According to the Ministry of Petroleum and Chemicals, India’s total onshore reserves of crude oil and natural gas are estimated at 1312.90 lakh tones and 59,240 lakh cubic meters respectively. Of these reserves, 692.70 lakh tones of crude oil are located in Assam and 620.20 lakh tones in Gujarat. Similarly these two regions have 42,460 lakh m and 16,780 lakh m of natural gas reserves respectively.
The ONGC and OIL estimate the total recoverable onshore reserves of crude oil at 1,750 lakh tones of which about 600 lakh tones have already been exploited. The Soviet geologist Kalinin estimated reserves of some 3 billion tons of crude oil on land and 1 billion tones on off shore in India.
Dr. N.B. Prasad estimated the total prognostic reserves of hydrocarbons of 12.70 billion tones in India of which about 6.20 billion tones in the form of crude oil and 6.5 billion tones of equivalent gas. The recoverable reserves include about 2 billion tons of crude oil and about 4 billion tones of equivalent gas. Of the estimated potential, about 59% belongs to Gujarat and the West Coast offshore areas and 38% to the eastern part of the country including Assam-Arakan belt, East Coast and offshore areas.
The recent prognosticated geological reserves of hydrocarbon are estimated at 21.31 billion tones of which the established reserves are only 532 billion tones. Half of the reserves are in the form of natural gas.
Similarly 61 per cent of the reserves lie in offshore zone (Vasudevan, 1993, p.59). There are three main areas of potential petroleum reserves in the country: (a) The Tarai zone running parallel to the Himalayas from Jammu and Kashmir to Assam; (b) River basins of the Ganga, Satluj etc including deltaic tracts of Ganga, Mahanadi, Godavari, Krishna and Kaveri; and (c) the continental shelf along the Western Coast, Gulf of Cambay and the islands in the Arabian sea, and the Bay of Bengal.