螺杆泵采油系统杆柱的扭转振动特性分析

摘要

对直井中用于驱动井下螺杆泵的旋转级次抽油杆柱建立了扭转振动分析模型，推导出了该级次抽油杆柱扭转振动频率的计算公式，建立了级次杆柱扭振固有基频与单级杆柱固有基频之间的关系。计算表明,泵深在700～1800m时，常用的二级抽油杆柱组合的扭振固有基频为22～58r/min,低于螺杆泵的工作转速区，这完全不同于有杆泵抽油系统。指出,由于螺杆泵采油系统的工作转速区高于其杆柱扭振固有基频，在选定螺杆泵采油系统的工作转速时，除考虑杆柱的基频外，还应考虑杆柱的扭振高次谐波频率，这样可以避免系统工作在高次谐波共振区，而且有利于避免系统工作转速在穿越高次谐波对应的转速时系统的失速；在设计螺杆泵采油系统杆柱组合时，应考虑组合杆柱对杆柱扭振基频的提高，尤其要注意常用的二级杆柱组合时杆长比接近50%的情况。%In this paper it makes a twisting vibration analysis model of therotary sucker rod string,which is used to drive the progressing cavity pump in vertical well，and deduces the calculating formula of the sucker rod string's twisting vibration frequency.then sets up a relation between sucker rod string's twisting vibration natural base frequency and single sucker rod's natural frequency.According to the calculation,the twisting vibration base frequency of common two-staged sucker rod string is from 20～58 rpm when pump is working within the depth of 700～1 800 m,which is below the working speed of progressing cavity pump,and it is completely different from the sucker rod pump oil production system.The paper points out that because the working speed of progressing cavity pump oil production system is higher than the twisting vibration base frequency of its sucker rod string,when we choose the working speed of the system,it is necessary to consider the base frequency as well as the high harmonic frequency of the sucker rod string,therefore we can keep the system from working within the resonant frequency region,and it is of advantage to be not out of control when the system's working rotary speed is through the high harmonic's speed.Designing the sucker rod string combination of the progressing cavity pump oil production system,we should take account of the increase of the sucker rod string's twisting vibration base frequency for sucker rod.Especially speaking,we should take more attention to the condition of the common two-staged sucker rod string when the two-staged sucker rod string's length ratio is about 50%.