BP has announced first oil from the 20 million barrel Alligin field, west of Shetland.
Alligin has been developed as a two-well subsea tieback to the Glen Lyon floating, production, storage, offloading vessel (FPSO).
It was originally forecast to produce 12,000 barrels gross of oil equivalent a day at peak.
But BP said Alligin started up in late December and had managed to deliver 15,000 boe per day.
The project included new subsea infrastructure, consisting of gas lift and water injection pipeline systems, and a new controls umbilical.
Operator BP has a 50% stake in Alligin and Shell has the remaining 50%.
BP North Sea regional president Ariel Flores said: “Achieving first oil from the Alligin field safely, under budget and ahead of schedule is testament to the performance of the project team and their agile approach to planning and execution.
“Alligin is part of BP’s advantaged oil strategy, a development with a shorter project cycle time with oil that is economic to produce and low risk to bring to market.
“Subsea tiebacks like this complement our major start-ups and help underpin our growing portfolio west of Shetland.”