Research On Mechanics Of Sucker Rod String For Polymer Flooding Rod Pumped Well And Point Arrangement Optimization Of Centralizer

Polymer flooding is a kind of boosting way to flooding oil by injecting polymer into underground reservoir.After polymer output from polymer flooding rod pumped well(hereinafter referred to as "polymer flooding well"),the composition and viscosity of oil well fluid have a great change,which aggravates the partial abrasion of rod and wellbore,and seriously affects the production efficiency of oil field.Considering the rheological properties of well fluid,this thesis studied the mechanical behavior of rods in polymer flooding well,which lays a foundation for the design of sucker rod string against eccentric wear and the optimization of centralizer arrangement,and ensures the stable and high production of oil field.Considering the rheological properties of viscoelastic fluid produced in the wellbore of polymer flooding well,the governing equations of the unsteady viscoelastic fluid flow in eccentric annulus is established.Based on the velocity distribution law of fluid in eccentric annulus,an analytic model of viscoelastic fluid normal force of sucker rod string is established.The results show that when the rod is moving eccentrically in the viscoelastic fluid wellbore,the rod is subject to the action of the fluid normal force,and the normal force is affected by the factors such as stroke,stroke frequency and eccentricity.Considering the compressibility of the gas phase in liquid,the friction between the plunger and the pump barrel and the hydraulic resistance of the valve gap,the calculation model of concentrated axial load of plunger is established.Considering the influence of viscoelastic fluid damping force on the longitudinal vibration of sucker rod string,the simulation model of nonlinear longitudinal vibration,axial load and axial distributed load are established.The results show that both the axial load and the axial distribution load of rod vary with time and well depth.Based on the quasi-static method and considering the influence of fluid normal force on the flexural deformation of sucker rod string,an analytical model of the flexural deformation of the rod between adjacent couplings is established.Based on the space beam element and the movable spring element,the finite element simulation model for the flexural deformation of the sucker rod string in the wellbore is established,and the optimization method of centralizer layout is established based on the simulation of the flexural deformation of the rod.The results show that the fluid normal force has a significant effect on the contact pressure of the rod-tube,and the optimization method of centralizer layout can effectively prevent the rod-tube eccentric wear.