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Occurrence and Extraction of Petroleum:


              Petroleum  is  found  trapped  between  the  layers  of  impervious  rocks.  Petroleum  being

                lighter than water floats over it. Petroleum oil deposits are generally mixed with water, salt
                and earth particles. Natural gas is occurs above the petroleum oil.

              Petroleum is extracted by drilling holes also known as oil wells in the earth’s crust, where

                the presence of oil has been predicted by survey.
              The oil wells are drilled by using drillings rigs.

              The  petroleum  and  the  natural  gas  are  present  under  the  earth  surface  under  high
                pressure.

              So, when an oil well is drilled through rocks, natural gas comes out first with great pressure

                followed by the petroleum oil. After the gas pressure has subsided, petroleum is pumped
                out of the oil well.

              Earlier, drilling of oil wells for getting petroleum was done only on land, but later using new
                techniques now oil wells are now also drilled under the sea for extraction of petroleum oil.

              The  world’s  first  oil  well  was  drilled  in  Pennsylvania,  USA,  in  1859.  Eight  years  later  in
                1867oil was struck at Makum in Assam. In India, petroleum oil is found in Assam, Gujarat,

                and Mumbai High and in the river basins of Godavari and Krishna.














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