Stability evaluation and economic analysis of four-well interconnection salt cavern hydrogen storage-A case study of Huai'an, China

Salt cavern hydrogen storage (SCHS) is considered a critical pathway for achieving large-scale hydrogen reserves in the future. To fully utilize existing salt cavern resources and enhance the stability and economic efficiency of SCHS facilities, this study takes the Huai'an salt mine in China as an engineering background to propose a four-well interconnection salt cavern hydrogen storage model based on the reconstruction of existing caverns. Through numerical simulation and economic analysis, the effects of cavern roof depth and injection-withdrawal cycle frequency on the four-well interconnection model were explored. The results indicate that, within a roof depth range of 1000 m–2000 m, maintaining the minimum operating pressure (Pmin) and maximum operating pressure (Pmax) at 0.3 and 0.8 of the vertical stress of the overlying strata (σz), respectively, the stability of the cavern decreases with increasing depth, while increasing the injection-withdrawal frequency (IWF) helps to enhance stability. At roof depths of 1600 m, 1800 m, and 2000 m, it is recommended to increase Pmin to 0.35 σz, 0.4 σz, and 0.45 σz, respectively, to enhance stability further. The four-well interconnection model achieves the maximum gas storage capacity and the lowest levelized cost of hydrogen storage (LCHS) when the roof depth is approximately 1400 m, indicating optimal economic performance. The findings of this study provide guidance for the reconstruction of existing salt caverns and large-scale hydrogen storage development.