"...Oil fields contracted include the "super-giant" Majnoon Field, Halfaya Field, West Qurna Field and Rumaila Field." [1]
If you look up each of those fields, you'll see they are licensed to Shell, BP, and Exxon [2] [3] [4] [5]
Given all of those companies have a strong presence in the US and definitely have lobbying power. I'd say the US got effective control over one of the largest oil reserves in the world.
[1] http://en.wikipedia.org/wiki/Oil_reserves_in_Iraq
[2] http://en.wikipedia.org/wiki/Halfaya_Field
[3] http://en.wikipedia.org/wiki/West_Qurna_Field