Oil prices dropped in the international market on Wednesday, stressed by rising U.S. inventories and the rift within OPEC intensified oversupply concerns. Brent futures slipped 3.6%, at $25.41 a barrel. U.S. West Texas Intermediate (WTI) crude futures dropped to $20.37 a barrel. Data released by the American Petroleum Institute showed a rise of 10.5 million barrels in U.S. crude inventories.