Oil prices fell on Wednesday after an unexpected rise in U.S. crude stocks, adding to a picture of global oversupply that has dragged down values over the past year. Industry data released on Tuesday by the American Petroleum Institute (API) showed crude inventories at the Cushing, Oklahoma hub rose 2.3 million barrels last week, compared with analyst expectations for a decrease of the same volume. “The U.S. crude oil stocks build reported by the API last night is weighing on prices,” said Tamas Varga, analyst at London brokerage PVM Oil Associates.