Objective To address the extremely low utilization rate of thin salt beds in horizontal salt cavern gas storage in China—caused by brine gravity differentiation—a novel three-step solution mining technology featuring “vertical–horizontal–inclined” cavity construction is proposed. This approach aims to overcome dissolution limitations at the cavity bottom through the lateral scouring effect of the inclined section and to establish a comprehensive geomechanical evaluation system for the entire life cycle, thereby providing theoretical support to enhance the efficiency, safety, and reliability of gas storage.
Methods Drawing on the engineering similarity criterion, large salt rock specimens were used for physical simulation tests of multi-step cavity construction. Three-dimensional laser scanning and the mirror symmetry method were employed to reconstruct the cavities obtained in the tests, enabling analysis of morphological characteristics and expansion patterns in the vertical, horizontal, and inclined sections. Based on the test-derived cavity morphology and the geological features of the Jintan salt bed, a three-dimensional geomechanical numerical model at engineering scale was developed to assess the long-term stability and economical efficiency of horizontal salt cavern gas storage.
Results The physical simulation tests confirmed the effectiveness of the new technology, with the dissolution efficiency of the inclined section 18％ higher than that of the horizontal section. The unique lateral scouring effect increased the proportion of dissolved salt rock at the cavity bottom below the drilling trajectory from a negligible level to 35％. Numerical simulations indicated that the cavity volume shrinkage rate over time exhibited three distinct stages, with a cumulative 30-year value of 16.52％, well below the 30％ safety threshold. Maximum surrounding rock deformation reached 3.12 m, concentrated at the cavity top. The dilatancy safety factor of the surrounding rock remained mainly between 3.0 and 5.0, meeting engineering safety standards. However, simulations also revealed local stress concentrations at interlayer interfaces due to elastic modulus differences, resulting in high-risk areas where the dilatancy safety factor fell below 1.0, indicating a need to improve the stress path by optimizing cavity morphology.
Conclusion The established “test–model” verification framework demonstrates the dual advantages of the three-step cavity construction technology in enhancing both salt bed utilization and cavity stability. By innovation in dynamic mechanism, this technology achieves a 26％ increase in single-cavity expansion for gas storage in thin salt beds, setting a new paradigm for high-efficiency energy storage facility construction.
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