Crude prices tumbled to 2½-month lows on Thursday after the U.S. government reported a stockpile build four times above market expectations.
Also weighing on markets was an OPEC forecast that said maintaining the producer group's current pumping rates would boost supplies by half a million barrels of crude daily by next year.
Crude futures were down about 3 percent each after U.S. oil inventories rose for a seventh straight week. Stockpiles increased by 4.2 million barrels last week, compared with expectations for a million-barrel build in a Reuters poll.
"It's another data point highlighting the oil glut in the U.S. or the global markets for that matter," said Chris Jarvis, analyst at Caprock Risk Management in Frederick, Maryland.