A Study On Transverse Vibration Of Rod Strings Under The Condition Of Buckling Excition In Vertical Wells

The rod string is one of the core components of the rod pumping system.Due to bending of the rod string caused by the constraint of oil tube and various loads,rod strings wear eccentrically because of the connection between rod strings and oil tubes when the sucker rod reciprocates from top to bottom in the vertical wellbore,which affects the service life of the sucker rod and could lead to the accidents of rupture of the rod body in the extreme condition.Therefore,it is very significant to study the law between the force and deformation of sucker rod string in oil pipe,accurately predict the contact area and contact pressure of rod string and oil tube for the design of anti-eccentric wear in the oil well.This paper mainly carried out the following aspects:(1)deeply studying the simulation model of the plane static buckling for rod string and improving the simulation algorithm for solving the buckling configuration of sucker rod.The specific contents include: considering the working pressure in the pump barrel and the liquid load on the pump end,the simulation model of sucker rod with axial distribution force is established.The difference equation and finite element equation for the buckling configuration of sucker rod are established based on the actual structure of sucker rod string.This paper presents a method used for solving the dynamic characteristics of sucker rod string to solve the buckling configuration of sucker rod.(2)Deeply studying the simulation model of plane dynamic buckling for rod string,solving the inherent characteristic of transverse vibration of sucker rod,and applying Flouent theory to solve dynamic stability region and the critical frequency of the rod string,which lays a foundation for the further study of sucker rod string dynamic response under the environmental load.(3)Applying the difference method and finite element method to solve dynamic response of transverse vibration for the rod string under the conditions of initial buckling excitation,environmental loads and the constraint of oil tube,ascertaining contact area and contact pressure between the rod string and tubing,which lays a foundation for the design of anti-eccentric wear in the oil well.