Genel said the Kurdistan Regional Government exercised its right to take a stake in Miran production.
"Accordingly, Genel's working and paying interests in the Miran production sharing contract will fall from 100 percent to 75 percent, with the KRG's working and paying interests at 25 percent," the company said in a statement.
No financial terms were disclosed
The Miran contract area covers 293 square miles and contains gross resources estimated at 3.5 trillion cubic feet of natural gas and 95 million barrels of oil. Genel said it was working with the Kurdish government on a gas sales agreement for mid-2014.
The Kurdish and central Iraqi governments are at odds over who controls what aspects of the energy sector. The central government says unilateral deals with the KRG may violate the national constitution.
Genel in 2012 paid $156 million to take on Miran assets from Heritage Energy Middle East Ltd., a subsidiary of Heritage Oil.
The Miran field was discovered in 2009. Genel said an early production facility is already producing 2,000 barrels of oil per day.