There are several huge oil fields famous throughout the world. The Ghawar field in Saudi Arabia, discovered in 1948, is considered the biggest and the best known, producing about 5 million barrels per day, with estimated reserves exceeding 70 billion barrels. And this is above the 70 billion or so already extracted. Ghawar is why Saudi Arabia leads OPEC. But the Permian Basin, a 300-mile expanse from west Texas to southeastern New Mexico, is headed to becoming the biggest in the world.