Investing.com - Oil prices reversed earlier gains to trade lower on Thursday, as lingering concerns over a glut in world markets drove down prices.
Crude oil for delivery in December on the New York Mercantile Exchange shed 51 cents, or 1.25%, to trade at $40.24 a barrel during U.S. morning hours. It earlier fell to $39.89, the lowest since August 27.
Meanwhile, the more actively traded January contract slumped 26 cents, or 0.62%, to $41.69.
The U.S. Energy Information Administration said Wednesday that crude oil supplies rose by 252,000 barrels last week, disappointing market players who had hoped for a modest decline.
Supplies at Cushing, Oklahoma, the key delivery point for Nymex crude, increased by 1.5 million barrels, the EIA reported, above forecasts for a build of 0.8 million barrels.
Total U.S. crude oil inventories stood at 487.3 million barrels as of last week, remaining near levels not seen for this time of year in at least the last 80 years, underlining concerns over a domestic supply glut.
Elsewhere, on the ICE Futures Exchange in London, Brent oil for January delivery inched down 2 cents, or 0.03%, to trade at $44.12 a barrel.
The oil market has been on the defensive in recent months amid uncertainty about how quickly the global glut of crude is set to shrink.
Global oil production is outpacing demand following a boom in U.S. shale oil production and after a decision by the Organization of Petroleum Exporting Countries last year not to cut production.
OPEC will meet on December 4 to decide whether to extend their strategy of defending market share by keeping production high.