Airtightness evaluation of compressed air energy storage (CAES) salt caverns in bedded rock salt

Abstract

CAES technology provides large-scale clean energy storage of electric energy and enhances the spatio-temporal structure of power generation and utilization. The airtightness of salt caverns is essential for the economic viability of CAES systems. In this paper, a thermo-hydro-mechanical (THM) model is proposed for assessing the airtightness of CAES salt caverns in bedded rock salt. The accuracy of the model was verified using field data. Furthermore, the permeability and porosity of the rock salt and interlayer in the target cavern section were measured based on the Yunying salt district as the engineering background, and a 3D geomechanical model was established. The variations in temperature and pressure in the cavern were analyzed. Meanwhile, the seepage range, pore pressure, safety factor, and leakage amount of the JD5 and JD6 well groups under different cases within 1 year of operation were explored. The results indicate that the permeability magnitudes of rock salt and interlayer are on the order of magnitudes of 10⁻¹⁸ m² and 10⁻¹⁹ m². The interlayer serves as the primary channel for air leakage. When the permeability of the interlayer is lower than 1 × 10⁻¹⁸ m², the percentage of air leakage from the CAES salt cavern is less than 1 %, and the JD5 and JD6 well groups exhibit excellent airtightness. When evaluating the airtightness of CAES salt caverns, the mass percentage of air leakage, pore pressure, and stability are recommended to be considered together. This study provides references for future airtightness evaluations of CAES projects in salt caverns.