Abstract: With the increasingly urgent demand of underground energy reserves, more and more underground salt rock gas storages are put into use. Underground salt rock gas storages are adopted around the world, because of their good features. Therefore, it is very significant to study the safety and stability of underground salt rock gas storage in operation period. During operation period, gas storage cavity is under time-varying pressure of the inner gas. At the same time, the storage has some risks because of objective uncertainties and it is difficult to study the storage risks with deterministic method. Jintan underground salt rock gas storage is taken as an example. The time-varying pressure curve is created and the transient mechanics method is used to study the long-term rheology of the underground salt rock gas storage. Based on stochastic mechanism method, the failure probability variation of the underground salt rock gas storage during operation period is obtained by ANSYS-PDS with taking the volumetric shrinkage as the control criterion. Calculations show that the displacement of the cavity increases in a wavelike form under the time-varying pressure of the inner gas and the amplification reduces gradually. The failure probability shows this variation: it grows slowly first and then grows fast gradually and it slows down and is stabilized finally. The influence of velocity of gas recovery and injection on the gas storage stability is discussed. Reducing the velocity of gas recovery and injection can suppress the volumetric shrinkage and improve the stability of gas storage. It is meaningful to the risk analysis and assessment of other similar underground salt rock gas storages.

Key words: salt rock gas storage, long-term rheology, numerical simulation, failure probability, velocity of gas recovery and injection