Influences of groundwater on air tightness and surrounding rock stability of CAES underground gas reservoir

The tightness and stability of compressed air energy storage (CAES) gas reservoir is the basis to ensure the safe operation of power station. There are many factors affecting the mechanics of gas reservoir and its mechanics characteristics are complex. The accurate prediction and evaluation of reliability and stability in the long-term operation process has always been an important topic. Based on the thermodynamic model for compressed air considering the leakage and heat transfer process as the unsteady boundary and the theory of thermo-hydro-mechanical coupling as the core, a joint analysis model for gas storage is established under the coupling of multiple physical fields. The influences of groundwater in the rocks around the cave on the air tightness and stability of gas storage are studied. The results show that: (1) The existence of groundwater can reduce the gas loss per cycle in gas storage by 78%. (2) The lining structure is mainly subjected to tensile stress, and the stress concentration appears at the top and bottom, where more steel bars is suggested to be configured. (3) The existence of groundwater in rock mass is helpful to strengthen the gas sealing effects in gas storage.