Formation of Petroleum and Mineral Oil, Distribution of Petroleum and Mineral Oil in India, On-shore and Off-Shore Oil Production in India.
Petroleum and Mineral Oil
- Petra == rock; Oleum == oil.
- Petroleum or Mineral oil is obtained from sedimentary rocks of the earth.
- Petroleum fuels on burning gives little smoke and leaves no ash. So they are better than coal.
Constituents of Petroleum and Mineral Oil
- 90 to 95 per cent Hydrocarbons.
- 5 – 10% organic compounds containing oxygen, nitrogen, sulphur and traces of organometallic compounds.
Formation of Petroleum and Mineral Oil

- All sedimentary rocks do not contain oil.
- An oil reservoir must have three prerequisite conditions.
- Porosity [tiny gaps in soil] so as to accommodate sufficiently large amounts of oil;
- permeability [allowing liquids or gases to pass through it.] to discharge oil and/or gas when well has been drilled;
- the porous sandstone beds or fissured limestone containing oil should be capped below by impervious beds [not allowing fluid to pass through].

- Most of the oil gets collected in the anticlines or fault traps.
- Oil on a commercial scale is usually found in crests of anticlines [where the sedimentary rock strata are inclined and folded].
Distribution of Petroleum and Mineral Oil in India
- Process began in tertiary period [3 million years ago].
- Most of the oil reserves in India are associated with anticlines and fault traps in the sedimentary rock formations of tertiary times.
- In tertiary period, aquatic life was abundant in various forms, especially the minor microscopic forms of flora and fauna.
- Conditions for oil formation were favourable especially in the lower and middle Tertiary period.
- Dense forests and sea organisms flourished in the gulfs, estuaries, deltas and the land surrounding them during this period.

Extent of Oil Bearing Strata in India
- 1 lakh sq km or 42 per cent of India covered with sedimentary rocks.
- 10 lakh sq km form marine basins of Mesozoic and Tertiary times.
- Total continental shelf of probable oil bearing rocks amounts to 2 lakh sq km.
- The total sedimentary area including both on shore and offshore comprises 27 basins.
- Mumbai High, the Khambhat Gulf and the Assam are the most productive areas.

On-shore Oil Production In India
- Brahmaputra valley of north-east India.
- Barmer area of Rajasthan.
- Gujarat coast in western India.
- Cauvery on-shore basin in Tamil Nadu.
- Andhra Pradesh has both on-shore and offshore oil reserves.
Assam Oilfields
- Oldest oil producing state in India
- The main oil bearing strata extend for a distance of 320 km in upper Assam along the Brahmaputra valley.
- Oilfields of Assam are relatively inaccessible and are distantly located from the main consuming areas.
- Oil from Assam is therefore, refined mostly in the refineries located at Digboi, Guwahati, Bongaigaon, Barauni and
The Digboi field
|
Tipam hills, Dibrugarh district |
Oldest oil field of India |
The Naharkatiya field
|
Left bank of Burhi Dihing river |
32 km southwest of Digboi
Oil from this area is sent to oil refineries at Noonamati in Assam (443 km) and Barauni in Bihar (724 km) through pipeline. |
The Moran-Hugrijan field
|
40 km south-west of Naharkatiya |
|
Gujarat Oilfields
- Ankleshwar, Khambhat or Lunej, Ahmedabad and Kalol, Nawgam, Kosamba, Kathana, Barkol, Mahesana and Sanand are important oilfields of this region.
- Ankleshwar: Oil from this field is sent to refineries at Trombay and Koyali.
Rajasthan Oilfields
- One of the largest inland oil discoveries was made in Banner district of Rajasthan.
- Other important discoveries == Mangala oil field, Sarswati and Rajeshwari.
- Rajasthan is the largest on shore oil producing state of India.
Off-Shore Production in India
Western Coast
- Mumbai High, Bassein and Aliabet.
- Mumbai High: 1974; rock strata of Miocene age.
- Sagar Samrat, Bassein: south of Mumbai High.
- Aliabet: Aliabet island in the Gulf of Khambhat.
Eastern Coast
- The basin and delta regions of the Godawari, the Krishna and the Cauvery rivers hold great potential for oil and gas production.
- The Rawa field in Krishna-Godawari off-shore basin is an important one.
- The Narimanam and Kovilappal oilfields in the Cauvery on-shore basin are also important.
Petroleum Refining
- India’s first oil refinery started working way back in 1901 at Digboi in Assam.
- 1954: another refinery at Tarapur (Mumbai).
- Refinery hub and refining capacity exceeds the demand. Excess refined oil and other petroleum products are exported.
- Oil from wells is transported to nearest refineries through pipelines.
Advantages of Pipeline
- Ideal to transport liquids and gases.
- Pipelines can be laid through difficult terrains as well as under water.
-
- It needs very little maintenance.
- Pipelines are safe, accident-free and environmental friendly.
Disadvantages of Pipelines
- It is not flexible, i.e., it can be used only for a few fixed points.
- Its capacity cannot be increased once it is laid.
- It is difficult to make security arrangements for pipelines.
- Detection of leakage and repair is also difficult.
Crude Oil Pipelines
- Salaya-Mathura Pipeline (SMPL)
- Paradip-Haldia-Barauni Pipeline (PHBPL)
- Mundra-Panipat Pipeline (MPPL)
Petroleum Product Pipelines
Remember locations of Oil Refineries and Major Oil producing centers. Pipeline are the ones that connect these centers.
- Guwahati-Siliguri Pipeline (GSPL)
- Koyali-Ahmedabad Pipeline (KAPL)
- Barauni-Kanpur Pipeline (BKPL)
- Panipat-Delhi Pipeline (PDPL)
- Panipat-Rewari Pipeline (PRPL)
- Chennai – Trichy – Madurai Product Pipeline (CTMPL)
- Chennai-Bangalore Pipeline
- Naharkatia-Nunmati-Barauni Pipeline == first pipeline constructed in India
- Mumbai High-Mumbai-Ankleshwar-Koyali Pipeline.
- Hajira-Bijapur-Jagdishpur (HBJ) Gas Pipeline == world’s largest underground pipeline
- Jamnagar-Loni LPG Pipeline == longest LPG pipeline in the world
- Kochi-Mangalore-Bangalore pipeline
- Vishakhapatnam Secunderabad pipeline
- Mangalore-Chennai pipeline
- Vijayawada-Vishakhapatnam pipeline

Share of Oil in India’s Power Generation

India’s Oil Imports

Primary References: NCERT Geography, Encyclopedia Britannica, Indian Geography by Kullar [Amazon and Flipkart]
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Barmer district wrongly typed as Banner. Kindly fix that.
Also add a small note on what on-shore and off-shore means.
Hey thanks..for correction ‘banner district’ I was reading it for the first time
Thanku pmfias you are making a great contribution. Your content is well researched and of good quality very helpful for many of us UPSC aspirant.:)
manali refinery is in chennai not H.P.
The places have been mentioned and not the name of the refinery, there’s a refinery in Manali and yes Northern chennai the name of the refinery is Manali refinery! 🙂