A New Evaluation System for Feasibility and Stability Analyses of Ultra-Large Salt Caverns Gas Storage

Based on traditional evaluation indexes, i.e., displacement, volume shrinkage, and equivalent strain, a new safety evaluation system, including the dilatancy safety factor (DSF) of bedded salt rock and failure approach index (FAI), is proposed in this work. Taking the Jianghan gas storage as the engineering background, the feasibility and stability of ultra-large underground gas storages (UGSs) in the Jianghan plain are demonstrated through this evaluation system. A 3D numerical model is implemented based on geological survey results and mechanical parameters of the Jianghan salt district. Subsequently, preferred geometric diameter and operating parameters, including cavern diameter, allowable pressure range, gas production rate, safety pillar width, and operation mode, are determined through a wide range of simulations. Results show that the suitable diameter is 80 m, the allowable pressure range is 16–34 MPa, the reasonable gas production rate is 0.5–0.6 MPa/d; a safe pillar width should be 2–3 times the cavern diameter, and the preferred operating mode should be synchronous injection–production mode. The simulation results, showing a high consistency with the previous research results, indicate the effectiveness and reliability of the proposed evaluation system. This work provides an alternative solution for the safety assessment method and design purposes for the UGSs in bedded salt rock.