Sri Lanka, battered by four decades of Tamil separatist violence that ended a year ago, appears finally able to begin to exploit its sizable domestic oil and gas sources and reduce its crippling dependence on imports. In one of the latest moves, Cairn Lanka, a subsidiary of the Edinburg-based Cairn Energy PLC, will begin a three-well drilling campaign off the Mannar Basin, located between southwestern Sri Lanka and the Indian coastline in the first quarter of next year, according to the British High Commission in Colombo.