Field Experimental and Theoretical Research on Creep Shrinkage Mechanism of Ultra-Deep Energy Storage Salt Cavern

Salt caverns are internationally recognized as excellent facilities for underground energy storage. Creep shrinkage deformation will occur in deep salt caverns under the action of high-ground stress, and it is a key factor to evaluate the safety of salt caverns. However, there has been no salt cavern creep shrinkage mechanism research on ultra-deep salt caverns. In this paper, the creep shrinkage mechanism of an ultra-deep salt cavern is established from the theory, numerical simulation, and field application. First, the actual creep field experiments (pressure testing and sonar testing) of the salt cavern (depth ≥ 2000 m) are carried out. Second, theoretical models of salt cavern creep shrinkage are established from four influence aspects (creep shrinkage, heat conduction, salt dissolution, and brine permeability). Third, a 3D geological model is built to analyze the creep stability of deep salt caverns based on their field conditions. The novelty of this paper is analyzing the creep shrinkage of the ultra-salt cavern by the theoretical model, numerical model, and field experimental data systematically. The results show that the shrinkage of the salt cavern and brine thermal expansion is key factors leading to pressure lifting of the salt cavern, which accounts for 0.6121 and 0.2147 in the four influence aspects. Three creep phases are obtained: rapid rising stage, steady rising stage and decelerating rising stage. The study provides a reference for the creep shrinkage and field application of salt caverns.