Analysis on the stability of salt-cavern underground gas storage during cyclic injection and production

The salt-cavern underground gas storage is characterized by large storage capacity, long running time and frequent injection-production operation, so it is crucial to analyze its stability during its cyclic injection-production operation. In this paper, the dilatancy damage, plastic zone distribution, horizontal displacement and volume shrinkage rate of salt rock were analyzed in the engineering background of one domestic salt-cavern underground gas storage. Based on its actual injection and production data, the process of injection and production was simulated by using the Flac3D finite difference software. And accordingly, the effects of salt rock properties, pillar stability and gas injection/production on the cavity stability were figured out. It is shown that after 7 years' cyclic injection-production operation, no dilatancy damage occurs around the salt cavity and the safety factor is higher than 5. Besides, the plastic zone of pillar between two cavities is not connected, the pillar is stable, and the maximum volume shrinkage rate of the cavity is 1.78%. It is indicated that the annual volume shrinkage rate of the cavity is in accordance with the safety standard and the underground gas storage is in the steady state.