US benchmark West Texas Intermediate (WTI) for delivery in November delivery dropped 63 cents to $46.01 a barrel from Wednesday´s close.
Brent North Sea crude for November delivery fell 18 cents to stand at $48.97 a barrel in London afternoon deals.
The US Department of Energy will publish inventory data against a backdrop of market concern about a supply glut owing in part to weaker demand from China, the world´s biggest energy consumer.
Prices had fallen Wednesday, as weak Chinese trade data and poor consumer spending numbers in the US added to a picture of a slowing global economy.
Underpinning the bearish sentiment has been a forecast this week from the International Energy Agency that pointed to much slower oil demand growth next year.
US crude inventories are meanwhile expected to have risen last week.
A Bloomberg News survey showed stockpiles are expected to have increased by 2.58 million barrels in the week to October 9.