Abstract: During injection-production operations of underground gas storage facilities,frequent pressure fluctuations disturb the in-situ stress field and may induce fault reactivation,seriously threatening sealing integrity.To solve this problem,a simulation model of underground gas storage in a depleted gas reservoir was established based on fluid-solid coupling mechanisms;the dynamic evolution of formation parameters under cyclic injection-production was analyzed;and the impacts of injection-production rate and injection-production location on fault stability were investigated.Results show that during injection-production of underground gas storage,pore pressure and effective stress at the fault location corresponding to the injection-production well change significantly under cyclic injection-production.The reservoir top and the fault-projection position corresponding to the injection-production well constitute high-risk areas prone to fault slip.Higher injection-production rates and smaller distances between injection-production locations and the fault lead to greater pore-pressure increase in the reservoir,more likely disturbing the stress field near the adjacent fault and increasing the risk of fault slip.This study provides a theoretical basis for fault-stability evaluation and optimization of injection-production processes for underground gas storage facilities.

Key words: underground gas storage facility, fluid-solid coupling, fault stability, stress perturbation, fault slip, numerical simulation