A vessel chartered by Chevron carrying some 500,000 barrels of Venezuelan oil is about to complete the discharge of the cargo at a Venezuelan port, according to shipping data and a source, following state company PDVSA's order to return the crude amid payment uncertainty related to U.

Chevron Corporation, a major U.S.-based oil company, has been told to send back almost 1 million barrels of oil to Venezuela. This unexpected order comes just as Chevron was trying to secure as much oil as possible before shutting down its operations in the country.

Chevron Corp. was ordered to return nearly 1 million barrels of Venezuelan oil to Petroleos de Venezuela SA in a blow to the oil major, which was working to secure crude before wrapping up operations in the country when a US sanctions deadline hits in May.