Study on the sensitivity of injection-production parameters for the long-term safety and stability of salt cavern gas storage

Abstract Injection-production operation parameters such as the minimum injection gas pressure (IGP:operation pressure), IGP interval, minimum IGP residence time and injection-production cycle period of long-term operation of underground salt rock gas storage will not only affect the storage capacity and working ability of gas storage but also be crucial to the safety and stability of the surrounding rock. A 3D geomechanical model of a salt cavern was established by WinUbro to study the stability of gas storage in the operation period. Five evaluation criteria for predicting the feasibility and stability of gas storage were comprehensively considered, including deformation, expansion safety factor, volume shrinkage, plastic zone and sensitivity. The stability of the surrounding rock of the cavern under different injection-production operation parameters and the degree of influence of each parameter on the stability of gas storage during the operation period are compared. The results show that the displacement of the surrounding rock and its deformation distribution range, the displacement of the roof of the cavern, the expansion coefficient of the surrounding rock of the salt cavern and the volume shrinkage rate of the salt cavern decrease significantly with the injection-production operation parameters. The plastic zone of the salt cavern increases with the rise in the IGP interval and the increase in the minimum IGP; however, the minimum IGP residence time and injection-production period have no obvious influence on the plastic zone of the salt cavern. The IGP interval and the minimum IGP have a positive influence on the plastic zone of the salt cavern, however, the minimum IGP residence time and injection-production period have no obvious influence on the plastic zone. The sensitivity coefficients of each injection-production operation parameter are ranked, from largest to smallest, as follows: IGP interval, minimum IGP, minimum IGP residence time and injection-production cycle. This conclusion can provide a theoretical basis for further optimizing the operation scheme design of salt rock gas reservoirs and ensuring the safety and stability of the long-term injection-production process of layered salt rock gas storage.