Petroleum resources occur in most part of the world to some degree, however, the major commercially valuable resources occur in relatively few locations where geological conditions were appropriate for the formation and storage of these fuels underground. It is believed that petroleum (derived from Latin: petra=rock, oleum=oil) was formed from deposits of plant and animal remains since petroleum deposits are found almost exclusively in sedimentary rock formations laid down millions of years ago when plant life flourished.

Petroleum is a mixture of a number of hydrocarbons with some sulfur, nitrogen and organo-metallic compounds also present. A number of processing steps are involved in producing the various high value salable fuel streams such as gasoline, diesel and jet fuel from the petroleum.

Petroleum resources, both liquid and gaseous, have become the major sources of energy in many countries because of the availability and convenience of these fuels for both transportation engines and stationary power plants.

Oil Consumption and Reserves¹

The following table shows the oil consumption and the estimated reserves in 1996 in some countries (1 barrel of oil contains roughly 5.6 million Btu or 5.9 Giga Joule of energy):