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 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.

Chevrons Venezuelan crude shipments have hit a roadblock as PDVSA, Venezuelas state oil company, revoked export authorizations for several tankers due to payment uncertainties linked to renewed U.S. sanctions.