Nigeria’s oil, displaced by U.S. shale, has found an unlikely new outlet this year: the coast of the continental United States that is farthest from the African country’s shores.

The shale boom has upended the global market, turning the United States from a keen buyer of Nigerian oil to an aggressive competitor.

But no pipelines easily connect the shale hub at the Permian basin, located in Texas and New Mexico, to the West Coast, driving the latter to look to Nigeria to quench its thirst for crude.

Early this year, Californian refineries began loading up on Nigerian oil – taking cargoes of Qua Iboe, Bonga, Erha, Forcados and others, according to traders and Refinitiv Eikon data.

The more than 6 million barrels that the U.S. West Coast imported from Nigeria between April and August this year was almost four times higher than the amount for all of 2018.

The route is relatively rare for cargoes that must weather the 20,000-km (12,500-mile), 40-day journey from Nigeria’s lush coasts, around South America’s Tierra del Fuego and up to Los Angeles.

Traders said a combination of market factors – including the difficulty and expense of getting U.S. crude oil to the West Coast – made Nigerian grades attractive.

“It makes more cost sense. Even if U.S. crude is closer on the map, when you factor in the price and availability of taking in barrels from Louisiana or Nigeria, Nigeria came out cheaper,” one seller of West African oil said.

The purchases are a rare glimmer of hope this year for Nigerian oil, which now competes with U.S. shale for buyers, including in its top outlet, India.

The United States had historically been a heavy importer of crude oil, but shale production, coupled with the lifting of a four-decade export ban, transformed it into a net exporter of oil and fuels by late last year.

Barrels from this U.S. oil bonanza sailing to domestic shores face added costs, however, due to a century-old law called the Jones Act, which mandates that only U.S.-flagged vessels can transport it.

The restriction often makes freight within the United States more costly than much longer journeys.

But traders warn the surprise opening of the West Africa-West Coast export window, or arb, could be short-lived due to the timescales and distance involved.

“The arb may be already shutting. The price factors which made a cargo exporting today look like a good deal would have been happening over a month ago when the deal was made,” a major buyer of West African oil said.

“They won’t be the same today and certainly won’t be the same over a month from now when the cargo arrives.”

The need to refine oil into low-sulphur shipping fuels in time for stricter environmental rules on Jan. 1 may also have lured those cargoes, as West Africa is home to the kinds of crude most suited to such products. This boon could be fleeting too.

“The honeymoon will be over in a year from now,” said Ehsan Ul-Haq, lead analyst with Refinitiv.

“At present, all refiners are desperate to produce marine gasoil or very low-sulphur fuel oil. Once the market reaches equilibrium … there will be less interest.”

REUTERS