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What is Petroleum? – Occurrence, Refining, Formation, Uses

Last Updated : 17 Jan, 2023
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Petroleum is a fossil fuel that is a very dark-coloured viscous liquid with a foul smell. It is commonly known as crude oil. Petroleum is always found between two rocks (non-porous). The word petroleum is derived from the Latin language “petra” means rock and ”oleum” means oil. That’s why, petroleum means rock oil. Petroleum or mineral oil is the next major energy source in India after coal. Petroleum refineries act as a “nodal industry” for synthetic textile, fertilizer and numerous chemical industries.

Where Petroleum Occurs?

Petroleum is found in fault traps between porous and non-porous rocks. Petroleum is found in 500 meters to 2000 meters depth. It is always found mixed with salt water, and being lighter than saltwater, Petroleum always floats over it.

Where Petroleum is Found?

  • Mumbai High, Gujarat and Assam are three major petroleum production areas in India. Ankleshwar is the most important field in Gujarat.
  • Assam is the oldest oil-producing state in India. Digboi, Naharkatiya and Moran-Hugrijan are the important oil fields in this state.
  • In Gujarat – Ankaleshwar, kalol, Mehsana, nawagam, kosamba and lunej.
  • Mumbai high which lies 160 km off Mumbai was discovered in 1973 and production was started in 1956.
  • In India, oil and natural gas are found in Krishna, Godavari and Kaveri basins on the eastern coast.

How Oil Wells are Managed to Extract Petroleum?

Firstly, the site location is mapped through geographical and geological methods by using seismology. And then with the help of giant rigs, a hole is drilled in the Earth’s crust. After reaching the rock cap, the natural gas comes out first with great pressure. Thus, after gas petroleum starts flowing out due to the pressure of natural gas. And the petrol is pumped out by using the electric motors.

Refining of Petroleum

Refining is a process of separating the various constituents and petroleum is a mixture of various constituents such as Petroleum gas, petrol, diesel, lubricating oil, paraffin wax etc. Refining petroleum is done by using the fractional distillation method.

Crude petroleum is a mixture of hydrocarbons of different states which can not be used in their raw form that’s why refining is done. At first, crude petroleum is heated to a temperature of 400°C or slightly above in the furnace. It occurs in sedimentary rocks. Oil extracted from the wells is crude oil which contains very impurities, it cannot be used directly and need to be refined. And the vapours of petroleum are fed into a tall column. Fractioning maintains itself at different temperatures. Due to this difference in temperature, the vapours with a higher boiling point condense first, but the vapours with a lower boiling point rise up and condense in different parts of the fractionating column. The gases which do not liquefy are taken out from the top of the fractionating column. Fractions of Petroleum are carried out in a petroleum refinery.

There are two types of refineries in India:

  1. Field based 
  2. Market based

Digboi is an example of field based refinery and Barauni is an example of market based refinery.

Formation of Petroleum

Diesel is obtained from Petroleum which is formed from animals living in the sea and when these organisms died their bodies get settled at the bottom of the sea which got covered with layers of sand and clay after some time. And high temperatures with high pressure along with the action of bacteria transformed these dead organisms into petroleum and natural gas.

Uses of Petroleum

  • From light automobiles such as motorcycles, and cars to heavy motor vehicles like trucks, and tractors everything runs on diesel and petrol.
  • It provides fuel for heat and lighting, lubricants for machinery and raw materials for a number of manufacturing industries.
  • It is an essential source of energy for all internal combustion engines in automation, railways and aircraft.
  • Its by-products are processed in petrochemical industries such as fertilizer, synthetic rubber, synthetic fibre, medicines, Vaseline, lubricates, wax, soap and cosmetics.

Some Important Fractions of Petroleum and their Uses


Boiling Point

Number of Carbon Atoms

Products Obtained/uses

Petroleum gas below 40 °C 1 – 4 LPG (Liquefied Petroleum Gas): fuel for home and industry
Gasoline and naphtha 40 – 160 °C 4 – 10 Petrol: motor fuel, aviation fuel, solvent for dry cleaning
Kerosene 150 – 250 °C 10 – 16 Kerosene: domestic fuel, jet engine fuel
Light Oil 250 – 350 °C 16 – 20 Diesel: fuel for motor vehicle
Heavy Oil 250 – 350 °C 20 – 25 Useful organic chemicals
Residue over 350 °C over 25 Lubricating oil and Paraffin wax

Sample Questions

Question 1: Where petroleum gas is used?


Petroleum gas is mostly used for household works specifically in the kitchens of restaurants and houses. As they use gas cylinders to run their stove which is filled up in the form of LPG.

Question 2: Write the full form of-

1. LPG
2. CNG


Full-form of LPG is Liquefied Petroleum Gas and of CNG is Compressed Natural Gas.

Question 3: For which type of vehicles do Petrol and diesel are suitable?


Petrol is suitable for small and lightweight vehicles like cars and scooters however, Diesel is suitable for heavy vehicles like trucks and buses.

Question 4: Where Paraffin wax is used?


Paraffin wax is used in making candles, cosmetics and electrical insulators and many more things.

Question 5: Which products are obtained from the Fractional Distillation of Petroleum?


Petrol, Kerosene, Diesel, Fuel oil, Paraffin wax, Lubricating oil, Bitumen are the products obtained from the various fractions of Petroleum.

Question 6: What are examples of fossil fuels?


Coal, Natural gas and Petroleum are some examples of fossil fuel.

Question 7: Which country is the leading producer of Petroleum?


United States is the top leading oil-producer of the World.

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