The Vibrational Characteristic Analysis Of The Rod String In Screw Pump Well

The screw pump oil extraction system has gotten more and more extensive application in the oil field for its advantages, which include simple structure, wide adaptability and remarkable energy saving effect etc. As the matter of fact these advantages haven't been fully played because of the imperfection of screw pump product and the related technology. Along with the generalization application of heavy displacement screw pump, the vibration of the screw pump system becomes the increasingly outstanding problem.There are mainly three vibration types of screw pump rod string: torsional vibration, lateral vibration and vertical vibration, which the first two vibration forms have relative serious impact on oil production. Torsional vibration has greatly affected the efficiency of the screw pump system, and the rod instable rotation with vertical vibration would significantly reduce or instantaneous disappear the preload of screw connection, which may cause the screw thread trip under small anti-twisting moment. The most noteworthy problem is lateral vibration caused by rod instable rotation, which is a main factor of rod eccentric wear. Therefore, the vibration analysis of the screw pump rod string has important theoretical and practical meaning.In this paper, based on summing up the force of the screw pump rod string, take the effect rotary inertia of ground-driven and transmission system on rod torsional vibration into consideration, improved the mechanical model and the calculation methods of natural frequency, established natural frequencies calculation formula of single class,double classes and triple classes assembled rods torsional vibration, analyzed single class rod steady-state response under harmonic excitation of drive head load and pump load. Analyzed the lateral vibration of the rod string. Calculated the natural frequency of sucker rod system, took the vibration into consideration, adjusted the scope of rod string rotary speed so that it can avoid rod resonance. Analyzed the effect of damping, stress, rod-column structure on the systemic frequency.This thesis has laid foundation for better solving the problem of rod eccentric wear and optimizing screw pump system, which has certain guiding significance to the on-site practice.