The Movement And Vibration Numerical Simulation Of Sucker Rod String In Fluid Of Oil Pipe

Aimed at low system efficiency and high energy consumption of the oil pump well, the modulus of elasticity to the sucker rod is changed to match the swabbing parameters of the rod-pumping well in this article, so that it can reduce the input power of electromotor to decrease the dynamic load, and increase the throw of pump to increase the well yield. Besides, vibration characteristic of the sucker rod in oil pipe and the cushioning principle have been researched systematically in order to improve system efficiency.Taking the dynamic theory as a foundation, dynamic model of the sucker rod is established, and the geometry non-linearity, contact non-linearity and structure dynamics are combined organically. Taking use of the hydrodynamics, the frictional coefficient between downhole equipment pump and well liquid of the sucker rod pumping system is taken as the boundary condition of the sucker rod has been deduced, and the finite element model is established. Using the Newmark method to resolve, the working condition of the sucker rod in oil pipe has been simulated actually, the cause of vibration and influencing factor, the changing rule between modulus of elasticity of sucker rod and its vibration frequency, as well as the rule between the polished rod load and the stroke of pump are researched.According to cushioning principle and vibration characteristic of the oil pump well, beginning with the physical, chemical, mechanical and structural characteristics, the cushioning device with different materials and structures are chosen and designed. The indoor rigidity test, damping test, and the life test experiment are carried on. Also, material and structure of the cushioning device have been confirmed basing on tentative data and the actual working condition of the sucker rod.According to real data from the scene, the empirical formula of the sucker rod vibration period is revised. The initial vibration point of the sucker rod is researched from the theoretical calculation as well as the indoor experiment. Taking this as the foundation, combined with the vibration theory, the mathematical model between the rigidity and vibration coefficient has been established. The relation between rigidity and vibration reduction, as well as the relationship between energy saving and the stroke of oil well pump are inferred theoretically. Analog computation is carried on using the above results and the finite element method, which has confirmed the correctness of the theoretical derivation. The influence of the material parameters (rigidity and damping) to the polished rod load and throw of pump has been calculated, and has laid the theoretical foundation to the actual operation.In order to examine the accuracy and the usability of this method, the cushioning devices are installed on the sucker rod of the pump well. As the fore-and-aft effect indicates, the system efficiency rises 3.8%, and the average electricity saving rate is 9.7%, which has confirmed the correctness and rationality of this design. The results demonstrated that using cushioning device to increase system efficiency referred in this article has certain practical significance and value.