Crude oil gets formed at the bottom of the sea from the remains of dead plants and animals. The remains were covered by mud on the sea bed. The mud turns rock gradually. Under the rocks, the dead living things are under very high pressure. Rocks around them also added up some heat. Thus in the absence of air, high pressure and heat, the dead remains got converted into oil. This oil is the crude oil. It is also sometimes called ‘raw petroleum’.
Crude oil takes millions of years to form. Hence it is a fossil fuel which exists in natural underground reservoirs. Petroleum is obtained by processing crude oil at petroleum refineries. It is in its liquid form during extraction from its source. Geologists or the rock scientists can find out which place could be drilled to obtain crude oil. ‘Fractional distillation’ is one such process which is used by them to extract oil from under the rock.
There are many oil producing regions around the world. Leading countries include Russia, Saudi Arabia and the United States. Oil is classified based on the location from which it is extracted. Crude oil is actually a mixture of hydrocarbons including paraffins, naphthalene, aromatics and asphaltics. The density of the oil depends on the length of hydrocarbons it contains.
Asphaltics are about 6% in most crude. They are very much undesirable component but their ‘stickiness’ makes them excellent for use in road construction. Aromatics which constitute 3 – 30% are also undesirable as burning those results in soot. Napthenes make up 30 – 60% of crude and are more viscous. The most desired content in crude are the paraffins which make up 15 – 60% of crude and are used to make fuels.