The whole point of the invasion was control of oil. It wasn't just profit, nor was it access, since Iraq, like any other country, would sell to anyone willing to pay. The point was to get American bases, permanently, in the heart of the world's oil producing region.
They don't plan to leave. If they ever do, after leaving some sort of quisling government behind, they'll do a Vietnam on the country, meaning they'll destroy it so badly so as to send a message to anyone else, such as Iran, who might consider standing up to them.
By my count, I'm the third Canadian on this thread. I sure hope we don't get invaded, Vroom