Analysis of Gas Phase Fluctuation Pressure in Oil Pipes During Production and Shutdown Operations of Gas Storage

To optimize the production and shutdown operations of gas storage, reduce the gas phase fluctuation pressure of oil pipes and avoid fatigue failure of valve cores and oil pipes caused by impact loads, a mathematical model of gas phase fluctuation pressure in the oil pipes for production and shutdown operations of gas storage was established by considering the gas phase compressibility, flow velocity, pressure wave velocity, and other factors. The model was established based on the conservation equation of mass and momentum, and the model was solved by the method of characteristics programming. With Well H2 of Hutubi gas storage as an example, the effects of factors such as daily gas production, depth and inner diameter of oil pipe, shutdown time, and gas volume of gas storage well on the fluctuation pressure of oil pipe were analyzed. As the shutdown time prolonged, the peak fluctuation pressure decreased, and the time to reach the peak increased. As the inner diameter of the oil pipe decreased, the daily production increased, and the shutdown time decreased. The fluctuation pressure showed an increasing trend. Compared with a daily production of 50×10⁴ m³/d and 600×10⁴ m³/d, the maximum peak fluctuation pressure at the wellhead decreased by 10.05 MPa, and the maximum fluctuation pressure at the bottom of the well decreased by 4.01 MPa. The research shows that the mathematical model for the gas phase fluctuation pressure of the oil pipe has high accuracy, it can provide assistance for the production and shutdown operations of gas storage.