Oil prices have trended lower on oversupply and weak demand since mid-June, when Brent hit a nine-month high of $115.71.
West Texas Intermediate for November delivery dropped $1.07 to $87.79 a barrel, after falling to $87.39 earlier in the session, its lowest since April 2013.
U.S. crude stocks climbed by 5.1 million barrels to 360 million in the week to Oct. 3, according to an inventory report on Tuesday from industry group the American Petroleum Institute (API). This was much larger than the build of 1.5 million barrels expected by analysts polled by Reuters.
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"The U.S. has a million barrels a day of oil due to the shale revolution, while there is softer growth in China. Japan is not firing on all cylinders," Le Brun said.
China's services sector weakened slightly in September as new business cooled, reflected in the services purchasing managers' index (PMI) compiled by HSBC/Markit and released on Wednesday. The marker pulled back to 53.5 in September from a 17-month high of 54.1 in August.
Oil prices could fall further by the weekend although this would depend on how the dollar performed.
"A little bit of profit taking in the U.S. dollar should support the commodities complex," Le Brun said.
The dollar index was at 85.841 in trade on Wednesday, off a four-year peak of 86.746 hit on Friday.
Brent could be around $90 a barrel by Friday, with U.S. oil trending towards $85 a barrel, Le Brun said.
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Geopolitical tensions could still provide some support to oil prices, but conflicts in the Middle East, North Africa and Ukraine have so far had only limited impact on crude output.
As fighting continued between Kurdish and Islamic State fighters for control of the Syrian Kurdish town of Kobani, the United States stepped up discussions with Turkey on Tuesday over its role in a U.S.-led coalition fighting the Islamist militants in Syria.
Libyan oil production has slipped below 900,000 barrels per day (bpd), down from as high as 925,000 bpd last month, due to a sit-in protest at Sirte Oil Co by local residents demanding jobs, a source at the National Oil Corporation said on Tuesday.