Prices have been volatile during the holiday-shortened final week of 2015 and remained near multi-year lows in the face of indications a global crude supply glut will continue into next year.
US benchmark West Texas Intermediate for delivery in February was down 68 cents at $37.19 and Brent crude for the same month was trading 41 cents lower at $37.38 a barrel at around 0620 GMT.
Analysts expect US commercial crude stockpiles in the week to December 25 to have declined when the Department of Energy releases the data later Wednesday, but Bloomberg News said that would still leave supplies more than 120 million barrels above the five-year seasonal average.
US oil production is expected to remain above 9.1 million barrels per day, which would bring little respite to the crude oversupply that has suppressed prices for more than a year, analysts said.
“The inventory data is likely going to be the most important set of news that we would be seeing this week,” Daniel Ang, an analyst with Phillip Futures in Singapore, said in a market commentary.
“Most likely, production would disappoint us and remain above 9.1m barrels/day,” he added.
At a meeting earlier this month, the Organization of the Petroleum Exporting Countries effectively rejected calls for output cuts to boost prices.
Iran is also expected to ramp up its oil exports after Western economic sanctions are lifted next year as part of a deal reached in July to curb Tehran’s nuclear programme, further exacerbating the supply and demand imbalance.