I work in the Oilfield here in West Texas. There are fields out here that were thought to be depleted that are being re-entered and coming online anywhere from 20 to 100 bbls a day per well. As the technology advances so does the ability to get more and more oil out of the producing zones.
The technology being used in the middle east is anywhere from 10 to 30 years behind what we are using here in the U.S. Their oil is easy to get right now, years down the road it will be harder and they will have to advance their technology to some we haven't used in a while here.
This is just like buying a computer. You can go out today and buy the best computer money can buy. Then a few months later, it is no longer the best.