Question

how is petroleum ontained? (more than 100 words)

Answer 1

Over a period of millions of years, the remains of dead plants and animals, in the absense of air, got converted into petroleum under the combined effect if high temperature, high pressure and bacteria. The petroleum so formed passed through porous rocks until it got trapped between some impervious rocks. Petroleum is obtained by drilling holes (oil wells) into the earth's crust where the presence of oil has been predicted by a survey. When a well is drilled through the rocks, natural gas comes out first with great pressure and after some time the oil comes out by itself due to gas pressure. After the pressure has subsided, the crude oil is pumped out of the oil well. The first oil well was drilled in pennsylvania (USA) in 1859. Oil was discovered in India in 1867, at Makum in Assam.

(126 words)