Ala Eddine Aoun, Nelson Ruiz, Jesica Pfeilsticker, and Kurt Cole
Baker Hughes
Electric Submersible Pumps (ESPs) remain one of the most widely deployed artificial lift technologies for maximizing production from Permian wells. Operating companies often find themselves installing ESPs between multiple producing zones or even below the perforated intervals for several reasons, including the goal of maximizing production by setting the pump as deep as possible and increasing natural gas separation to help stabilize operating trends.
Shroud and recirculation systems are the two primary technologies used for ESP motor cooling. In this paper, the performance of both techniques was evaluated, and the main challenges, limitations, and lessons learned are discussed.
A dataset comprising hundreds of ESP installations equipped with motor cooling systems was analyzed to evaluate the performance of both techniques. Survivability curves were used to compare the reliability of these systems, while several Dismantle Inspection and Failure Analysis (DIFA) reports were reviewed to identify the main failure mechanisms and root causes. Numerical simulation was conducted to better understand the physics underlying the recirculation system performance. Operating trends and production data were also examined to further assess the challenges, limitations, and efficiencies of these technologies.
Based on survivability curves, ESPs equipped with cooling systems demonstrated a 45% higher average runtime compared to standard ESPs. Over 400 ESPs with recirculation systems have been installed in the Permian Basin, with an average run life of 982 days and several wells exceeding 4,000 run days. Numerical simulation indicates that setting the pump below the perforations can achieve up to 95% natural gas separation, ensuring reliable and stable operation. In contrast, pull and DIFA reports show that units installed with shroud systems experienced several critical challenges and failures. These include incidents of holes in the shroud preventing proper cooling, scale and sand deposition inside the shroud reducing production rates, and in many cases causing complete blockage. Additionally, the pump stack inside the shroud often contributes to reliability concerns, making the shroud a less dependable option compared to the recirculation system.
The standardized industry practice for deploying ESP systems below perforations requires the use of a motor cooling system. This study demonstrates the superior reliability of the recirculation system compared to the shroud, providing the industry with best-practice guidance for future ESP installations.