  A promising option for storing large-scale quantities of green gases (e.g.,
hydrogen) is in subsurface rock salt caverns. The mechanical performance of
salt caverns utilized for long-term subsurface energy storage plays a
significant role in long-term stability and serviceability. However, rock salt
undergoes non-linear creep deformation due to long-term loading caused by
subsurface storage. Salt caverns have complex geometries and the geological
domain surrounding salt caverns has a vast amount of material heterogeneity. To
safely store gases in caverns, a thorough analysis of the geological domain
becomes crucial. To date, few studies have attempted to analyze the influence
of geometrical and material heterogeneity on the state of stress in salt
caverns subjected to long-term loading. In this work, we present a rigorous and
systematic modeling study to quantify the impact of heterogeneity on the
deformation of salt caverns and quantify the state of stress around the
caverns. A 2D finite element simulator was developed to consistently account
for the non-linear creep deformation and also to model tertiary creep. The
computational scheme was benchmarked with the already existing experimental
study. The impact of cyclic loading on the cavern was studied considering
maximum and minimum pressure that depends on lithostatic pressure. The
influence of geometric heterogeneity such as irregularly-shaped caverns and
material heterogeneity, which involves different elastic and creep properties
of the different materials in the geological domain, is rigorously studied and
quantified. Moreover, multi-cavern simulations are conducted to investigate the
influence of a cavern on the adjacent caverns.
