Lateral Vibration Simulation Of Sucker Rod String In Directional Well And Arrangement Optimization Of Centralizer

With the increasing difficulty of oilfield exploitation,more and more directional well are used in oilfield to production petroleum,and the phenomenon of eccentric wear of rod and tube in directional well becomes more and more serious.In order to reduce the phenomenon of eccentric wear of rod and tube,centralizer is installed to transform eccentric wear of rod and tube into friction between centralizer and tubing in every oilfield.At present,the configuration method of the centralizer is regard the rod column between two adjacent centralizers as the straight rod column,and calculating the maximum lateral deflection of the rod column by using the static method of the sucker rod column.However,the effect of the alternating load at the plunger pump on the lateral vibration of the rod string on the bending deformation was not considered,and the bending deformation rule,the contact state and the contact pressure of the rod string in the tubing were not studied in depth.For this reason,this paper conducts further research and analyzes the design method of lateral vibration characteristics of the rod string in directional wells and the configuration spacing of the centralizer.This paper mainly carries out the following work:Firstly,the complete hole trajectory was simulated based on the measured data of directional wells,and the two-dimensional hole trajectory data of directional wells were obtained.The environmental load of the rod string in directional wells was analyzed and simplified.Secondly,the mechanical model and mathematical model of transverse vibration of simply supported beam under alternating load are established.Using finite difference method to solve the fourth-order nonlinear partial differential equation,the influence of various factors on the maximum displacement of transverse vibration under axial alternating load is analyzed.The transverse maximum displacement under the action of static load and alternating load is compared.It is concluded that the transverse maximum displacement under axial alternating load is smaller than that under static load.Again,finite element analysis model of rod string is established,considering the axialalternating load and damping on the influence of transverse vibration,establishing the overall transverse vibration model of rod string,the dynamic characteristics of lateral vibration of sucker rod string under axial alternating load are obtained.The transverse vibration characteristics of rod string under finite element method are compared with those obtained by differential equation,and the lateral vibration of whole sucker rod string under alternating load is displayed intuitively.At last,the existing arrangement method of sucker rod string centralizer is introduced,and according to the transverse vibration characteristic of the whole sucker rod string under alternating load,the new arrangement method of sucker rod string centralizer and the constraint condition of arrangement optimization are put forward.