Geomechanics Behavior of Salt Caverns following Depressurization and Backfilling

Abstract

Rock salt deposits are highly suitable for gas storage and for disposing of nuclear and highly contaminated waste. Large caverns can be easily created in rock salt deposits through dissolution. Rock salt exhibits extremely low permeability and self-healing properties, ensuring long-term tightness of the caverns. As a result, the demand for rock salt caverns is rapidly increasing due to the growing need for energy storage and environmental concerns regarding nuclear and highly contaminated waste. However, managing these caverns is challenging due to the viscoplastic nature of rock salt and its complex geomechanical behavior. The salt cavern may lose tightness for various reasons, compromising its storage functionality and potentially leading to instability due to the depressurization of the fluid inside the cavern. When necessary, stabilizing the salt cavern by backfilling it with solid material, such as sand, is a well-established and commonly adopted solution. Despite the extensive literature on rock salt mechanics and salt cavern behavior, there is a lack of research on the behavior of salt caverns following depressurization and backfilling. This paper investigates the evolution of stresses and deformations caused by depressurization followed by backfilling through numerical modeling. The presented numerical modeling results in this paper highlight the impact of the stress relaxation in rock salt following depressurization on deformation rates over time and provide insights into the effectiveness of backfilling in reducing creep deformations.