Feasibility analysis of gas storage salt caverns in ultra-deep strata with thick interlayers

To address peak-shaving demand and ensure energy security, deep underground energy storage stands as a crucial approach in the development of future energy reserves. The target depth of the underground gas storage salt cavern (GSSC) in the Jingjie district of Yulin City, China, exceeds 2600 m. Based on the geological characteristics, a new scheme for constructing an ultra-deep GSSC with thick interlayers was proposed, and a geomechanical model was developed. The simulation results indicated that the thick interlayer in 9 sub-members collapsed when the cavern pressure decreased to 12 MPa. Based on an extensive evaluation system, the stability of the GSSC with thick interlayers was analyzed. The results indicated that as operational pressure increased, there was a decrease in the displacement, volume shrinkage (VS), and plastic zone, alongside an increase in vertical stress and the safety factor (SF). The minimum operation pressure (MOP) range of 28–48 MPa is proposed to adhere to the stability criteria. A novel method for gas storage utilizing the void space within bottom sediments is proposed. The available volume of the cavern using sediment voids (7.43 × 10⁵ m³) is about 1.36 times that of the conventional cavern (5.48 × 10⁵ m³). The use of sediment voids can significantly improve the energy storage capacity of caverns. The research results demonstrated that Jingjie ultra-deep GSSC has good feasibility.