The following major oil-fields in India are yielding oil:
- The oldest (1882) and one of the largest (65 sq.km) oil-field in India at Digboi in Lakhimpur district of Assam, is still in production. Bappapung and Hunsapung are sister fields of Digboi.
- In the Surma valley Badarpur, Masimpur and Patharia yield poor quality oil.
- In upper Assam Naharkatiya (also Naharkatia), Rudrasagar, Moran, Hugrijan, Lakoa and Galeki have been developed by Oil India Ltd. On the occasion of 50th anniversary of Oil India Limited, the oil fields at Naharkatiya was given a heritage tag by the Chief Minister of Assam.
- Refineries for Assam crude are at Digboi, Guwahati (Nunmati) and Bongaigaon, connected by a pipeline which also carry crude to Barauni refinery in Bihar. The pipeline is 1,150 km long. Barauni is also linked by pipelines with Haldia and Kanpur.
- Gujarat’s oil wells are at Amkleswar (largest), Cambay, Kalol, Kosamba, Mehsana, Nowgam, Dholka, Lunej, Sananda, Wavel Bakal and Kathana.
The Gujarat crude is refined at Kayali (Koyali) refinery (now second largest refinery in India) which is linked by pipes to its several tributary fields. Mathura, will receive imported crude from Salaya, a new port in the Gulf of Kutch.
- The Bombay High out in the Arabian sea, 152 km north-west of Bombay city, has rich deposits of oil and gas, which are being sent by submarine pipelines to Uran of the mainland.
The oil field regions of India are:
- Eastern Assam,
- Arunachal Pradesh,
- Southern West Bengal,
- Himachal Pradesh,
- Uttar Pradesh
- Tarai region
- Bombay High
- Goa and
- Kaveri, Godavari and Mahanadi deltas and
- Andaman and Nicobar Islands.
These regions were all under shallow seas, some 70 million years ago, i.e., just before the birth of the Himalayas. Oil and gas may have seeped out of some of these areas. Hence oil prospecting is being carried on to find out the actual, oil pools.
- In 1959, Oil India Limited was formed as a joint undertaking of Burmah Oil Company and the Government of India (GOI). Later on, in 1981, it became a subsidiary of GOI. At present, Oil India is a listed company and the GOI share-holding stands at 67.64%.