During 2012, BakerHughes, ConocoPhillips and Nexen Inc. continued their research partnership [Waldner 2011] with a new experimental test program focused on the thermal performance of Electric Submersible Pump (ESP) systems for Steam Assisted Gravity Drainage (SAGD) applications, which was completed in the high-temperature flow loop at C-FER Technologies.
Accurately monitoring the internal temperature of the ESP motor is a key consideration when trying to increase the operational longevity of an ESP system for any application; however, as the SAGD process develops, understanding this temperature profile has become more critical. This test program included several tests at various fluid temperatures and ESP operating conditions that helped determine the thermal performance of the ESP motor. Another unique aspect of this test program was the incorporation of two different temperature monitoring methods at approximately the same position on the internal and external base of the ESP motor: one internal probe positioned near the motor windings via a fiber optic sensor and one external skin temperature RTD positioned on the motor surface to monitor this important temperature differential.
This paper presents the equipment and instrumentation used, and demonstrates some of the more interesting test results, thus providing further insight into the thermal performance of this ESP motor under representative SAGD conditions between 220ºC (428ºF) and 250ºC (482ºF).
ESPs are presently the most widely used downhole mechanical lift method in SAGD production wells. Due to the added complexity and high cost of SAGD well interventions, the longevity of ESP systems has become a critical consideration when balancing well economics. At the same time, ESP technology has been pushed toward more challenging conditions such as operating with produced fluid temperatures of up to 250ºC (482ºF) and operating at very low intake pressures near the steam saturation curve.
The reliability of submersible systems is strongly dependent upon the internal temperature of the ESP motor, meaning the expected run time of the ESP system can be significantly shorter when operating at higher fluid temperatures where motor insulation capabilities are often reduced. For this reason, the ability to monitor the ESP motor temperature (and make appropriate operational adjustments) has become extremely important when striving to maximize longevity. ESP manufacturers have made some significant progress during the past few years to increase the internal temperature ratings of ESP motors, especially in material temperature ratings. This has included collaborating with operators to test new high-temperature systems and working to optimize performance and reliability throughout a broad range of operating conditions [Noonan 2010] [Waldner 2011] [Medina 2012].