Downhole Tool Design for Conditional Monitoring of Electrical Submersible Motors in Oil Field Facilities

The electrical submersible pump (ESP) systems rely on downhole tools to monitor the operation of electrical submersible motors and pumps. The monitored parameters include temperature and vibration of the motor, and the pump intake pressure. Transmitting these parameters successfully and reliably through a downhole tool from downhole to surface under various ESP system operating conditions is critical for production optimization and equipment safety. In this paper, a new downhole tool design method using a phase-to-neutral communication scheme is proposed, which can overcome issues of current downhole tool products installed in the field. In this design, an effective signal communication path is formed by external impedance on the wellhead connecting one phase to the ground combined with a controlled thyristor at downhole connecting the neutral of an electrical submersible motor to the ground. Extensive analytical calculation and PSCAD simulation of the proposed method are demonstrated in the paper. Two case studies are conducted using a real ESP system under normal and single-line-to-ground fault conditions. A sensitivity study is performed to evaluate the influence of various factors on the signal strength for signal communication purpose. A lab testing further provides proof of concept. The proposed method in this paper will result in a reliable and effective downhole tool design for an ESP system operation.