Oil prices surged about 4 percent on Thursday after U.S. inventory data showed a surprisingly large drawdown in crude stocks as imports into the U.S. Gulf Coast slid last week due to Tropical Storm Hermine.

U.S. crude stocks dropped 14.5 million barrels last week to 511.6 million barrels, the biggest weekly drop in stockpiles since January 1999, according to the U.S. Energy Information Administration. Analysts had expected a modest increase in inventories.