Crude oil is a mixture of hydrocarbons that exists in a liquid phase in natural underground reservoirs. Crude oil is the most important energy carrier at a global scale and since all kinds of transport rely heavily on oil, the future availability of crude oil is of paramount interest. Crude oil is classified by the location of its origin (e.g. West Texas Intermediate, WT or Brent) and often by its relative weight or viscosity (light, intermediate or heavy).

Saudi Arabia, Russia and United States are the top three crude oil producing countries in the world. OPEC countries account for more than three quarters of oil reserves in the world. OPEC has great influence on the world crude oil market. Saudi Arabia is also the major exporter of crude oil followed by Russia, Iran, UAE and Nigeria. Among major consumers of crude oil, the US tops the list followed by China, Japan, USSR and India.

India reserves second highest crude oil deposits in Asia-Pacific after China. It is the sixth largest consumer of crude oil in the world with about 70% of its local requirement met through imports. The country consumed average of about 2.7 million barrels per day during 2006 and 2008. The country currently stands at third largest importer of crude oil in the world. Currently, state-owned Oil and Natural Gas Corporation Ltd is the biggest producer of crude oil (largely from the Mumbai High offshore fields).