A U.S. appeals court on Friday said Exxon Mobil Corp and Royal Dutch Shell Plc affiliates may try to enforce part of a $1.8 billion arbitration award against Nigeria's state-run oil company, in a dispute concerning oil extraction near the African country's coastline.

In a 3-0 decision, the 2nd U.S. Circuit Court of Appeals in Manhattan said a lower court judge erred in rejecting the entire October 2011 award, which by 2018 had grown to $2.67 billion including interest, against Nigerian National Petroleum Corp.

It said the judge should have determined which parts of the award had been deemed enforceable by a Nigerian appeals court.

Lawyers for the companies did not immediately respond to requests for comment.

The dispute arose from a 1993 contract for Esso Exploration and Production Nigeria Ltd and Shell Nigeria Exploration and Production Co to invest billions of dollars to develop the Erha oil field on the Gulf of Guinea, and share profits with NNPC.

Extraction began in 2006. But disagreements soon arose, and Exxon and Shell said that by late 2007 NNPC was at the government's behest "lifting" more oil than the contract allowed, depriving them of billions of dollars.

Following the arbitration ruling, Exxon and Shell sought to enforce their award in Manhattan while NNPC sought to set it aside in Nigeria.

In Friday's decision, Circuit Judge Susan Carney said Exxon and Shell did not prove that setting aside part of the award violated public policy, and said U.S. courts should not second-guess Nigerian courts' substantive views on Nigerian law.

But she said the Nigerian judgments were "ambiguous" as to how much of the award was set aside, and more fact-finding was needed.

Friday's decision partially reversed a Sept. 2019 ruling by U.S. District Judge William Pauley in Manhattan.

Pauley died last July, and another judge will take over the case.

The case is Esso Exploration and Production Nigeria Ltd et al v Nigerian National Petroleum Corp, 2nd U.S. Circuit Court of Appeals, Nos. 19-3159, 19-3361.

Reuters