Mineral Resources of Assam - Pertroleum Oil: Assam Geography
Assam is rich in mineral resources and Petroleum or crude oil is one of the most important of them all. In India, petroleum was first discovered in Assam and the first Oil Refinery in Asia came up at Digboi in Assam.
Mineral Oil/Petroleum in Assam
Like coal, mineral oil also occurs mainly in the Upper Assam region of the Brahmaputra Valley. In Assam at the present time, the quest for oil has been directed in the northeast of the Brahmaputra Valley and the broad belt of Tertiary rocks extending from the Moiban range in Arunachal Pradesh to Tripura through Cachar district and Mizoram. Oil is found in three stratigraphical horizons in the geological column. Prior to the discovery of oil fields in recent years at Naharkatia, Hugrijan, Rudrasagar, Moran, Lakwa, etc., Digboi was the only oil field in independent India. The discovery oil in the Digboi area took place in 1886,when on the recommendation of the Late H.B. Medlicott, of the Geological Survey of India,drilling for oil was also started near Margherita and Jaipur. These borings met with partial success and due to poor production rates and lack of good communication, no interest was paid on them. The availability of coal in that area led to construction of a railway line from Ledo to Dibrugarh for the purpose of carrying the same, the presence of an oil show near Digboi was discovered by chance. The drilling of the first well was completed in 1890, which gave 200 gallons (908 liters) of oil per day. Within nine years (in 1899), fourteen wells had been drilled. In 1899, the Assam Oil Company was formed to take over the management of the
oil interest in this area. In 1921, the Burma Oil Company took over the commercial and technical management, giving it much needed financial assistance,up-to-date equipment and modern transport and refining facilities. In about ten years time,the production had stepped up to 180,000 gallons (8,18,273 liters)per day compared to about 12,000 14,000 gallons (55,550-63,640 liters)per day before 1921.
During 1931,the Digboi oil field met about 11.5% of the crude requirements of the then undivided Indian Empire,which included Burma.
After failures to find oil at Namphuk, Namchik, Makum-Namdang, Barjan, Dhekiajuli, Barsilla, Bandersulia, Nichuguard,etc.,efforts were made to find additional oil fields in the alluvial areas of the Assam Valley. Drilling in the Upper Assam Valley, on the basis of the results of geophysical and regional geological survey,has shown that the Barail rocks, from which the oil has migrated into upper Tipam sands in Digboi, is also oil-bearing in the Naharkatia-Hugrijan area at the depth of about 10,000 (3048 metres )feet. The first well in this area was competed in 1953 and the area so far explored by drilling stretches between 10 to 20 miles (16 to 32 kilometres) west of Digboi. At Moran ,about 20 miles(32 kilometres), further west from Naharkatiya the first test-well was successfully completed in 1956 and production was proved in the same rock Groups as at Naharkatiya. Further drilling in the Naharkatia-Hugrijan area,where 30 wells were completed upto the end of 1957,had already proved a potential of nearly 2.5 million tons of oil per year together with about 45 to 50 million cu.ft.(21.66 to 35.12 million. cu.m.) gas per day.
The discovery of oil at Naharkatia in 1953, has radically changed the prospects for oil in Assam. In earlier period, oil was found in higher horizons, namely in Tipams and the Surmas, although a little was also found in the top of the Barails and in sharply folded anticlines, whereas at Naharkatiya oil was found in the Barails in very gently folded beds with definite dips on the flanks but rather indefinite pitches, and oil was found not only in structural traps but also in fault traps and especially in areas with a thick cover of alluvium and at greater depth than tested before. In fact, the whole of the alluvial tract in Upper Assam has become oil prospective. In the Naharkatiya oilfield (including Moran), the reserves of crude oil are estimated at 47 million metric tonnes and of associated and dry gas 7,90,000 million cubic feet.
Mineral oil was also found in Cachar district within the former Surma Valley. Petroleum is reported to occur in the Patharia Reserve Forest. In the Badarpur-Masimpar field, petroleum was obtained from the Bhuban stage of the Surma Group. The first well was actively proposed by the Burma Oil Company Ltd. for 18 years from 1915 to 1933,but oilbearings sands were of restricted extent and their exhaustion led to the final abandonment of the field. The Company drilled 63 wells obtained 1,864,000 barrels of crude oil which was refined at the Digboi refinery. Statement below shows the production of crude oil and natural gas from the oil fields of Assam.