Forties is normally the largest or second-largest of the five crude grades that underpins Brent, loading as many as 15 cargoes in a month. The other four grades are Ekofisk, Oseberg, Troll and Brent itself.
"It's going to be a tiny programme," one of the sources said, adding that the Hound Point terminal where Forties cargoes load would be closed for most of June.
The wide Brent-Dubai price spread deterred Asian buyers from purchasing more Atlantic Basin oil priced off Brent and capped spot premiums of regional grades.
Petroleum Brunei has sold its Kimanis crude cargo loading in early June at $1.10 a barrel above dated Brent, while ConocoPhillips sold its cargo likely to Ampol at a premium of $1.30 a barrel, a trader said.
The Organization of the Petroleum Exporting Countries and allies led by Russia, a producer group known as OPEC+, are heading for a largely technical meeting next week in which major changes to policy are unlikely, Russian Deputy Prime Minister and OPEC+ sources said.