Oil supplies
Crude oil is considered a limited resource. It is estimated that there is a total of 2,390 billion barrels (380 km³) of crude oil on Earth. Estimates of undiscovered reserves range from 275 to 1,469 billion barrels (44 to 234 km³). However, these numbers must be treated carefully as they include the amount of economically recoverable reserves, which can increase as new technologies are introduced.
About 77% of crude oil has already been discovered, and 30% of it has been used so far. Between 1859 and 1968, 200 billion barrels (31 km³) of oil were used, and since then oil production has stabilized to 22 billion barrels (3.5 km³) per year. In 2004, world consumption of crude oil is on track to surpass 82 million barrels per day, 30 billion barrels per year. It is estimated that oil reserves will become scarce by the 2050s. However, oil reserve numbers do not include sources such as tar sands and bitumen which are currently uneconomical, nor does it take into account possible coal derived production. Although these processes are not currently economical, they do vastly expand the amount of available hydrocarbons.
Most known reserves are concentrated in the Near East — around 41%. North America, Russia, and Antarctica are also rich in crude oil.
See also: List of oil fields, Petroleum
