Experimental study on repair characteristics of damaged rock salt of underground gas storage

Damage in rock salt has significant implication on permeability, which affects the tightness of underground salt cavern gas storage in further. During the leaching of a salt cavern, the brine with formation temperature and pressure can promote the self-healing of rock salt in the excavation damage zone (EDZ). Laboratory tests were conducted to study the promoting effect. The permeability of two intact rock salt specimens was tested. Then they were damaged into two kinds of the state respectively through uniaxial compression. After that, they were put in saturated brine (with a temperature of 50 °C and pressure of 12 MPa, which we called the repair environment in this paper) for 7 d. Finally, the permeability and mechanical properties were obtained after the damaged specimens being repaired. The results show that the permeability of intact rock salt is below 10−19 m2; the permeability increases by more than two orders because of damage; the permeability decreases significantly after being repaired, which can be comparable to its intact state. Discussions of the repair mechanisms are presented (especially the mechanism of recrystallization), which may help to provide significant guidance for the study of the tightness and stability of gas storage facilities in China.