Harbour Energy has started production at the Tolmount gas field in the British North Sea, a source close to the company said on Monday.
Harbour operates and holds a 50% stake in the field along with Dana Petroleum.
The field, whose start-up was initially planned for the first quarter of the year, is expected to reach peak production of 40,000 barrels of oil equivalent per day (boed).
Harbour Energy took ownership of the field as part of its takeover of North Sea rival Premier Oil last year. Its output will help Harbour reach its 2022 production target of between 195,000 and 210,000 boed.
The company downgraded Tolmount's reserves earlier this year.
Tolmount's start-up was first reported in a note by Jefferies analysts.
(Reporting by Ron Bousso, Editing by Louise Heavens)