Potential influences of leakage through a high permeability path on shallow aquifers in compressed air energy storage in aquifers

The potential leakage influences of compressed air energy storage in aquifers, especially on the overlying shallow aquifer environment, need more attention, but there is still a lack of relevant studies. In this research, a coupled wellbore-reservoir underground anticline model is simulated using T2Well/EOS3. Two-phase non-Darcy flows, different from the multiphase Darcy flow in porous media, are considered in both the central working wellbore and a highly permeable leakage path. In an anticline, the results show that the leakage rate will decline and reach a relatively steady state as the cycles continue. The final continuous small periodic oscillations of leakage rate occur with a hysteresis effect with respect to cycle injection-production. When air leakage occurs in the initial gas bubble process, it gradually disappears and gets replaced by brine leakage. A decrease in the reservoir permeability can result in a larger initial leakage rate, but a smaller rate and fluctuation during the cycle process. However, in a horizontal reservoir, strong gas fingering increases the risk of air leakage, which, once occurs, can last during the rest of the process. This research can deepen the understanding of the leakage process and help evaluate and prevent incidents of environmental contamination in gas storage in aquifers.