An analysis of field-by-field data shows Iraqi production is significantly higher than official estimates used by OPEC.
One refinery was fixed after IS was cleared out. The other is part of a political deal between Baghdad and Kurdistan.
Investigators suspect members of the Badr Organization paramilitary group conducted a small but steady smuggling operation at a makeshift military base south of Kirkuk.
In territory that was ostensibly liberated two years ago, security forces, civilians, and energy infrastructure have become regular targets of an intensifying IS guerrilla war.