Numerical Determination of the Optimized Shape of Salt Caverns for Gas Storage

Using salt caverns is one of the most developed methods for fluid hydrocarbon storage. Certainty of caverns stability and simultaneously having an economical working gas ratio, are important factors that rarely have been considered in Iran. Considering salt rock characteristics and high overburden, the gravitational stress can be assumed dominant. In situ stress acts as an external pressure and causes cavern convergence. Since conventional rock supports e.g. shotcrete, rock bolt, etc. are not applicable in the salt caverns; the cavern stability can only be achieved by an internal pressure caused by the gas inside the cavern. The paper deals with salt cavern stability analysis for gas storage. Specific geometrical and geotechnical properties (with the general properties of salt domes located in the Southwest of Iran) have been modeled by Phase2 and FLAC3D softwares. Geometrical and mechanical modeling of these caverns in finite difference and finite element in desired depth, determined the minimum and maximum gas pressure for cavern stability and working gas pressure was calculated as well. Comparison of these results implies that carrot shape cavern is more economical.