A Study On Mechanism And Prevention Measures Of Eccentric Wear Of Rod And Tube In TT Oilfield

As the current effective oil production method,the rod production system is widely used in major oil fields.In this system,the eccentric wear of the sucker rod and tubing is always one of the problems that plague the oilfield.As the TT oilfield enters the later stage of high water cut,the service period of the rod and tubing in the wellbore is shortened to 30 days.It is urgent to solve this problem.Based on previous research results,this paper analyzes the main reasons for the eccentric wear of rods and pipes in high water-cut oil wells in TT Oilfield,and finds that the oil well scaling,the nature of the produced fluid,and the influence of well fluid flow on the force of the rod string after considering the coupling effect These three factors are the most important.Based on this,the influence of each factor on the force of the rod string is studied separately.Regarding the movement of the donkey's head suspension point as the law of sucker rod movement,the concentric annulus well fluid movement equation is derived from the N-S equation,the rod and tube annulus model considering the coupling is established,and the annulus fluid flow characteristics are numerically calculated;In the case of coupling effect and oil well fouling,a improved sucker rod mechanics model is established based on the annulus fluid motion equation,and the neutral point calculation formula is derived through the neutral point definition,and the influence factors of the neutral point location distribution are analyzed;At the same time,the method of combining differential equations and finite element software was used to study the buckling law of sucker rods below the neutral point,and it was found that the sucker rods in eccentrically worn oil wells were in a state of spiral buckling.Finally,based on the rod and tube eccentric wear mechanism,the method of descaling oil wells and installing centralizers for anti-wear treatment is proposed.The main elements and composition of the fouling substances are obtained through technical laboratory analysis such as scanning electron microscope(SEM)and X-ray diffraction(XRD).The organic phosphoric acid hydroxyethylene diphosphonic acid(HEDP)is selected as the descaling agent.After descaling,the position of the sucker rod neutral point moves down,and the field application effect is good;the installation spacing of the centralizer is derived from the critical instability buckling formula of the rod column.The length of the rod string that is no longer buckled is used as the inspection standard to measure the installation of the centralizer.The buckling length of the rod string before and after the measures is compared with the buckling length of the rod string before and after the measures are replaced by the on-site production data of the oil well.The application effect is obvious.