Objective Compressed-air energy storage in salt caverns is a key solution for addressing fluctuations in power supply from grid-connected renewable energy sources, and the long-term operational safety of the underground storage facilities is crucial to its viability. Open-hole intervals are uncased wellbore sections within salt rock, and are directly subject to the coupled effects of high-frequency cyclic injection–production pressures and salt-rock creep. Their stability is a core factor affecting the sealing performance and injection–production efficiency of the storage facilities. However, quantitative understanding of the long-term deformation evolution of open-hole intervals under high-frequency cyclic loading remains insufficient, and failure mechanisms and instability risks in multi-well coordination cases are not well understood, leaving a limited and unreliable basis for safety spacing design.

Methods This case study investigates a representative salt-rock block using physical and mechanical parameters of the rock mass derived from geological stratification data and laboratory rock-mechanics tests. A three-dimensional geomechanical model was built in Rhino to reproduce the daily cyclic operating conditions of a power station in China. The model was then imported into FLAC3D for long-term numerical calculations over a 30-year period. A parametric study compared the evolution of the plastic zone, displacement field, and stress field in the surrounding rock for open-hole spacings of 5 m, 10 m, 15 m, and 20 m.

Results The long-term deformation of open-hole intervals exhibits significant anisotropy: axial tension dominates (cumulative axial strain over 30 years: 0.8％), while radial contraction prevails (cumulative radial strain over 30 years: 0.2％); salt-rock creep was identified as the core driving mechanism. Plastic-zone development shows lithology-dependent behavior: interlayers are dominated by shear failure, whereas salt rock layers are dominated by tensile failure. Initial stress concentrations at the salt-rock/interlayer interfaces are gradually relieved as creep progresses. Spacing analysis indicates that, at 5 m spacing, the plastic zones of adjacent open-hole intervals fully connect, creating a high-risk pathway for coordinated instability among wells; at spacings of 10 m and greater, the plastic zones remain isolated and overall system stability is markedly improved.

Conclusion This study identifies a long-term deformation mechanism for open-hole intervals under high-frequency cyclic loading—axial tension dominance and creep driving—and a differentiated failure mode of shear in interlayers and tensile in salt rock. Based on plastic-zone connectivity analysis, a 10 m spacing is proposed as the recommended design threshold for open-hole interval safety under the study area’s conditions. This value represents the lower mechanical safety limit for the long-term stability of the surrounding rock and can serve as a basic constraint for decisions such as drilling design and wellhead layout. Physical model experiments and on-site monitoring are required to further refine the evaluation methodology.