Oil prices fell more than 1 percent on Wednesday after OPEC reported its September oil output at eight-year highs, offsetting optimism over the group's pledge to bring a global crude glut under control.
The dollar index's climb to a seven-month peak also weakened demand for greenback-denominated crude among holders of euro and other currencies, traders said.
Adding weight to the market was the possibility that the American Petroleum Institute could report the first build in U.S. crude stocks in six weeks in preliminary inventory numbers due at 4:30 p.m. EDT (2030 GMT), traders said. Analysts expect the U.S. government to say on Wednesday that crude stockpiles rose 300,000 barrels last week.
Brent crude futures were down 56 cents, or 1.1 percent, at $51.85 a barrel at 2:38 p.m. (1838 GMT). U.S. West Texas Intermediate (WTI) crude futures settled down 61 cents, or 1.2 percent, to $50.18 per barrel.