Consideration of the mechanical damage behavior of rock salt during calculation of infiltration-cracks in the edge zone of gas storage caverns

Abstract

Underground storage in salt caverns is a preferred method for the intermediate storage of natural gas to cover seasonal fluctuation in consumption and commercial gas storage. The prove of the stability and tightness of the storage required for safe operation is continuously adapted to the current state of the art. For many years, an intensive scientific investigation has been carried out within the frame-work of repository research with continuous optimization of the rock mechanical modelling of the material behavior of rock salt. From the elaboration of the research results on the pressure-driven infiltration processes into the primarily non-permeable salt rock, it emerges that during gas storage operation, in addition to the areal infiltration, the formation of macroscopic infiltration-cracks in the cavern surrounding salt rock is to be expected as well. This thesis deals with the computational simulation of macroscopic infiltration-cracks within the scope of theoretical modelling of salt cavern behavior during gas storage, taking into account additional mechanical damage processes in the rock salt. On the basis of variational calculus, the infiltration fracture propagation will be evaluated, considering different model approaches in material behavior of the cavern surrounding rock salt mass. As a result of the present work, it should be noted that with regard to the propagation of infiltration-cracks in gas caverns, constitutive model approaches for the description of the mechanical damage and healing behavior of rock salt can be neglected for a conservative assessment.