Stability analysis of CAES salt caverns using a creep-fatigue model in Yunying salt district, China

Rock salt is recognized as the optimal medium for the storage of hydrocarbons including petroleum, natural gas, compressed air, hydrogen as well as radioactive waste. A compressed air energy storage (CAES) station plays a critical role in the grid peak shaving with respect to solar and wind energy. This study analyzes the stability and safety of a CAES salt cavern in Yunying district, China. A 3D geomechanical model was established to analyze the cavern stability. The rheology of rock salt is described using a creep-fatigue model and the non-salt interlayer is characterized by a Norton power creep model. A novel evaluation system is proposed including displacement, dilatancy factor, equivalent plastic strain, and strength utilization rate. The results show that the operating pressures of 7–9 MPa satisfy the stability requirement of the CAES salt caverns during their 50-year operation. The simulation results are further compared with three cases: (1) when rock salt is described by the Norton power model, (2) when the operating periods are five days, ten days and one year, respectively, and (3) when the salt caverns are under different operating pressures. The values of each evaluation index using the creep-fatigue model are larger than those when using the Norton power model. The cavern deformation and volume shrinkage gradually reduce with increasing the cyclic period when using the creep-fatigue model, while an opposite trend was found when using the Norton power model. The deformation of the surrounding rock and the volume reduction both present an upward trend with a decrease of the operating pressures.