Oil prices are sliding under a surge in supplies and signs of slowing in the global economy. West Texas Intermediate crude dropped 93 cents a barrel on Thursday, to 45.61.
International benchmark Brent crude fell 60 cents, to 54.31 a barrel. Production is up in Russia, Iraq, and the U.S., which is now the world's top oil producer.
Demand is expected to drop as the slowdown in China's economy and turmoil in stock and currency markets makes investors nervous.