Operating Electrical Submersible Pumps (ESPs) below the perforations offers multiple advantages and in some cases, can change field production economics feasibility. For example, lowering the intake below all perforations reduces gas interference for better pump performance while also maximizing the well drawdown. Induction ESP motors however rely on well fluid moving past the motor for motor cooling and for this reason ESPs have been installed either above the perforations or have utilized mechanical means to divert well fluid across the motor when installed below the perforations. Diverting the fluid to pass by the motor involves the use of special devices such as shrouds or circulating tubes which adds complexity to the equipment configuration and can negatively affect both performance and runlife.
This case study is about a well that has proven too challenging for conventional ESP technology due to its high gas/oil ratio and unusual production profile. Multiple conventional ESP installations, set above the perforations, using induction motors (IM) failed shortly after installation and were unable to maintain continuous production. A permanent magnet motor (PMM) ESP system was successfully installed in this well below the perforations without a shroud. It minimized gas locking of the pump and increased daily production.
Many operators and ESP providers have tried to install ESPs driven by induction motors below the perforations in the past without the use of a shroud or a circulation tube, but in most cases the motor heat rise could not be maintained within operating limits. The authors believe that the ESP deployment/operational method in this well is the first commercial successful electrical submersible pump installation without forced heat convection (through shrouds or circulating tubes) and would like to share their experiences with this application as this new technique will improve ESP operating conditions in many wells.