Two-phase flow simulation of water scaling of compressed air storage under cyclic pressure change in an unlined rock cavern

Numerical simulations of two-phase flow through a porous medium were performed to understand the dynamic behaviour of the air that seeped out of an unlined cavern adopted for CAES (Compressed Air Energy Storage) in a saturated rock mass. In some cases, the pressure in the cavern is expected to change periodically due to daily or weekly usage of the compressed air. When the pressure is lowered, the amount of groundwater flowing into the cavern increases. If the water supply is insufficient, the air leakage might be induced. This study also investigated the effects of the periodic change in the air pressure on the water sealing of compressed air. It was found that the air which had seeped into the porous rock mass was trapped in a definite zone around the cavern when the pressure in the cavern was lowered.