With estimated reserves of 9 billion barrels, the giant Kirkuk oil field could produce more than a fifth of Iraq's current output.
But not, it's reported, with help from BP.
Sources tell Reuters it has pulled out of a $100 million exploration contract, after that expired with no agreement on the field's expansion.
Iraq and BP first started collaborating on Kirkuk in 2013 and in May 2018 signed agreements to triple output there.
The oilfield had been restored to Baghdad's control the year before, after Iraqi government forces dislodged Kurdish fighters from the area.
The BP decision comes as Western energy companies reassess their operations in the region.
After months of anti-government protests, video Reuters filmed on Tuesday (January 21) shows Iraqi security forces dispersing demonstrators in the southern city of Basra.
And, any potential conflict between the U.S. and Iran could see Iraq on the frontline.
The reports say BP informed local authorities last month it was pulling staff out of the oilfield.
A decision taken, it's said, after some, quote, "not encouraging" results of a field study it carried out.