The Brent field in the Northern North Sea is enjoying an extended life partly due to installation of electrical submersible pumps (ESPs) to back-produce water from the reservoir. ESPs have been deployed with some success to prolong reservoir depressurisation in order to replenish the gas cap for subsequent production.

This is the first offshore application of ESPs for this purpose and differs from water production from aquifer wells for reinjection purposes. Moreover it has not been achieved without overcoming technical challenges such as minimal control during start-up, the use of fixed-speed drives, operating high horsepower motors, and a large degree of sub- surface uncertainty.

The equipment selected for the ESP system is described, including downhole and topsides equipment. An extensive development and testing programme was undertaken to qualify the pump and motor design for this unusual duty.

Lessons learned from the testing, commissioning and operational phase of the project are discussed.

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