关键词: 螺杆泵, 抽油杆, 碰撞接触, 动力学分析, 有限元法

Abstract: In order to design the rod string and analyze failure mechanism, the dynamics analysis on rod string of surface driving screw pump must be conducted. A nonlinear dynamics model for describing the impact contact state between rotating rod and tube was presented. In consideration of the impact contact between rotating rod and tube that happens in any direction of well depth and well bore circumference, the dynamic gap element to describe the random impact contact state between rotating rod and tube was constructed. A rotating rod dynamics analysis method was proposed by combining the dynamic gap element with space beam element. This method has been applied to the B2-6-41 Well in Daqing Oilfield. It is shown that the relative error between calculated average value and actual test value of the rod torque at well head is 1.5 percent. The dynamic strength of rod string and the mount position of centralizer were calculated, according to the acquired deformation of rod string and its impact contact force with tube in the time domain. The designed rod string with this method can safely run in the well for longer time, which makes pump-inspection period over 550 days. This method can also be widely used in other Oilfields.

Key words: screw pump, rod string, impact contact, dynamics analysis, finite element method