The Analysis Fluid-solid Coupling Vibration And Safety Evaluate Of Completion String Of High Gas Well

The completion string is an important channel connecting the formation and the ground.During the production of high-production gas wells,when the high-speed fluid flows through the string,the vibration of the string is induced,and the vibration of the string will affect the gas flow and form fluid-solid coupling vibration.Vibration can cause the fatigue failure of the string and reduce the sealing performance of the coupling thread,and increase the wear of the string.Therefore,it is very important to study the fluid-solid coupling vibration of the completed pipe string to ensure the safe production of the oil and gas field.To the completion string as the object of study object,The main work of this paper is as follows.Firstly,the causes and influencing factors of the vibration of the completion column are analyzed,and the calculation model of temperature,pressure,density and flow velocity of gas in the well string of high gas production wells is established.Secondly,using the equations of motion and the continuity equation of the fluid and the vibration equation and the constitutive equation of the solid is used to derive the fluid-solid coupling vibration equation of the completion string.The equations are decoupled by the characteristic line method and the discrete solutions are carried out by spatial interpolation method.Considering the influence of the switch well on the vibration of the completion string,the fluid-solid coupling vibration of the completion string is analyzed and discussed in the case of emergency shut-off and normal shut-off.Thirdly,simulating the well conditions and the modal analysis of the completion string is analyzed by the finite element software,the influence of different pressure,temperature and axial force on the natural frequency of the pipe string is discussed.The results show that the natural frequency of the completion string increases with the increase of the axial force,and decreases with the increase of the internal pressure,and the temperature has no effect on the natural frequency of the completion string.The modal analysis of the fluid-filled pipe string shows that the fluid-solid coupling will reduce the natural frequency of the completion string.Finally,the deformation mechanism and failure form of the completion string are discussed,in order to study the aspects of string design and field construction technology,the reasonable suggestions are put forward for the safe production of oil field.