Coupled nonlinear wellbore multiphase flow and thermo-hydro-mechanical analysis of compressed air energy storage in aquifers

Compressed air energy storage in aquifers (CAESA) is a low-cost large-scale energy storage technology. To study the mechanical influence of the reservoir on CAESA, a coupled nonlinear wellbore multiphase flow and thermo-hydro-mechanical simulator, THMW-Air, is developed and verified to be effective using data from the pilot CAESA project in Pittsfield. The hydrodynamic, thermodynamic, and mechanical behaviors, as well as the energy efficiency of CAESA, are analyzed and compared using the T2Well-EOS3 simulator, which does not include the mechanical processes. Results show that, by incorporating the mechanical effects of the reservoir, the correlation coefficient between simulated and monitored pressures in Pittsfield improves from 0.9046 to 0.9211. The effective stress in the aquifer of CAESA decreases by 2.0 MPa and the permeability increases by at least 14.1 %. By considering the geomechanical effects, the air migrates farther horizontally, and the increase in temperature and pressure is relatively smaller. When the air injection temperature is 50 °C, the rate of decrease in energy efficiency under the THM condition is 9.75 % higher than that under the TH condition, while when the air injection temperature is 20 °C, the rate of increase in energy efficiency under the THM condition is 5.15 % higher than that under the TH condition.