U.S. oil closed down slightly on Wednesday as concerns of a growing global supply glut offset optimism in recent weeks about declining U.S. production.
Crude futures have lost about 6 percent so far this week, sliding after OPEC reportedly pumped 110,000 barrels per day more in September than in August, and nearly 2 million bpd above forecast demand for 2015.
In comparison, U.S. shale oil production is expected to fall by 93,000 bpd in November, although it would be the largest monthly cut since the U.S. Energy Information Administration (EIA) began compiling shale output data in 2007.
More immediately, U.S. crude stockpiles likely rose by almost 3 million barrels last week, analysts polled by Reuters forecast, as refinery runs declined from autumn maintenance works. The American Petroleum Institute will issue preliminary stockpiles data at 4:30 p.m. (1730 GMT) on Tuesday ahead of official inventory numbers from the EIA on Wednesday.