Abstract: Uncontrolled blowout is a kind of extreme condition for gas storage cavern operation. Based on one-dimensional insulation flow theory, the analytical solution of pressure drop for salt cavern under blowout is obtained. The stress state, the deformation characteristics and the damage zone evolvement of the gas storage cavern are simulated and studied under three different operating modes, combining with the geological data of Jintan salt deposit. It is shown that the hard interlayers tend to failure before rock salt host; and the three failure regions around the interlayers expand to be sprinkled the whole salt cavern and extend 6-8 m along the radial direction during the unloading phase. The cavern convergence increases with the reduction of the initial internal pressure. There is a large volume loss of 5.02% for initial unloading pressure of 7 MPa. The strain rate of the surrounding salt enlarges to 10-2 s-1, which belongs to quasistatic bound, during unloading phase. The study indicates that the initial internal pressure is the key factor to maintain the storage cavern stability under the runaway blowout. Relatively high operating pressure is suggested to keep in the extreme disaster environment.

Key words: salt rock gas storage cavern, runaway pressure, stability, numerical simulation