Study on the Fatigue Failure Law of Gas Storage Caprock Under Periodic Injection and Production

Whether qualitative or quantitative, whether macroscopic or microscopic, Predecessors' research on the sealing ability of caprocks is concentrated on the static model of the caprock. A few scholars have also proposed the sealability evaluations of the caprock dynamic evolution process, they are all aimed at the dynamic evolution of geological historical periods, and there are few studies on the sealability of gas storage caprocks under periodic injection and production. In this paper, the characteristics of stress and strain under alternating loads of rock and non-rock materials are investigated and experimentally studied to clarify the law of fatigue failure of gas storage caprocks under periodic injection-production. The results show that it is possible that the microcracks may develop and propagate in the rock after the gas storage has experienced many periodic injections and productions, when the stress is far less than the rock strength limit, And then a macroscopic deformation is formed. The accumulated plastic deformation of the rock will increase, and the plastic deformation rate will gradually decrease, as the number of injection and production increases.