Large-scale compressed air energy storage (CAES) systems offer an efficient solution to mitigate the intermittency of renewable energy sources, yet ensuring the airtightness of underground lined caverns under groundwater influence remains a major technical challenge. In this study, a governing equation for gas–liquid multiphase flow was developed based on the relationship between capillary pressure and saturation, incorporating the effects of temperature and gas pressure variations on saturation. Building upon this, a thermo–hydro–mechanical (THM) coupled two-phase seepage model was established to simulate the coupled evolution of thermal, hydraulic, and mechanical fields in lined CAES caverns. The model enables integrated analysis of pressure, temperature, saturation, and deformation, revealing the mechanisms by which groundwater affects the sealing and stability of the system. Simulation results show that groundwater significantly enhances airtightness by suppressing gas leakage, stabilizing operation pressure, and improving thermal–mechanical equilibrium. Under groundwater conditions, the peak leakage rate decreased by 36.8%, and cumulative leakage was reduced by 47.7% after 60 cycles; the daily leakage percentage fell below 1% after five cycles, meeting sealing requirements. Groundwater delays pore pressure dissipation, induces mild pressure hysteresis, and maintains a stable deformation amplitude of about 4–5 mm within the allowable range. The gas–water interface migrated radially up to 8.2 m from the cavern wall, exhibiting a nonlinear–linear transition governed by permeability and capillary effects. The developed THM framework provides a robust and unified tool for evaluating multi-field coupling processes and optimizing the airtightness and design of lined CAES caverns in water-rich geological formations. • A new two-phase flow model of CAES cavern is obtained, which is suitable for predicting gas–water migration. • A unified simulation method for gas–liquid seepage and sealing performance of CAES caverns is established. • Groundwater enhances cavern airtightness by maintaining pressure and reducing gas leakage.
Jiang et al. (Sat,) studied this question.