Feasibility analysis of using closely spaced caverns in bedded rock salt for underground gas storage: a case study

A closely spaced caverns design for large-scale underground gas storage (UGS) is proposed, in which four caverns compose one group. The pillar widths between adjacent caverns are 0.7D in the same group and 1.5D between different adjacent groups (D is the maximum diameter of the cavern). Caverns in the same group operate with the same injection–production mode to decrease the negative effects of running parameters on the pillar safety. Thicknesses of salt between the cavern and the upper and lower mudstone layers are about 15 m. To verify the design, a three-dimensional geomechanical numerical model is built by ANSYS software, taking into account Jintan salt mine strata characteristics, mechanical behavior properties and running of the UGS, to monitor the deformations and stresses of the model. The deformations, volume shrinkages, plastic zone extension and configuration, equivalent strain, and safety factor are studied with the three-dimensional geomechanical numerical model. The results obtained by the numerical simulations and the model experiments show that the three-dimensional geomechanical numerical model has a high accuracy, the safety of the closely spaced caverns UGS can be ensured under different running conditions, and the proposed design has a good feasibility. This design can double the number of caverns of the original design and provide additional storage capacity of about 10 × 104 m3 for a single cavern. This approach can be implemented for similar projects in other places.