The U.S. Energy Department's Energy Information Administration reports there was a "sharp decline" in the amount of crude oil imported from Nigeria since January when compared to last year, preliminary weekly data indicate.
In January, the United States imported 449,000 barrels of Nigerian crude oil per day, a 54 percent decrease from the same time last year. That marks the largest monthly decline since 2002.
The EIA said about 30 percent of the overall decline was due to the idling of the Trainer refinery and the Marcus Hook refinery, both near Philadelphia.
The agency said declines were attributed to the quality of Nigeria crude and because using domestic crude oil like West Texas Intermediate, Bakken and Eagle Ford was cheaper.
"Given the growing production from the Bakken and Eagle Ford formations and associated transportation constraints, these inland crudes have been selling at a discount to waterborne crudes on the Gulf Coast, providing refiners in that area further incentive to switch from imported crude to inland, domestically produced crude when available," the agency said in a statement.