North Sea Forties crude differentials rose for a third day on Friday as the May loading schedule showed a drop in supplies from this month.
The supply of North Sea crude that underpins the Brent benchmark will average 774,000 barrels per day (bpd) in May, according to loading schedules provided by trade sources on Friday, down from April.
Planned maintenance at Oseberg will reduce supply of that grade to two cargoes, or 39,000 bpd, while supply of Forties will also be lower, trade sources said.
No deals were done on Friday as traders assessed the May loadings, but bids were higher.
Refining margins remained at healthy levels, according to Reuters models, giving end-user crude demand some support.
The Brent market structure was also more bullish as doubts in the market about a swift return of Libyan supplies intensified.
The front of the forward curve had briefly flipped into contango on Wednesday on expectations that rebel-held Libyan ports would soon reopen, but it was in a near 10 cent backwardation on Friday. <LCOc1-LCOc2>
The Libyan government said it had seen evidence of "good intentions" at indirect talks with eastern rebels, which could lead to renewed exports, but that a deal has still not been done.
In the Platts window, Shell bid for a cargo loading April 20-23 at dated Brent plus 35 cents and for another cargo loading April 24-27 or April 28-May 1 at parity to dated Brent.
That was up from the last deal on Thursday when Mercuria bought from Vitol for loading April 17-19 at dated minus 15 cents.
(Reporting by David Sheppard; editing by Jane Baird)