Crude oil, an important fuel resource, is obtained from the sedimentary rocks of marine origin. It’s a naturally occurring petroleum product containing hydrocarbons and other organic compounds. But, all sedimentary rocks do not contain crude oil. Crude oil in India is found mainly in the sedimentary rocks of the tertiary period.
The process of the formation of crude oil began in the tertiary period. Marine life was abundant in various forms of flora and fauna during this period. Conditions were favourable for the oil formation. The living organisms, marine life, and vegetal matter got buried under the accumulated sediments of silt, sand, and mud. As time progressed, this undergoes chemical changes due to heat & pressure, resulting in the formation of crude oil and natural gas after millions of years.
In India, oil fields are of two types. On-shore oilfields and off-shore oilfields. The Major oilfields of India are as follows:
On-shore Oil fields in India
- The Brahmaputra Valley.
- Barmer area of Rajasthan.
- The Gujarat Coast.
1. Brahmaputra Valley
In India, Oil was first discovered in Assam (near Margherita) in the Brahmaputra valley in 1860 by Assam Railway and Trading Company. The oil-bearing strata extend from the Dehang Basin to the Surma valley. The main oil-producing wells are situated in the Dibrugarh and Sibsagar districts of upper Assam.
- The Digboi Oilfield: It is one of the oldest oilfields in India, situated in Tipam hills, Dibrugarh district. The first oil well in India ( even Asia) was drilled in Digboi. There are around 85 oil wells in this region. Oil from this region is supplied to the refinery at Digboi.
- The Naharkatiya Oilfield: In this region, oil production started in 1954. It lies about 32km to the southwest of Digboi on the left bank of the Burhi Dihing river. Oil from this area is supplied to the refineries of Noonamati (in Assam) and Barauni (in Bihar) through pipelines.
2. Gujarat Oil fields
Gujarat coast is the second-largest oil-producing region of the country. The important oilfields of this region are Ankleshwar, Khambhat-Luni, Ahmedabad-Kalol, Barkol, Katharina, and Sanand.
- Ankleshwar: It lies in the district of Bharuch. Oil from this field is rich in gasoline and kerosene. Oil is sent to the Trombay and Koyali petroleum refineries.
- Cambay-Luni Region: This oilfield is situated about 60km from the west of Vadodara. The oil found here is very light. The estimated reserves of crude oil from this region are over 30 million tonnes.
- The Ahmadabad-Kalol Region: It lies to the north of the Gulf of Khambat and is spread up to Mehsana. Kalol is an important oil field in this region. Oil is sent mainly to the refinery at Koyali.
3. Rajasthan Oil fields
Rajasthan is one of the largest on-shore oil-producing states in India. The Mangala area in Rajasthan is the largest inland oil discovery in India. The major oil fields in this area are Mangala, Saraswati, and Rajeshwari oilfields.
In addition to these oilfields, crude oil has been discovered in the Bilaspur Tehsil of Rampur district in Uttar Pradesh, Jawalamukhi area of Punjab, and Barmer district of Rajasthan.
Off-shore Oil fields in India
- Western Coast Oilfields.
- Eastern Coast Oilfields.
1. Western Coast off-shore Oil fields
In the offshore region, the major oil-producing fields of the western coast are as follow:
- Bombay High Oilfields: It is the largest petroleum-producing oilfield in India, contributing over 65% to the total crude oil production. The estimated reserves from this area are about 35 million tonnes of crude oil and about 40,000 million cubic meters of natural gas. Oil production from this Mumbai High oilfield started in 1976.
- Bassein Oilfield: It is located to the south of Bombay high. Here rich deposits of oil and natural gas have been found at a depth of over 1900m.
- Aliabet Oilfield: It is situated at Aliabet island, about 45km to the south of Bhavnagar.
2. Eastern Coast Oil fields
Crude oil and natural gas have been discovered in the basin and delta regions of the Mahanadi, Godavari, Krishna, and Cauvery rivers.
- The Rawa field in the Godavari-Krishna off-shore basin is an important oilfield expected to produce about 3 million tonnes of crude oil annually.
- The Narimanam and Kovilappal oilfields of the Kaveri delta are also major on-shore oilfields.
In addition to these, there are strong possibilities of oil deposits to be found on the off-shore of the Andaman and Nicobar, Gulf of Mannar, Baleshwar coast, and in Punjab, Haryana, Uttar Pradesh.
Frequently Asked Questions
Which is the Largest Oilfield in India?
Mumbai High field is the largest oilfield in India, situated about 161km north of the Bombay coast in Mumbai, Maharashtra.
Which state is the largest producer of oil in India?
Rajasthan is the largest producer of crude oil in India, followed by Gujarat and Assam.
Which is the oldest oilfield in India?
Digboi oilfield in Assam is the oldest oilfield in India, where oil was discovered in the early 18th century.