It has always been an axiom of world energy markets that Persian Gulf oil is both easy and cheap to produce. The crude that gushes from the scorching desert sands of Saudi Arabia, for example, is widely thought to cost less than $5 a barrel to produce, compared to the $70 price tag on raising a barrel from deep Atlantic waters. But, many of the Persian Gulf oilfields have been producing for decades, and an increasing number of the newer fields in the region contain heavier and harder to extract crudes. Squeezing out the remaining reserves from some existing fields and developing new more complicated ones will be costlier and will require more advanced technology. As a result, more Gulf countries are exploring the use of enhanced oil recovery (EOR)