Improving the accuracy of salt cavern gas storage site selection by considering macro- and micro-scale geologic body attributes

To overcome the high misclassification rates of storage-class designation (traditional methods achieving <60% accuracy) and incomplete coverage of evaluation criteria encountered in current salt cavern gas storage site selection evaluation schemes, a multi-indicator assessment system was constructed. This system comprises six macroscopic geological variables---rock salt-bed burial depth, halite-bearing formation thickness, salinity (soluble fraction), NaCl content, gas-storage capacity, and interbed thickness—and four microscopic geologic parameters---fracture toughness of salt, caprock permeability, caprock porosity, and rock-salt triaxial strength. By macroscopically analyzing salt-deposit structure, fault systems, and caprock sealing integrity, and by microscopically characterizing the physicochemical and mechanical properties of target halite, the Analytic Hierarchy Process (AHP) was employed to assign criterion weights. Coupled with a grey-target model that computes the comprehensive target-center distance (TCD) for each candidate site, this approach effectively resolves the limitations of scant or incomplete criteria and low classification accuracy inherent to conventional site-selection practices. Results indicate that Jintan salt cavern, exhibiting the minimum TCD (0.45), emerges as the optimal site, and its storage-class designation achieves 100 % concordance with the actual construction sequence. The proposed methodology furnishes a quantitative decision-support tool for pre-feasibility SCGS siting, offering significant engineering guidance for the rational exploitation of halite resources and the efficient, integrated utilization of salt caverns.