Oil is fueling the war chest for the group calling itself the Islamic State by more than $2 million per day, a study from consultant group IHS said.

A report from IHS Energy found IS, known also as the Islamic State in the Levant, is able to finance itself through a black market for oil.

"Oil fuels ISIL's war machine, notably including the military vehicles vital to its movements and fighting capabilities," analysis e-mailed Monday to UPI found. "Oil directly finances ISIL's myriad activities and encourages the activities of middlemen who sell, transport and export the oil and thus have a vested interest in ISIL."

IHS estimates the oil production controlled by IS is worth an estimated $800 million per year.

A U.S.-led air offensive against IS has targeted oil installations in Syria in an effort to cut off the group's source of revenue and fuel.

A recent report from the International Energy Agency found airstrikes were diminishing the terrorist group's ability to function and finance itself.

IHS estimates IS sells oil on the black market for an average $40 per barrel, roughly half the price on the global market.