State-controlled Norwegian oil company Equinor has begun production at its $7.7 billion Mariner heavy oil development in the UK northern North Sea, about two years behind original plans.

First output flowed late last week, Equinor announced.

“It is a huge milestone to be ready for start-up,” said Hedda Felin, Equinor's outgoing senior vice president of UK & Ireland offshore, who is taking on a new role as an advisor to Equinor chief executive Eldar Saetre after three years in Aberdeen.