Characterization and Monitoring

With the long-standing efforts of green transition in our society, underground hydrogen storage (UHS) has emerged as a viable solution to buffering seasonal fluctuations of renewable energy supplies and demands. Like operations in hydrocarbon production and geological CO2 storage, a successful UHS project requires a good understanding of subsurface formations, while having different operational objectives and practical challenges. Similar to the situations in hydrocarbon production and geological CO2 storage, in UHS problems, the information of subsurface formations at the field level cannot be obtained through direct measurements due to the resulting high costs. As such, there is a need for subsurface characterization and monitoring at the field scale, which uses a certain history matching algorithm to calibrate a numerical subsurface model based on available field data. Whereas subsurface characterization and monitoring have been widely used in hydrocarbon production activities for a better understanding of hydrocarbon reservoirs, to the best of our knowledge, at present it appears to be a relatively less touched area in UHS problems. This work aims to narrow this noticed gap, and investigates the use of an ensemble-based workflow for subsurface characterization and monitoring in a 3D UHS case study. Numerical results in this case study indicate that the ensemble-based workflow works reasonably well, while also identifying some particular challenges that would be relevant to real-world problems.