Barrier Fluid-Less, Subsea Seawater Injection Pump Qualification

Abstract The objective of this paper is to demonstrate the successful qualification of a 3.0MW canned motor pump for subsea seawater applications via wet-pit testing. The canned motor topology ensures high reliability by eliminating the need for a barrier fluid system and mechanical seal. This topology uses the process fluid as the lone lubricant and cooling media in the motor resulting in an all-electric seabed barrier fluid-less pumping system for the subsea injection of treated seawater into a reservoir. To qualify canned motor technology for deployment subsea, a full-scale, 3.0MW canned motor water injection pump was tested in a wet-pit to demonstrate a Technology Readiness Level (TRL) of 4 per API 17Q. Pump performance was characterized across the entire operating speed range with a suite of instrumentation, recording parameters including flow, differential pressure, casing and rotor vibration, winding temperatures, and electrical parameters. The test program encompassed operation across a wide spectrum of envisioned conditions including over-speed conditions, cyclic testing, emergency shutdown conditions, and endurance testing at full load. Qualification was achieved via evaluation of the test results and post-test inspection of key components, including bearings. Canned motor pumps have a demonstrated track record for more than 50 years in various critical applications. This development and qualification program demonstrates how this technology has been adapted to serve as a subsea barrier fluid-less motor-pump system and its potential to optimize field economics through an all-electric power distribution system. The paper will demonstrate qualification unit performance and reliability under simulated operating conditions and transients. Presented data will show performance meets predictions, how the unit showed no observed change over time during replicated lifetime of service cycles, and endurance testing results. Inspection results, to be shared, showed all major components in good working conditions and that the bearings demonstrated no indications of rubbing or contact. These results support qualification to a Technology Readiness Level (TRL) of 4 per API 17Q, which has been endorsed by several end users who followed testing and reviewed the data. The implementation of a canned motor pump to this subsea application results in a non-conventional, barrier fluid-less pumping system creates the potential to optimize field economics. Elimination of the mechanical seal and barrier fluid increases reliability and prevents process water contamination. This topology also enables economic saving through removing the need for topside hydraulic power units (HPU), hydraulic lines in an umbilical, and enabling an all-electric subsea architecture including permitting longer step-outs. The canned motor topology is scalable and flexible, with demonstrated reliable operation in topside applications up to 5.5 MW, and utilized in pumping applications with multiphase fluids and highly abrasive solids.