The importance of oil to global economies has been brought into focus as prices reach $100 a barrel.
Follow the links for a snapshot of the industry and how reserves, consumption and trade differ around the world.
The Middle East remains the biggest player in oil.
The region dwarfs the rest of the world, when it comes to reserves, ensuring its prominence on the global political stage. Saudi Arabia alone possesses 21.9% of the world's proved reserves.
The North Sea and Canada still have substantial reserves.
No-one knows how long the world's oil reserves will last, but even the oil industry suspects the world "peak" is now approaching.
It says it has 40 years of proven reserves at the moment - but it also said that 30 years ago.
In fact, the estimate has actually increased in recent years as production has fallen. Cutting consumption would prolong oil's life.
Demand is at an all-time high, fuelled by the continued economic expansion of the economies of China and India.
China overtook Japan as the world's second-largest consumer of oil in 2003 and is closing in on the US, with demand for oil growing at about 15% a year.
Western Europe and Japan are heavily dependent on oil imports as production cannot meet massive domestic demand.
The gas-guzzling US is the world's largest per-capita oil consumer but produces much of its requirements itself.
Producers in the Middle East, where oil costs so little, are also heavy users. Poorer countries consume much less per head.
The Middle East is the biggest oil producer, currently providing nearly one-third of the world's total.
Europe and Eurasia (mainly Russia and the UK) and North America are also big producers. The difference is, nearly all the Middle East oil is for export while Europe and the US do not produce enough to meet their own needs.
The weaker dollar has been driving up oil prices as investors have been using the commodity as an alternative to holding dollars.
Oil prices nearly doubled in value during 2007, but prices have still not reached a record high if inflation is taken into account.
Adjusting for inflation, US light crude's record peak of $101.70 came in 1980 against a backdrop of war between Iraq and Iran.