I am fairly sure that it would be cheaper to just buy oil and let the countries shipping it worry about the security. I suspect a lot of mucking about that the US does in the middle east is because the powers that be in the US think that using the American military to support American oil interests is a good and reasonable thing to do. Of course, that was a major driver for Cheney but I'm not convinced it isn't a big driver for a whole lot of politicians be it Republican or Democrat. Especially when the oil companies funnel boat loads of cash their way to use the American military to protect their oil shipments.