British energy firm Cairn Energy Plc will invest $100 to $150 million to start production in the recent oil discovery in the Thar desert in Rajasthan, billed as India's largest on-land oil discovery in two decades.

 While commercial production of crude oil from the N-B-1 well, which is estimated to hold 50-200 million barrel of reserves, will take three-and-half years, the firm plans to put into production two smaller fields, discovered earlier in the same Barmer block, in a year's time.

'Rajasthan oil find looked like West Texas'

"Developing the N-B-1 oil find may take anything between $100 to $150 million," Cairn Energy chief executive Bill

Gammell said after Petroleum Minister Ram Naik named the oil find as 'Mangala', meaning auspicious.

Last month, Cairn announced it found an estimated in-place reserves of between 450 million and 1.1 billion barrels of oil, of which 50 million to 200 million barrels can be recovered, in its Barmer block in Rajasthan. A test well showed a cumulative flow rate of 6,000 barrels a day.

Gammell said the company plans to drill three or four appraisal wells in the next few months in Rajasthan to "better understand the oil find."

Cairn Energy India Pty Ltd chairman Philip Tracy said the earlier Raageshwari and Saraswati discoveries, estimated to hold about 14 million tonnes and 21 million tonnes of crude oil respectively, will be put on production in a year.