Second, reserves are based on the amount of oil that is present and financially viable to extract.

FORBES: Playing The Treasury's Numbers Game

Iraq is home to the second largest reserves of oil in the world, after Saudi Arabia, but it is likely to take many years to bring oil from untapped areas to market.

BBC: Iraqi oil deals up for grabs

It has the second-biggest reserves after Saudi Arabia in terms of liquid oil reserves, and it has relatively simple geology.

CNN: Oil will shape Iraq's future