Distribution Optimization Design Method Of Directional Well Centralizer Based On Rod Tube Contact State Simulation

As the core component of rod pump well,the sucker rod string is bent and deformed due to the constraint of the wellbore trajectory and the complicated environmental load when it is lifted in a directional well,makes the rod-tubing eccentric wear.Affected by the partial wear,the rod body is subject to the multi-axial alternating load and is prone to fatigue fracture,the coupling is easily damaged by the static strength,causing the lay-well and affecting the crude oil production.Therefore,on the basis of studying the stress of the sucker rod string in the tubing,establishing the optimal design method of the centralizer,it is of great significance to reduce the eccentric wear rate and improve the overall development benefit of the oilfield.This paper mainly studied the following aspects:Based on the orthogonal experiment method,using the Fluent-software to simulate the liquid friction load between the pump cylinder and the pump plunger and the hydraulic loss along the length of centralizer and sucker rod coupling,and the multivariate non-linear regression model of liquid friction between the pump cylinder and the pump plunger and the hydraulic loss along the length of centralizer and sucker rod coupling were established.Based on the theory of multiphase flow in wellbore and the movement rule of oil pump plunger,the simulation model of liquid load in oil pump were established.The mechanical model of statics simulation of directional well sucker rod was established.The “space beam element + spring element” finite element analysis model was established.The limit value of the contact pressure between the centralizer and the tubing was determined by the centralizer friction and wear test.Based on the finite element simulation calculation of contact state of the rod and tube,aimed at controlling the contact pressure of sucker rod body,coupling and centralizer,the optimization design method of directional centralizer was established.Based on energy wear theory,the wear prediction model of sucker rod column was established.Based on the geometrical model of sucker rod body and the wear of sucker rod coupling and centralizer,mathematical models of the friction and wear of the body,the sucker rod coupling and the centralizer were established.Considering the deformation and wear of the rod body,a calculation model of the multi-axial stress of the rod body was established.On the basis of controlling the contact pressure of rod and pipe and the maximum number of single rod centralizer,considering the wear life of rod string,a method for optimizing the distribution of centralizer in directional well was established.An optimal design system of directional well centralizer based on contact state simulation of rod and tube was established by VB,which can simulate the area and contact pressure of rod and pipe eccentric wear,and evaluate the anti-bias wear effect of centralizer,life prediction of sucker rod string and optimum design of centralizer in directional well.