Fluid-solid Coupling Vibration Characteristics And Experimental Study Of Fracturing String Considering Friction Effect

As the main load-bearing component and power transmission component,fracturing string is under gravity,internal and external fluid pressure,axial force,friction force and other loads during construction.These actions are easy to induce the vibration of the string,and make the stress,deformation and motion of the string very complex.At the same time,the vibration of the string reacts the flow of the fluid,thus forming a two-way fluid structure coupling vibration.Therefore,on the basis of considering the friction effect of the fracturing string,this paper analyzes the fluid solid coupling vibration characteristics of the string,and carries out laboratory verification experiments,including the following contents:The main transient parameters of the flow field are calculated by FLUENT software,and the change of the flow conditions that cause the vibration of the pipe string is obtained.Considering the friction coupling effect between the pipe wall and the liquid,the fluid-solid coupling dynamic model of the fracturing string is established based on the incompressible liquid motion equation,continuity equation,vibration equation and constitutive equation of the solid,and the axial vibration response of the fracturing string is solved by the transfer matrix method.Using AUTOPIPE software to simulate and analyze the laboratory string with 1:1 model,considering the influence of the change of fracturing fluid property on the fluid solid coupling vibration characteristics of the string,focusing on the analysis of the influence of the change of fracturing fluid displacement and pressure on the fluid solid coupling vibration characteristics of the string.Finally,the vibration of the fracturing string is analyzed through the actual simulation conditions.The results show that: When the liquid flows through the coupling part,bending part and inclined part of the fracturing string,due to the sudden change of the cross-sectional area of the string or the change of the flow direction of the liquid,the flow pressure and flow speed of the liquid will change,and the string is more likely to vibrate;the high-speed fluid will intensify the vibration of the fracturing string due to the increase of the dynamic pressure;the boundary pressure and speed of the flow The instantaneous change of the fracturing fluid will intensify the axial vibration of the string;the change of the fracturing fluid property will also have an impact on the fluid solid coupling vibration characteristics of the fracturing string;with the increase of the fracturing fluid displacement,the vibration speed and amplitude of the string will increase,and the vibration acceleration at the midpoint of the string is greater than that at the inlet,and the larger the fracturing fluid displacement is,the acceleration of the vibration of the string at the midpoint and the inlet will be The greater the degree difference.The research results of this paper can provide reference for the combination of string,selection of pipe material and selection of construction parameters.