Until now, the surge in U.S. oil production from the Permian and other shale basins like the Bakken in North Dakota was absorbed at home, feeding refineries in the U.S. Gulf of Mexico coast. Now, U.S. refiners are finding it increasingly hard to process more of the kind of light crude pumped in the Permian as their plants were built to process denser heavy crude -- the type pumped in Venezuela and the Middle East.

"The United States is probably darn close to being able to process as much light crude as it can," Thomas J. Nimbley, the head of U.S. oil refiner PBF Energy Inc., told investors.

As a result, shale executives are traveling the world to seek new customers. Gary Heminger, the head of Marathon Petroleum Corp., for example, was recently in Singapore and South Korea looking for buyers for shale crude.

"All the incremental Permian production needs to be exported," said Raoul LeBlanc at consultant IHS Markit Ltd. and a former head of strategy at Anadarko Petroleum Corp. "The Permian needs to find refineries willing to take U.S. light sweet crude as a base-load, most likely in Asia."

Despite a tight oil market due to American sanctions on Venezuela and Iran mixed with OPEC production cuts, finding new buyers isn’t as easy as it sounds. The crude from the Permian is light, yielding lots of naphtha -- used in the petrochemical industry -- and gasoline, but comparatively little diesel. And most refineries want to produce diesel.

Until now, U.S. shale producers and oil traders had been selling most of their crude on spot transactions -- one at a time. As a result, American oil exports saw wildly different destinations from month to month, from Spain to Thailand to Brazil.

A few stable markets are starting to emerge. Oil refineries in Canada, Italy, the U.K., and South Korea are becoming regular buyers. And little by little, oil traders are securing long-term deals with overseas refineries, known as term contracts.

Yet, the rapid rise in oil exports is challenging. Not even Saudi Arabia in the 1960s and 1970s saw exports grow so quickly.

"The U.S. export market needs to transition from infancy to adulthood far more rapidly than any major exporter ever has," said Roger Diwan, another oil analyst at IHS Markit.

Key for U.S. oil exports is China, mired in a trade war with Washington. Until this year, Chinese refiners were buying large chunks of American shale exports. But the flows all but dried up in August. If U.S. oil exports are going to increase at the pace that executives and traders anticipate, the shale industry needs the White House to strike a trade deal with the Chinese.