James Joiner, over at OTB, has published a map where the area of the country is proportionate to its share of known oil reserves.
I have a few points to add. First, these are known reserves. Two weeks ago Brazil announced finding oil fields to rival (or surpass) Venezuela. One part of the contest between Russia and Canada over the north pole is the prospect for as-yet undiscovered oil. Second, available oil is always at a given price. Change the price and you change the amount it can be profitable to produce. Third, I don't trust the estimates from the governments of Saudi Arabia and Iran. Influence in OPEC--and one's portion of the oil to be released-- is directly related to national estimates of reserves. Every country--and probably Saudi Arabia tops the list--has reasons to overestimate what they have.
Nevertheless, it's a sobering reminder of why the middle east looms so large in American (and everyone else's) strategic calculations.