Oil prices tumbled nearly 3 percent on Wednesday after a record weekly build in U.S. crude stocks added to worries of all-time highs in OPEC production that suggested little could be done to rein in a global glut.
Prices were little changed after the U.S. Federal Reserve said it would leave its interest rate policy unchanged.
The U.S. government's Energy Information Administration (EIA) said crude inventories rose by 14.4 million barrels for the week ended Oct. 28, versus analysts' expectations for a build of 1 million barrels. It was the biggest ever rise in U.S. crude stocks in a week, overwriting a 2012 record.
"This is very, very, very bearish. Nothing else in the report matters," said James L. Williams, energy economist at WTRG Economics in London, Arkansas.
The stunning build came as refineries cut output and U.S. crude imports rose last week by 1.99 million barrels per day. U.S. oil production also rose slightly to 8.522 million barrels a day.