Patent ID: 8740586

Claim:
A method for cooling a motor for use in an electrical submersible subsea booster pumping system, the method comprising: positioning a conduit having first and second ends subsea; mounting a submersible pump assembly in the conduit, the pump assembly having a centrifugal pump, an electrical motor, and a seal section connected between the pump and the motor, the motor being filled with a dielectric lubricant; connecting a cap to one of the ends of the conduit; providing a submerged heat exchanger external of the conduit in a vicinity of the sea floor, the heat exchanger having an inlet port and an outlet port; connecting a dielectric lubricant inlet line to the inlet port of the heat exchanger, extending the inlet line sealingly through the cap to the submersible pump assembly in fluid communication with the dielectric lubricant in the motor; connecting a dielectric lubricant outlet line to the outlet port of the heat exchanger, extending the outlet line sealingly through the cap to the submersible pump assembly in fluid communication with the dielectric lubricant in the motor; flowing production fluid into one of the ends of the conduit and operating the motor, causing the pump to pump production fluid out the other of the ends of the conduit which is connected to a production flow line or riser; circulating the dielectric lubricant from within the motor through the inlet line to the inlet port of the heat exchanger; removing heat from the dielectric lubricant at the heat exchanger by exchanging the heat with seawater to thereby reduce the temperature of the dielectric lubricant; circulating the dielectric lubricant from the outlet of the heat exchanger through the outlet line into the motor; and with the seal section, reducing a pressure differential between the dielectric lubricant in the motor the hydrostatic pressure of the production fluid in the conduit outside the motor.