Yet, in a trade that illustrates how the rise of the American shale industry is upending energy markets across the globe, the U.A.E. bought oil directly from the U.S. in December, according to data from the federal government. A tanker sailed from Houston and arrived in the Persian Gulf last month.

The cargo of American condensate, a type of very light crude oil, was preferred to regional grades because its superior quality made more suitable for the U.A.E's processing plants, a person with knowledge of the matter said, asking not to be identified discussing a commercially sensitive matter.

"As a member of OPEC and a large crude producer, I would imagine they would be very self-sufficient in their own crude supply," said Andy Lipow, president of Lipow Oil Associates LLC. The purchases of U.S. oil aren't likely to continue, given the U.A.E.'s own supply, Lipow said.