Petroleum is one of the most important substances. Petroleum is a naturally occurring liquid. Petrol, diesel, jet fuel, lubricating oil, wax and many other products are manufactured by refining petroleum.
The word ‘petroleum’ comes from the Latin ‘petra’ which means ‘rock’ and ‘oleum’ which means ‘oil’. So the word actually means ‘rock oil’.
Petroleum is mainly a compound of carbon and hydrogen with presence of some other substances in minute quantities, mainly sulphur. It is the remains of animals and plants lived millions of years ago. Long back, major portion of earth was covered by water. Marine plants and animals stored energy from sun in their bodies. As they died, they sank to the bottom of seas and oceans and got covered by tiny particles of rock and soils. Because of the functions of v bacteria and chemicals, over long periods of time, tiny oil drops were formed.
Inside of the earth has different layers including porous rocks. The droplets seeped into these porous and got stored. As the oil droplets concentrated they started moving breaking the porous, but were blocked again by non porous rocks. These rocks lie deep underground. These areas became storage places of petroleum.
Again over a period of time, crust of the Earth shifted a lot. These shifting pushed the bed of the ocean down in some places and raised it in other areas. The raised portion became mountains and continents. The oil bearing rocks at the bottom of the ocean were pushed this way and that shifting to different places, away from the shore. And that is why we find oil in desert. This crude or petroleum is reached by drilling beneath the Earth’s surface.