Global benchmark Brent crude LCOc1 was down 39 cents at $46.56 a barrel at 0917 GMT. It closed Tuesday 5.7 percent higher on news that members of the Organization of the Petroleum Exporting Countries would renew efforts to limit production.
U.S. crude CLc1 was 47 cents lower at $45.34 a barrel, Reuters reported.
"Prices are down on the build in U.S. crude oil stocks reported by the API last night," said Tamas Varga, oil analyst at London brokerage PVM Oil Associates.
Weekly U.S. crude oil stocks surged by 3.6 million barrels last week, the American Petroleum Institute (API) industry group said, exceeding analyst expectations of a 1.5-million-barrel rise.
The news dampened a rally infused by news that OPEC members were meeting ahead of an official group gathering on Nov. 30 to build consensus for a deal to limit production, and by oil pipeline attacks by militants in Nigeria.
A number of energy ministers from OPEC countries are likely to meet informally in Doha on Friday to try to build consensus over decisions taken by the full group in September in Algiers, an Algerian energy source said. [L8N1DH1KK]
"We estimate the possibility of an actual OPEC production cut as 50-50," said Hans van Cleef, senior energy economist at ABN Amro.
"If OPEC would stick to its intention to set its production ceiling at 32.5 million barrels a day, or even lower, market optimism will likely pick up, which could be supportive for oil prices."
The Dutch bank lowered its oil price forecasts on Wednesday, expecting Brent and U.S. crude to average $50 a barrel in the fourth quarter.