A North Sea development expected to produce up to 70,000 barrels of oil per day has begun operations.
Nexen’s Golden Eagle Area Development, which incorporates three separate fields, is predicted to reach peak production in 2015.
Meanwhile, two of the North Sea’s oldest facilities, Brent Alpha and Brent Bravo, ended their productive lives on Saturday.
Li Fanrong, chief executive of Nexen owners CNOOC, said: "The project was delivered on schedule, on budget, and to world-class safety standards. It supported in excess of 2500 jobs in the UK and makes a significant production contribution to the company in the near future."
UK oil firm Maersk holds a 31% stake in the Golden Eagle development.
Martin Rune Pedersen, Maersk Oil UK managing director, added: “Today’s announcement represents a great achievement by the Golden Eagle project teams.
"A project of this scale is important for the UK North Sea and for Maersk Oil. To deliver it safely, on time and on budget is an excellent performance.”
The Golden Eagle area is located around 43 miles north east of Aberdeen and includes the Eagle, Peregrine and Solitaire fields. The development is currently producing around 18,000 barrels of oil per day.