Traders saw Oman's premium to Dubai set at 36 to 45 cents for December, or slightly up or down from the 41-cent premium in the November OSP.
"Plus 40 cents may sound high but there were lots of trades at plus one," a Singapore-based trader said.
February-loading Oman crude was now sold out and no fresh numbers were heard for March crude with many traders away from their desks.
The Japanese markets will be closed on Thursday and Friday for public holidays, which looks set to further limit trading.
On the light sour market, Abu Dhabi, the biggest producer in Opec-member the United Arab Emirates, will supply full crude term volumes for February to at least four Asian refiners after cutting 10 percent off Murban term supplies for January, term lifters in Japan and South Korea said on Wednesday.
At least one refiner will receive 500,000 barrels of additional crude, but extra volumes for February will be limited, with several refiners saying they did not request additional volumes.
"We heard from them about February supplies, which will be full. It's good that February supplies are not affected," a Japanese refiner said.
Two refiners said they had yet to be notified of their February volumes while several others could not be reached.
Additional volumes were seen unlikely to exceed 2 million barrels.
The February Brent/Dubai Exchange For Swaps (EFS) traded at $3.90 on Wednesday evening, largely unchanged from earlier in the day, but 10 cents lower than Tuesday's assessment.
February Brent stood at $56.35 at 1058 GMT, down some 20 cents from around the same time on Tuesday.