Mechanics Properties Simulation Study On Sucker Rod String Of Surface Driving Screw Pump

The screw pump oil extraction system has gotten more and more extensive application in the oil field for its advantages, which include simple structure, less initial investment of equipment, remarkable energy saving effect and wide adaptability, etc. Compared with pumping units, pump detection period of the screw pump oil extraction system is relatively short, Its main reason is the failure of sucker rod string, especially the high viscosity well and the polymer flooding well ,which greatly frustrates the operation of the screw pump oil extraction system. Therefore, researching on the mechanical analysis of sucker rod string has important theoretical significance and practical application value. This paper will mainly carry out the following aspects:The simulation model of friction pressure drop of power law fluid in oil pipe, friction load, friction torque of sucker rod string are established in this paper. The simulation analysis of pressure drop of friction load and friction torque are changing with revolving speed, the ratio of rod and tubing diamete changes in power law fluid and Newton laminar flow. The simulation results show that rheological property of produced fluid have significant influence on friction load.On the basis of space beam element model of sucker rod string, considering the impacts of screw pump rotor eccentricity and centrifugal force of eccentric rotating sucker rod string on its bending distortion, centrifugal force softening stiffness is brought in to modify the stiffness matrix of beam element by using dynamic-static method; application two-directions spring to imitate the contact status between sucke rod string and oil pipe, and considere impact of boundary constraint because of the difference diameter between rod and coupling. Integrating beam element with two direction spring element, Static finite element simulation model on sucker rod string of surface driving screw pump was established. Considering the axial vibration, torsional vibration and lateral vibration of sucker rod string in surface driving screw pump well comprehensively, dynamic finite element simulation model on sucker rod string of surface driving screw pump was established.Using Visual Basic 6.0.to develop " finite element mechanical properties simulation software of sucker rod string with surface driving screw pump ". the software functions include: external load calculation of sucker rod string; simulation the bending deformation of sucker rod string within oil pipe, the contact position and the size of the contact force; analysis node displacement variation with time. The software to provides technical means.for the mechanism study on eccentric wear of sucker rod string, measure of anti-eccentric friction design and sucker rod string strength design.