Studying injection-extraction induced thermal stress on hydrogen storage cavern in bedded salt rocks

In the peak-shaving process of underground salt cavern hydrogen storage, the surrounding rock experiences periodic stress and temperature variations over decades, leading to the induction of thermal stress that may compromise the safe operation of the storage during hydrogen injection and extraction. This study utilizes existing research on thermal stress associated with gas injection and extraction in salt caverns to establish boundary conditions for numerical simulations based on analytical solutions of gas temperature and pressure over time. It investigates the impact of injection-extraction cycles and rates on cavern stability, employing the tensile failure criterion as an evaluation metric. The findings reveal: 1. Tensile failure in the surrounding rock predominantly occurs during hydrogen extraction, with higher extraction rates and more frequent cycles exacerbating this failure. 2. During hydrogen extraction, tensile stress in the surrounding rock increases, causing failure near the interlayers of the cavern wall. Although tensile failure does not occur during hydrogen injection, stress concentration appears at the interface between rock salt and interlayers. 3. To mitigate tensile failure, it is recommended to increase the minimum internal pressure of hydrogen storage from 0.3 to 0.4 times the vertical stress at the cavern roof when designing for the maximum hydrogen extraction rate based on the minimum operating internal pressure of the cavern. By identifying critical factors influencing tensile failure, this study offers valuable insights for optimizing operational parameters of underground hydrogen storage, ensuring long-term stability and reliability in response to evolving energy storage demands.