* U.S. major sold off all operated Norway assets in 2017
* Remaining portfolio thought worth around $3-4 bln
* Has opened a data room to test market interest(Adds Exxon Mobil spokeswoman, details)
OSLO, June 22 (Reuters) - Exxon Mobil is consideringselling all of the stakes it holds in oil and gas fields off theNorwegian coast, a spokeswoman said.
Two years ago the U.S. major - the world's largest oilcompany - sold its operated assets in the area. But it hasretained stakes in more than 20 other fields, includingEquinor-operated Snorre and Shell-operatedOrmen Lange.
"Following interest expressed by several parties, ExxonMobil has decided to open a data room to test the marketinterest for the upstream portfolio in Norway," Anne Fougnersaid, adding that no decision to sell had yet been made.
A number of private-equity backed firms, including Okea, and independent oil firms Aker BP and DNO, have this year said they were looking to buy moreassets on the Norwegian continental shelf.
Fougner's remarks confirmed a report in local newspaperDagens Naeringsliv. She declined to comment on the value of theassets, which the business daily quoted an unnamed industryexpert as saying could be worth $3-4 billion.
In 2017, Exxon Mobil's net production from fields off Norwaywas around 170,000 barrels of oil equivalent per day, accordingto its website.
Erik Haugane, Okea's chief executive, told Reuters this weekhe expected all oil majors except Norway's Equinor to exit theNorwegian continental shelf in a decade.
Another Norwegian oil firm, Det norske - controlled bybillionaire Kjell Inge Roekke - bought BP's Norwegianassets in 2016, with BP getting a 30% stake in the new company,Aker BP.
U.S. major Chevron transferred its last stake in aNorwegian offshore license last year, while ConocoPhillipsstill operates Ekofisk, the first major oil discoveryoff Norway.
(Reporting by Nerijus Adomaitis; editing by John Stonestreet)
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