US benchmark West Texas Intermediate (WTI) for delivery in September, which expires Thursday, dipped 32 cents to $40.48 after falling sharply in New York to its lowest level since March 2009.
Brent crude for October dropped 25 cents to $46.91 a barrel.
“US stockpiles unexpectedly expanded when the market was looking at a contraction, which heightened the global oversupply concerns,” said Bernard Aw, a market strategist at IG Markets in Singapore.
“This added pressure to crude prices, and we see WTI drop below $41, heading towards the key $40 level. We could see more downsides, given that the current conditions remain unfavorable to oil.”
The US Department of Energy on Wednesday said oil stockpiles rose 2.6 million barrels in the week ending August 14, and reported a 300,000 barrel rise at the closely watched Cushing, Oklahoma trading hub.
The surprise jump in inventories at a time when they normally fall added to concerns of a global surplus, particularly as signs emerge that demand is faltering in top energy importer China.
Analysts predict oil could now reach levels not seen since the throes of the financial crisis, pressured by a strong dollar and the anticipated return of Iranian oil to world markets.
But Daniel Ang, an investment analyst with Phillip Futures in Singapore, said he expects WTI to be supported at $40 a barrel in Thursday’s trading session.
“Technically, we are still seeing a very bearish momentum, however for prices to break below $40 is going to be an arduous task,” he said.
“We see $40 for WTI to be a strong psychological support. Thus, we would unlikely think that this would break during Asian hours (Thursday).”