Electric submersible pumps (ESPs) are widely used for high volumetric oil and gas recovery from downhole wells. ESPs in oil fields can be equipped with multiple ac motors in tandem. To assist a motor start-up, a solid-state soft-starter can be deployed in such ESP wells. ESP shafts have a long axial length, and thus experience significant dynamic torsion when started from reduced voltage soft-starters. Premature shaft breakdowns had occurred in the field during the motor start-up for soft-starter fed ESPs. This paper investigates the shaft breakdown phenomenon in a 750-HP ESP system using a real-world case scenario. A lumped parameter electro-mechanical model for the ESP system is developed to observe its dynamics. The effects of static as well as fluctuating torsional stress on the interconnected pump shafts are analyzed to determine the root cause of the shaft breakdown. Criteria for successful start-up for soft-starter driven ESP systems are also presented to increase the equipment's operational life.

中文翻译：

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软起动器潜水电泵系统的轴故障分析

潜水电泵（ESP）广泛用于从井下井中大量采油和采气。油田的ESP可以串联安装多个交流电动机。为了帮助电动机启动，可以在此类ESP井中部署固态软启动器。ESP轴具有较长的轴向长度，因此从降低电压的软启动器启动时会遭受明显的动态扭转。对于软起动器馈电的ESP，在电动机启动期间，现场发生过早的轴故障。本文使用实际案例研究了750-HP ESP系统中的轴故障现象。开发了ESP系统的集总参数机电模型，以观察其动力学。分析了互连泵轴上的静态应力和波动的扭转应力的影响，以确定引起轴故障的根本原因。还提出了软启动器驱动的ESP系统成功启动的标准，以延长设备的使用寿命。