Oil India Limited (OIL) is a central public sector undertaking under the ownership of Ministry of Petroleum and Natural Gas, Government of India. The Ministry of Petroleum and Natural Gas oversees its operations, with its headquarters in Duliajan, Assam. The central public sector undertaking is a Navratna with its offices in Duliajan, Noida, Guwahati and Jodhpur. OIL is engaged in the business of exploration, development and production of crude oil and natural gas, transportation of crude oil and production of liquid petroleum gas. The company's history spans the discovery of crude oil in India in the year 1889, this was second in the World in the far east of India at Digboi and Naharkatiya, Assam to its present status as a fully integrated upstream petroleum company presently operating in more than 9 locations overseas. Recently, OIL acquired majority shares in Numaligarh Refinery Limited from Bharat Petroleum Corporation Limited , thus making Numaligarh Refinery Limited a subsidiary of OIL. Exploration and production Oil India Limited was formed by the Burmah Oil Company Limited as its subsidiary in India 1887 to explore in the Assam Basin, India (Corley, T A B, 1983, The History of the Burmah Oil Company, 1886–1983). Staff at the Burmah Oil Company Limited had heard from a geologist with the colonial British Indian Geological Survey, Thomas Oldham, that oil was found on the feet of elephants that were being used as beasts of burden in the vicinity of the Digboi village (Arun Metrie, pers. comm., former Burmah Oil economist, 1988). The oil on the elephants' feet was traced to the Digboi area, where a surface fold (anticline in geological parlance) had formed a broad hill. A successful technique for exploration for hydrocarbons at the time was drilling beneath seeps on anticlines (Thornton, S E, 2015, The history of Oil Exploration in the Union of Myanmar, Paper No. 10807), so Oil India drilled beneath the Digboi seeps and found a giant oil field. Several other oil fields were subsequently found by Oil India Limited in what became India's first oil production. Recoverable oil reserves. the company produced 3.466 MMT of crude oil, 2625.81 million cubic metre at standard conditions of natural gas and 46,640 tonnes of LPG. Most of this was produced from its traditionally rich oil and gas fields concentrated in the Northeastern part of India and contribute around 80% of total oil and gas produced in the