Minerals of Assam: Oil, Gas, Coal and Limestone
Assam is not usually described as a mineral state, yet it holds a place in the industrial history of India that no other region can match. Asia's first oil well was drilled here, India's first refinery was built here, and the state still supplies a large share of the country's crude oil and natural gas. Alongside petroleum, Assam has workable deposits of coal and limestone, and these four minerals together - oil, gas, coal and limestone - explain why refineries, fertiliser plants, cement works and petrochemical units cluster in the Brahmaputra valley. For a candidate, this is a high-scoring topic because the facts are dates, places and organisations that repeat year after year.
Petroleum: Asia's oldest oil story
The petroleum story of Assam begins at Digboi in Tinsukia district. Oil was first struck there in 1867, and commercial production began in 1889. Digboi is therefore the oldest oil field of India and the Digboi well No. 1 is regarded as the oldest oil well of Asia. The Digboi refinery is the oldest refinery in the country. The other major oil fields are Moran, Naharkatia and Lakwa. Exploration and production are mainly carried out by Oil India Limited (OIL) and the Oil and Natural Gas Corporation (ONGC), and the headquarters of OIL is at Duliajan in Dibrugarh district, which is also the state's largest oil-producing district. Assam produces roughly 3 million tonnes of crude oil a year.
Refineries and the petrochemical industry
Assam has four oil refineries: Digboi, Guwahati (established in 1962 by Indian Oil Corporation), Bongaigaon (established in 1979, located at Dhaligaon in Chirang district) and Numaligarh (established in 1999, the largest, with a capacity of about 3 million tonnes a year). The state's total installed refining capacity is about 7 million tonnes a year. The biggest petrochemical venture is the Assam Gas Cracker Project at Lepetkata near Dibrugarh, run by Brahmaputra Cracker and Polymer Limited (BCPL). Duliajan and the Dibrugarh region form the main petrochemical hub of the state.
Natural gas
Natural gas is found together with oil in the fields of the Brahmaputra valley. The Lakwa gas field in Sivasagar district is the largest gas field of Assam, and the biggest gas processing plant is at Duliajan. Gas is used for power generation, for fertiliser production and as a feedstock for petrochemical industries. This is what makes natural gas so valuable to the state: it does not only light homes and run industry, it also feeds the gas cracker that turns gas into plastics and polymers.
Coal
The main coal-producing district of Assam is Tinsukia, where the mines at Ledo, Margherita and Tipong are located. The Makum coalfield is the state's major coalfield, and the coal of the Margherita area is high-grade bituminous coking coal, which is used in industry as well as in thermal power. Tinsukia, and especially Margherita, is often called the 'coal city' of Assam because of these mines.
Limestone and cement
Limestone is found in the Karbi Anglong and Dima Hasao hills and in parts of Goalpara and Kamrup districts. The largest deposits are in the Kapili and Umrangso areas. Its main use is the production of cement, and the two cement plants that depend on it are at Bokajan in Karbi Anglong and Umrangso in Dima Hasao. Limestone is thus the mineral that links the hills of Assam to the construction industry of the whole region.
Other minerals and the Barak valley
Besides coal and petroleum, Assam has deposits of limestone, natural gas, crude oil, silica sand and several minor minerals. In the Barak valley, the main oil-bearing area is around Badarpur and Patharia in Karimganj district, and the valley also has its share of limestone and other resources. These deposits, though smaller than those of the Brahmaputra valley, are important for the local economy.
How to prepare this topic
- Fix the Digboi timeline first: oil struck in 1867, commercial production in 1889, refinery in 1901 and the first oil well of Asia.
- Memorise the four refineries with their years and places: Digboi, Guwahati 1962, Bongaigaon 1979 and Numaligarh 1999.
- Learn the agencies and their centres: OIL at Duliajan, ONGC, BCPL at Lepetkata.
- Link the minerals to districts: coal with Tinsukia (Makum, Margherita, Ledo), limestone with Karbi Anglong and Dima Hasao, gas with Sivasagar (Lakwa).
- Remember the figures: about 3 million tonnes of crude oil and about 7 million tonnes of refining capacity a year.
Common exam traps
- Digboi is the oldest oil field and also the site of the oldest refinery; do not mix it up with Numaligarh, which is the largest refinery.
- Oil was first struck in 1867, but commercial production started only in 1889 - the two years are often swapped.
- The Guwahati refinery was set up in 1962 by Indian Oil Corporation, and it is the second-oldest refinery of Assam after Digboi.
- Lakwa in Sivasagar is the largest gas field, while Duliajan has the largest gas processing plant - field and plant are different.
Frequently Asked Questions
Which is the oldest oil field and refinery of India, and where is it?
Both are at Digboi in Tinsukia district of Assam. Digboi is the oldest oil field of India, where oil was first struck in 1867 and commercial production began in 1889, and the Digboi refinery is the oldest refinery in the country. The Digboi well No. 1, drilled in 1867, is regarded as the oldest oil well of Asia, which makes Digboi one of the most important places in the industrial history of the region.
How many oil refineries are there in Assam and which is the largest?
Assam has four oil refineries: Digboi, Guwahati (1962), Bongaigaon (1979) and Numaligarh (1999). The Numaligarh Refinery Limited is the largest, with a capacity of about 3 million tonnes per year. The total installed refining capacity of the state is about 7 million tonnes per year, and the refineries are operated by Indian Oil Corporation and Numaligarh Refinery Limited.
Where is the headquarters of Oil India Limited and the largest gas field of Assam?
The headquarters of Oil India Limited is at Duliajan in Dibrugarh district, which is also the state's largest oil-producing district and the site of the biggest gas processing plant. The largest gas field of Assam, however, is the Lakwa gas field in Sivasagar district. Exploration and production in the state are carried out mainly by Oil India Limited and the Oil and Natural Gas Corporation.
Which district produces coal in Assam and what type of coal is found there?
Tinsukia district is the main coal-producing district of Assam, with mines at Ledo, Margherita and Tipong and the major Makum coalfield. The coal of the Margherita area is high-grade bituminous coking coal, useful both for industry and for thermal power. Because of these mines, Tinsukia, and especially Margherita, is often called the coal city of Assam.
Where is limestone found in Assam and what is it used for?
Limestone is found in the Karbi Anglong and Dima Hasao hills and in parts of Goalpara and Kamrup districts, with the largest deposits in the Kapili and Umrangso areas. Its main use is the production of cement, and the two cement plants that depend on it are at Bokajan in Karbi Anglong and Umrangso in Dima Hasao. Limestone is thus the mineral that links the hills of Assam to the construction industry.