Mechanical responses of deep salt caverns under synchronous and asynchronous operation strategies

Abstract

In China, gas storage in deep salt caverns faces challenges due to high in situ stresses, elevated geothermal temperatures, and the presence of interbedded salt-mudstone formations. These factors lead to heterogeneous deformation and stress concentration, which adversely affect the stability and sealing capacity of salt caverns. To address these issues, this study systematically investigates the differences in the mechanical responses of a dual-cavern system located in a representative deep salt district under synchronous and asynchronous injection-production processes. The impacts of key operating parameters on the long-term deformation evolution of salt caverns under thermo-mechanical coupling are examined, and the effectiveness of the asynchronous operation strategy in optimizing the cavern stability is quantitatively evaluated. The results demonstrate that asynchronous operation significantly enhances the stability of the inter-cavern pillar. Specifically, this strategy disrupts the connection between zones with high stress-to-strength ratios, thereby reducing the risk of coupled failure between the two salt caverns. Furthermore, this strategy improves the distribution of the dilatancy safety factor of the surrounding rocks. Asynchronous operation also performs well in mitigating long-term deformation of the salt caverns, resulting in a lower risk of unilateral pillar instability, reduced cavern roof subsidence, and diminished volume shrinkage. Notably, asynchronous operation can effectively suppress cavern deformation under high-frequency injection-production cycles. Increasing the operating rate and decreasing the minimum pressure result in decelerating and accelerating deformation trends, respectively. Sensitivity analysis identifies the minimum pressure as the primary factor directly controlling cavern deformation, while operating frequency benefits most from the adoption of an asynchronous operation strategy. Overall, the findings of this study are expected to advance the construction and operational optimization of deep salt caverns for gas storage in China.