Behaviors of existing salt cavern group used for underground energy storage

Due to the situation that intensive cavern group system has to be used to improve resources (oil & gas) storage efficiency in China, the stability and contraction distortion of the existing salt rock storage group model are discussed. The single cavity model and cavern group model are built according to the result of sonar cavity survey, and the influence laws that how cavern group operating model effects the cavern stability are proposed through the comparison and analysis of the simulation results. The laws show that asymmetric volume shrinkage and irregular deformation can be induced by the following three factors, the difference in position and depth, formation dip of interbedded and shape difference between adjacent cavern; different from which the maximum displacement zone usually appeared in a fixed position near the waist in single cavern model; there are no fixed position of maximum displacement because of the influence of nearby caverns in the cavern group model; with the properties of high stiffness, low creep resistance and the strong shear strength near the salt-mudstone interface, the mudstone can improve storage cavern integrity and stability when it penetrates the whole cavern group; considering that the stratigraphic dip interlayer deformation property has bad influence on the cavern group leakproofness, the stretching at the mudstone-salt interface and the torsional bending of mudstone can cause cracking in the mudstone layer: and the breakthrough crack could make single cavern lose the ability to operate alone and then affect the whole operating efficiency of the cavern group.