Theories And Technologies To Prevent Eccentric Wear Between Sucker Rod And Tubing

Eccentric wear is the main problem in the latter production period of oilfield when the water cut is high. Crooked hole and rod buckle are important reasons for this problem.The paper studied the buckle behavior of sucker rod in different constraint conditions, built rod buckle differential equations, and the equations were sloved by energy variational method, obtained the configuration function of sucker rod after sine and helix buckle, the contact force function between rod and tube, and the critical load function of rod buckle;On the foundation of 3D well track, this article took friction, inertial force and elastic force into consideration, established a 3D mechanical model which is used to describe the stress condition of sucker rod, this model is solved by finite difference method;The text studied the influences of the production parameters and production condition to rod stress. The influence factors include sucker parameters, water cut, pumping fluid level and so on. This part of study can be used to guide the proper choice of production parameters, in order to slow down the rate of eccentric wear;Because of the difference of vertical well hole and 3D crooked well hole, two design models are established on the basis of slender pressure lever theory and flexed beam theory separately; the additional resistance forces caused by the centralizers are drived, and the stress condition of sucker rod are analized after the centralizers are installed;Computer programs are compiled using VB program language, three models realized computer calculation by programming: the 3D mechanical model of rod stress, the design model of rod centralizer interval and the analysis model of rod stress after centralizers are installed. These programs are powerful tools to simulate rod stress, to determine the location of eccentric wear between rod and tube, and to design proper interval of centralizers.