Centrica Energy said it extended its contract for the Hummingbird Spirit floating production, storage and offloading unit to March 2016.
Hummingbird Spirit is operating in the Chestnut field about 124 miles northwest of Aberdeen, Scotland, in the central waters of the North Sea.
The company said its overhaul of the field means it should be able to produce more oil than expected.
"The field was initially expected to produce around 7 million barrels of oil over three years," the company said in a statement Monday. "However, work undertaken by Centrica Energy means that the Chestnut field is now expected to produce significantly more, with recoverable reserves estimated to be around 18 million barrels."
Chestnut is currently producing around 7,000 barrels per day. The company said extended production shows it has been able to find the right strategy to optimize recovery from the North Sea.
The British government is looking for alternative energy resources because of the steady maturation of North Sea oil fields.
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