Coupled hydro-mechanical analysis of underground gas storage at Sarajeh field, Qom formation, Iran

Abstract

Production or injection of fluids from/in an underground storage site causes variations of pore pressure and stress states. These fluctuations significantly affect implications for hydraulic fracturing, wellbore integrity, top surface subsidence and heave, fault-reactivation, and stability of reservoir and caprock. Therefore, in order to keep optimal conditions during the process of gas injection and production, it is of paramount importance to have accurate estimates of the pore pressure. In this investigation, coupled fluid flow and geomechanical simulations, as well as rock mechanical tests, are performed on the Sarajeh field, Iran to investigate the geomechanical behavior of the Sarajeh reservoir during gas injection and production as well as estimate the caprock and reservoir integrity and evaluate the risk of fault reactivation. The results show up to −16 cm subsidence due to the production and 6 cm heave due to the injection. The critical pressures for the reservoir rock's failure and activation of the faults are 11,283 psi and 9986 psi, respectively, which make the operator able to store gas up to 2.2 and 1.9 times higher than the maximum reservoir pressure. Hydro-mechanical evaluation of the Sarajeh field determines essential information about the effect of gas injection and production for safe and successful seasonal gas storage.