A Preliminary Design of cavern for Underground Compressed Gas Storage in Ardebil City using Flac3D Software

Today، natural gas storage in underground is received much attention. It is a fundamental technique to control consumption particularly during the cold months of the year. For this purpose، several methods are used for underground storage of gas، such as reservoirs، aquifers، salt caverns، rock caverns (lined or unlined) and abandoned mines. Each of these methods is selected according to the geo-mechanical and hydro-mechanical characteristics of the region such as permeability، porosity، aquifer level، compressive strength and tensile strength of rocks، and internal pressure of stored gas. In this research، based on the geological، hydrogeological and geo-mechanical conditions prevailing in Ardebil area، the best method was selected. Primary studies have indicated that storage in both lined and unlined rock caverns is possible. The cavern has 235 and 81m burden for unlined and lined design respectively. However، lined rock cavern has priority in this area. A numerical approach was used for analyzing the stability of storage cavern. There are not many discontinuities in the area therefore FLAC3D was selected for numerical analysis. The results of the analyses showed that the induced strains around the lined cavern before and after gas injection appeared to be less than the critical strains calculated by Sakurai’s relation. Therefore، the storage cavern should be stable and gas storage at this cavern is possible with 2 MPa internal Pressure.