Canned Motor Pump Development and Validation for Subsea Caisson Boosting Applications

Abstract This paper will present the general design features and associated testing to validate a 1750 HP canned motor pump (CMP) as an alternative to traditional electric submersible pumps (ESP) for the production of oil and gas in subsea caisson applications where reliability is essential. The CMP development aimed at designing a robust solution that eliminates typical failure points of submersible pumps and validating the design to demonstrate its readiness for deployment. The CMP is a seal-less topology that has been employed in other critical applications including radioactive slurry and commercial nuclear applications. This fit for purpose caisson CMP was engineered and manufactured to meet the operating conditions for a specified offshore application. The CMP development included mockups to validate materials, design features, manufacturing processes, and performance. The full CMP system testing was performed in water at the vendor's test facility and with 2 to 300cP viscosity, multiphase fluids at the end user's test facility. CMP validation was achieved via evaluation of the test results and post-test inspections on key components, including bearings. Typical caisson ESPs have a run life of approximately 2.5 years. Root cause failure analyses (RCFA) on these systems have shown a majority of failures resulting from the seal and motor. The main function of the seal section is to protect the motor from contamination by the process fluid. Once the seal section is compromised, the motor becomes susceptible to failure modes due to degradation of dielectric fluid. The seal-less CMP system eliminates need for a mechanical seal or seal section by isolating the wound stator from the process fluid with a corrosion resistant liner. An outcome of this configuration is that all bearings must operate in the process fluid. Presented data will include results from thrust bearing testing in multiphase fluid to demonstrate robustness in wide varying conditions in addition to performance testing from the full CMP system testing in water and multiphase fluids. Post-test inspection results of key components will be presented to support the conclusion that the CMP system is ready for deployment. The canned motor pump (CMP) for caisson applications is a non-conventional alternative to typical ESPs through the elimination of the seal section and use of process lubricated bearings. This paper will share features, learnings, and results that demonstrate the canned motor pump technology is ready for deployment in a subsea ESP caisson application.