DEFINITION of 'Oil Field'
A tract of land used for extracting petroleum, or crude oil, from the ground. Although the exact origin of oil is still contested, most consider petroleum a "fossil" fuel, created from dead organic material often found in ancient seabeds thousands of meters below the surface of the earth. There are more than 40,000 oil fields around the world, many of the largest of which are found in the Middle East.
BREAKING DOWN 'Oil Field'
While tens of thousands of oil fields have been discovered, less than than 10% of them have had a significant impact on worldwide crude oil supply. Ghawar Field in Saudi Arabia, which started production in 1951, is by far the largest oil field uncovered so far, having yielded about 60 billion barrels of "black gold" through 2005.