Analysis Of Contact Wear Of Rod String And Tube In Vertical Well Pumping Unit

The problem of eccentric wear of rod string is always the key problem in the field of oilfield engineering.At present,it is generally believed that the buckling instability of sucker rod string in tubing string is the root cause of partial wear,and the economic loss caused by the sucker rod breaking and oil pipe leakage caused by the eccentric wear of the rod tube is huge.On the one hand,the eccentric wear of sucker rod increases the number of pump operation,on the other hand,it reduces the production of oil well.On the basis of establishing the simulation model of the environmental load of sucker rod string,using the finite element method studies the buckling problem of sucker rod string.Based on the interface technology of Visual Basic and ANSYS,developing the software for the simulation of the contact state of rod string.The research results of this paper lay the foundation for the further study of the rod and tubing wear of the vertical sucker rod pump.In this paper,the influence of the axial force,the inertia force of the sucker rod string,the buoyancy of the sucker rod string,the friction between the sucker rod and the well fluid,the concentrated load at the pump end and the concentrated force at the hoop are considered,and the simulation model of the environmental load and the mechanical model of the sucker rod string are established.Based on stability theory study,compressive bar buckling model is established;Based on the finite deformation theory,the geometric nonlinear equations and contact nonlinear equations of sucker rod string are established,and the boundary condition equation is also given.With the three-dimensional beam element for technical support,a sucker rod buckling load simulation model based on ANSYS is established considering the structural stiffness and geometric stiffness matrix of the impact on the unit,and then using eigenvalue method and nonlinear method solve the sucker rod buckling critical load and buckling mode under the uniform load.In the ideal conditions of sucker rod buckling,the helical buckling simulation model is established under the uniform load on sucker rod.Based on the finite element method,the simulation model of the contact state of the rod and tube and the simulation model of the transient dynamics of the sucker rod string in the oil well are established.The simulation results of contact state distribution and contact pressure distribution of sucker rod string under different conditions are given.Based on the Visual Basic and APDL language,the simulation software for the contact state of the rod string is developed,The parameterized modeling method and batch method can greatly simulate and calculate the contact problem of the rod string in oil field.It can be used to calculate the critical axial pressure,the contact pressure of rod and tube and the eccentric wear of rod and tube.