Cairn India on Wednesday said it will invest about $2 billion in the country over the next 18 months for developing oil fields and building a pipeline that will deliver oil from Barmer in Rajasthan to the coastal areas of Gujarat. "Out of the $2 billion investment, $1.8 billion will go in Rajasthan alone and the remaining will be used for other blocks in other parts of the country,' Cairn India chairman Bill Gammell said at the company's annual general meeting here. Cairn India is developing three fields in Rajasthan