Analysis And Experimental Research On Fluid-solid Coupling Vibration Characteristics Of Gas Production Tubular String

The gas production string is the only channel for oil and gas resources to be mined from underground to the surface.In the process of natural gas production,the damage of gas production string often occurs,especially in high temperature,high pressure and high yield gas wells.The fluid structure coupling vibration of the string is one of the main reasons for this problem.This paper first introduces the basic theory of fluid structure coupling vibration of pipe string,in which the state equation of natural gas and the vibration model equation of pipe string are introduced,the 4-equation mathematical model of fluid structure coupling of pipe string is derived,and the characteristic line method is used to solve it.Then,the fluid structure coupling system of ANSYS Workbench software is used to simulate and analyze the fluid structure coupling vibration characteristics of the gas production string.The simulation results show that when the natural gas production is constant,the greater the natural gas pressure in the string,the smaller the natural gas flow rate,the greater the density,and the more severe the string vibration;When the bottom hole pressure is constant,the greater the flow rate of natural gas in the string,the greater the flow velocity and density of natural gas,but the change range of density is small,and the string vibration is more intense;When the fluid parameters remain unchanged,increasing the axial tension at both ends of the string can reduce the radial vibration amplitude of the string under fluid structure interaction;The vibration of buckling string is more severe than that of straight string under fluid structure interaction.Secondly,the fluid structure coupling vibration of the simulated pipe string under the influence of four variables is studied through indoor simulation experiments.The experimental results show that the amplitude of the simulated pipe section is larger at the moment when the inlet valve or outlet valve is opened or closed due to the influence of water hammer effect,expansion effect and other factors;The larger the axial tension on both ends of the simulated pipe section,the smaller the amplitude in each direction and the higher the natural frequency of the simulated pipe section when the gas passes through;The results show that the sand and liquid in the gas flow in the experimental section cause greater vibration amplitude of the experimental section.Finally,according to the experimental situation and a large number of literature research,a more perfect fluid structure coupling vibration test-bed is improved and designed.In the actual production process of natural gas wells,it is necessary to formulate reasonable production planning,control the maximum production of gas wells,ensure stable production as far as possible,reduce the sudden change of fluid pressure and velocity,appropriately increase the string tension at the wellhead,and regularly carry out drainage and desanding operation for water producing and sand producing gas wells,which can reduce the severe degree of fluid structure coupling vibration of the string and ensure the safe and reliable production of gas wells.At the same time,the fluid structure coupling vibration experiment of pipe string is of great significance for the study of the vibration behavior of gas recovery string,and it is urgent to design and build the fluid structure coupling vibration experiment platform of pipe string in line with the actual working conditions.