U.S. crude oil surged on Wednesday, posting its biggest one-day percentage gain in more than two years.
The advance came a day ahead of the Brent February contract's expiration and on the day that options for the U.S. contract expire, brokers and traders said. Other analysts pointed to the dollar's weakness against a basket of currencies.
West Texas Intermediate crude for February settled at $48.48 a barrel, up 5.6 percent for the session, marking its best day since June 2012.
Brent reversed earlier losses to trade about 3 percent higher. February Brent crude was up $2.24, at $48.27 a barrel. The contract slipped earlier on U.S. crude stockpiles and weak World Bank growth forecasts.
Energy Information Administration data showed U.S. crude stocks rose by 5.4 million barrels in the last week, far more than analysts' expectations for an increase of 417,000 barrels, pointing to continued oversupply in the market.