PETROLEUM OR CRUDE OIL

PETROLEUM OR CRUDE OIL The word 'petroleum' has been derived from the word 'petra', which means rock, and 'oleum' which means oil. Thus 'petroleum' means 'rock-oil'. It is one of the important mineral fuels and is a complex mixture of hydrocarbtm compounds with minor amounts of ir.\1purities like nitrogen, sulphur and oxygen. The liquid pet.roleum is called crude oil, petroleum gas is called natural gas and the semi-solid to solid forms of petroleum are known as asphalt, tar, pitch, bitumen, etc.

For petroleum to accumulate in commercial quantities in an area, the"oil mttSt originate in a source bed. A marine shale, once a black mud rich in organic compound, is thought to be a common source rock. The oil then migrates to permeable reservoir rocks after travelling for long distances both vertically and horizontally. The source beds tend to lack the permeability necessary for profitable extraction of the oil. A non-permeable layer must occur above the reservoir bed. A favourable structure must exist.

Three principal grades of crude oil are considered important. Paraffin-Base Oil with a high percentage of the lighter hydrocarbons such as methane gives products, such as petrol, paraffin and high r;rade lubricating oils which are commercially more valued. Asphalt-Base Oil consists mainly of the heavier hydrocarbons with a viscous, asphaltic base. Mixed-Based Oil is an intermediate group with mixed properties of the lighter and heavier oils. It has use in lubricants and fuel oils.

Economic Uses The chief use of petroleum is as fuel, particularly in transport operations. The petrochemical derivations of petroleum have a wide range of uses in agricultural, industrial and medicinal industries. It is also used for the purpose of generation of heat and power.