Deformation characteristics of rock salt with mudstone interbeds surrounding gas and oil storage cavern

This paper discusses the deformation differences that occur due to the presence of thin mudstone layers in underground storage caverns in rock salt. Both plasticity and viscosity are considered in the displacement calculations. The results show that both creep deformation and deformation distinction (i.e. the differences in the creep behavior between the salt rock and the mudstone) are very large under the condition of high effective stresses. When the inner diameters of salt caverns are 40–60 m, the maximum radial convergence can reach 24 m and the deformation distinction can reach up to 6 m 30 years after the completion of cavern by solution mining. The affected areas are, however, are restricted to the vicinity of the cavern. The tightness of the cavern may not be violated if the distance between the caverns is greater than this amount. The extension of plastic and dilatancy zones in rock salt is limited to three times the cavern diameter. When elasto-plastic mudstone interbeds are included, tensile failure zones are present in the vicinity of the cavern and the plasticity zone stretches through the entire layer. This could cause a loss of cavern tightness or stability. If the mudstone interbeds creep (although the creep rate is 2 orders lower than that of rock salt) yielding is strongly de-escalated, but the deformation distinction is not affected.

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► The deformation differences of mudstone layers and rock salt in storage caverns are discussed.
► The deformation distinction is prominent under the condition of high effective stresses.
► The range of plastic and dilatancy zones is large for elasto-plastic media; but it is strongly de-escalated for creeping materials.
► The deformation distinction is not affected.