Safety evaluation of salt cavern gas storage close to an old cavern

• Safety assessment is studied of salt cavern gas storage close to an old brine cavern.
• Geomechanical model is built of the new cavern close to an old cavern.
• Distance of the new cavern to the old cavern of Jintan salt mine is proposed.
• Different factors affecting the safety of the new and the old caverns are analyzed.

Uniaxial compression tests, triaxial compression tests, Brazilian disk splitting tests, direct shear tests and triaxial creep tests have been carried out on samples cored from Jintan mining district to determine their mechanical parameters. Based on the formation characteristic and the Sonar survey data of an old cavern, a 3D geomechanical model has been built of a cavern close to an old brine cavern. The effects of the distance between new and old caverns on the safety of the rock mass around the caverns are investigated. Deformation, plastic areas and volumes, effective strains, safety factors, and volume shrinkages are selected as the indexes to assess the safety of the caverns. The width of the pillar between the new and old caverns is optimized based on the calculated results. Experimental results show that the interlayer has large effects on the mechanical parameters of Jintan bedded rock salt, and should be considered in the numerical simulations. Numerical calculations indicate that the distance between the new and old caverns has large influences on the deformations, effective strains and safety factors, but has little effect on the plastic areas and volumes and volume shrinkages of the rock mass around the caverns. Although the dimensions of these old brine caverns are much smaller than those of the new ones, a distance between the new and old caverns of no less than two times the maximum diameter of the new cavern is proposed as the shape of the old cavern is poor.