Research On Rod Torsion Buckling And Centralizer Placement Of Progressive Cavity Pump

In the operation of Progressive Cavity Pump,the slender sucker rod in the oil pipe subjected to torque is prone to torsion and buckling,which causes the sucker rod to contact with the oil pipe and easy to cause rod and pipe eccentric wear.Taking the sucker rod in the oil pipe as the research object,the torsional buckling behavior and centralizer placement of the sucker rod are studied by dynamic relaxation method.It is found that the torsion rod without centralizer will buckle and make a large area of contact with the tubing.The influences of the number of centralizer and the clearance ratio of spacing sucker rod diameter tubing on the torsion and buckling of sucker rod are studied.The clearance ratio is the only factor affecting the dimensionless torque,which increases with the decrease of clearance ratio.The fitting formula of sucker rod clearance ratio and dimensionless torque is obtained,the critical length curve of sucker rod is drawn according to the fitting formula and the condition of satisfying allowable shear stress,and the critical length of sucker rod with various diameters under common clearance ratio is enumerated.After installing centralizer,the critical length of sucker rod at any depth of well is reduced by 25% compared with that without centralizer.The critical length of sucker rod at the bottom of wellhead was increased by 45% compared with that without centralizer.In order to avoid the eccentric wear of rod and tube caused by torsional buckling deformation,the research results in this paper can provide theoretical guidance for the placement spacing of rod centralizer in Progressive Cavity Pump.