Marathon said it made the discovery while working in the Harir block, located 40 miles northeast of Erbil, administrative center for the semiautonomous regional Kurdish government.
The company, which has headquarters in Texas, said its initial testing yielded more than 11,000 barrels per day of "high quality oil" and approximately 72 million cubic feet per day of non-associated natural gas.
Lee Tillman, chief executive officer for Marathon Oil, said in a statement the Kurdish north of Iraq has proved itself a major regional producer.
"As the first large U.S. publicly traded company to enter in October 2010, Marathon Oil is pleased to have a strong presence in the Kurdistan Region of Iraq," he said Wednesday.
The semiautonomous Kurdish government is at odds with the federal government over who controls what aspects of the energy sector. Oil from the Kurdish north typically flows north to Turkish export terminals.
Marathon holds a controlling 45 percent interest alongside French energy company Total, with a 35 percent interest, and the Kurdish government, with a 20 percent stake.
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