Phase-to-phase communication scheme for downhole monitoring tool design in electrical submersible pump systems

Electrical Submersible Pumps (ESPs) are commonly used in deep wells in oil and gas industry. In order to monitor ESP systems operating conditions, downhole monitoring tools are used to transmit data representing physical conditions of downhole such as temperature, pressure, and vibration to the surface. The most common downhole communication method implemented in the field is to use a DC signal over three phases of the main power cable and uses the ground as a return path. However, this method cannot operate in the event of a single-phase-to-ground fault, because the signal path would be shorted although the electrical submersible pump is still in operation due to the ungrounding practice in downhole ESP systems. Experience has also shown that this existing method is prone to failure in presence of unbalance conditions in the system. In this paper, a new phase-to-phase communication scheme for the downhole monitoring tool design is proposed where intentional disturbances in the power supply to the motor are used as means of binary communication. The proposed scheme is immune to single-phase-to-ground faults and unbalance conditions. Theoretical formulas defining this method are developed and the performance of the method is evaluated using simulation through case and sensitivity studies.