Cairn India may increase investment into joint venture Rajasthan oilfields, the largest crude oil well in India, as the board of Oil and Natural Gas Corporation (ONGC) has given its necessary approval for the plan on Monday, ending all speculations of state run firm's participation in the JV.

Earlier, Cairn India, having 70 per cent stakes in the JV, fixed Rs 13,756 crore to develop the Mangala, Bhagyam and Aishwariya fields in Rajasthan. However, the Indian unit of Britain's Cairn Energy revised the total cost to Rs 16,902-17,840 crore to make it economically viable for both firms.

The state run Oil firm ONGC had expressed reservations to Cairn's revised field development plan as it was entitled to pay the entire royalty despite having 30 percent stakes in the JV. An ONGC official said, "ONGC's liability to pay royalty to Rajasthan on 100 per cent production works out to $36 per barrel at a price of $60 per barrel."

The Rajasthan oil field block is likely to become fully operational in this month. Mangala field, with initial capacity of around 30,000 barrels a day, is expected to produce up to 80,000 barrels of crude oil by the end of current year.

India, the third-largest oil consumer of Asia, has been exploring new gas and oil reservoirs to cut its import bill by decreasing it dependence on crude oil import.