[Editor's note: This story was updated at 10:18 a.m. CST Oct. 2]

Norway's Equinor ASA (NYSE: EQNR) confirmed on Oct. 1 it had agreed to buy Chevron Corp.'s (NYSE: CVX) 40% stake in the Rosebank oil field west of Scotland's Shetland islands for an undisclosed sum, as Chevron shrinks its North Sea presence.

Chevron is also looking into selling its other assets, most of which it operates, in the British North Sea.

RELATED: Equinor Reportedly Eyes Chevron's Stake In Rosebank Field

Rosebank, one of the largest undeveloped oil and gas fields off Britain, is situated some 130 km (80 miles) northwest of the Shetland Islands and could hold more than 300 million barrels, Chevron has said.

The complex project is currently estimated to cost over $6 billion, according to consultancy Wood Mackenzie.

Equnior UK Asset Map (Source: Equinor ASA)

"We look forward to becoming the operator of the Rosebank project. We have a proven track record of high-value field developments across the North Sea and will now be able to deploy this experience on a new project in the U.K.," Equinor said.

The other partners in the field are Suncor Energy Inc. (NYSE: SU) with 40% and Siccar Point Energy with 20%. Siccar Point is seeking to sell at least half of its stake.

Reuters reported on Sept. 28 that Equinor was interested in buying Chevron's stake, citing sources close to the process. Equinor, known as Statoil then, had sold its stake in Rosebank to OMV in 2013.

The sale of the Chevron stake to Equinor is subject to customary conditions, including partner and authority approval, with completion targeted as soon as possible, Equinor said.

The San Ramon, Calif.-based company kicked off a sales process for its North Sea oil and gas fields Alba, Alder, Captain, Elgin/Franklin, Erskine and Jade as well as the Britannia platform and its satellites, it said in July.

A spokeswoman said the marketing of these assets was still in the early stages and it was too soon to say whether they would be sold or not.

Chevron also holds a nonoperated stake alongside BP Plc (NYSE: BP) and Royal Dutch Shell Plc (NYSE: RDS.A) in the Clair Field in the British North Sea.

"Selling its stake to Equinor could spell the end for Chevron in the U.K. and Europe. It has already moved on from Norway and Denmark, and is looking to offload its U.K. North Sea assets," WoodMac's upstream analyst Kevin Swann said.

"If all the sales go through, it would leave Clair as its only U.K. asset, the 19.42% stake is valuable, but may not be enough for Chevron to retain a U.K. presence ... We believe Equinor sees an opportunity to re-scope [Rosebank] and reduce costs. It has done similar work on Norway's Johan Castberg."

Chevron has in recent years focused its efforts on rapidly growing its shale production in the Permian Basin in Texas as well as the giant Tengiz Field in Kazakhstan.

Chevron's net daily production in the North Sea in 2017 averaged 50,000 barrels of oil and 155 million cubic feet of natural gas, according to its website.