All about oil (petroleum)

Petroleum, along with oil and coal, is classified as a fossil fuel. Fossil fuels are formed when sea plants and animals die, and the remains become buried under several thousand feet of silt, sand or mud. Fossil fuels take millions of years to form and therefore petroleum is also considered to be a non-renewable energy source.
Petroleum is formed by hydrocarbons (a hydrocarbon is a compound madeup of carbon and hydrogen) with the addition of certain other substances, primarily sulphur. Petroleum in its natural form when first collected is usually named crude oil, and can be clear, green or black and may be either thin like gasoline or thick like tar.
Oil was first discovered in the U.S. in 1859. At the beginning of the 20th century it supplied only 4% of the world’s energy; decadeslater it became the most important energy source.
Today oil supplies about 40% of the world’s energy and 96% of its transportation energy. Since the shift from coal to oil, the world has consumed over 875 billion barrels. Another 1,000 billion barrels of proved and probable reserves remain to be recovered. 

From now to 2020, world oil consumption will rise by about 60%. Transportation will bethe fastest growing oil-consuming sector. By 2025, the number of cars will increase to well over 1.25 billion from approximately 700 million today. Global consumption of gasoline could double. 

The two countries with the highest rate of growth in oil use are China and India, whose combined populations account for a third of humanity. In the next two decades, China's oil consumption is expected togrow at a rate of 7.5% per year and India’s 5.5%. (Compare to a 1% growth for the industrialized countries). It will be strategically imperative for these countries to secure their access to oil. 
Where are the reserves?
Proved oil reserves are those quantities of oil that geological information indicates can be with reasonable certainty recovered in the future from known reservoirs. Of thetrillion barrels currently estimated, 6% are in North America, 9% in Central and Latin America, 2% in Europe, 4% in Asia Pacific, 7% in Africa, 6% in the Former Soviet Union. Today, 66% of global oil reserves are in the hands of Middle Eastern regimes: Saudi Arabia (25%), Iraq (11%), Iran (8%), UAE (9%), Kuwait (9%), and Libya (2%). 
Petroleum, also called crude oil, is a thick, flammable,yellow-to-black colored liquid. Petroleum was first found oozing out of rocks on Earth's surface. Hence, its name comes from the Latin words petra, meaning rock, and oleum, meaning oil. Petroleum is a hydrocarbon, an organic compound containing only carbon and hydrogen. It is a mixture of other hydrocarbon compounds such as natural gas, gasoline, kerosene, asphalt, and, probably most important, fuel oil.Today, most scientists agree that oil was formed from the remains of plants and tiny animals that settled to the bottom of ancient oceans. These remains or sediments were buried by layers of mud and sand. Gradually, over millions of years, the weight of these accumulating layers built up great pressure and heat. The sediments packed together and became rock. The organic (once living) remains werechanged into kerogen, a waxy substance that forms oil and natural gas. Most of the world's petroleum is more than 100 million years old, and is thus called a fossil fuel.
Unlike coal, which stays in one spot unless moved by Earth's shifting crust, oil slowly migrates upward through cracks and pores, or tiny holes, in nearby rocks. Eventually the oil reaches a solid layer of rock and becomestrapped underneath in a reservoir (pool). Natural gas often occurs in association with oil. Most of the world's petroleum reservoirs lie deep underground in structures called anticlines—gently folded layers of rock that form an arch above the deposit. Petroleum can also be trapped by fractured layers (or faults), salt formations, and stratigraphic (rock) traps. Some oil is also contained in shales...