DENVER, Dec 6 (Reuters) - Oilfield services firm Halliburton (HAL.N) on Monday said the world was headed for a period of oil scarcity following years of underinvestment in fossil fuel development. "I think that for the first time, in a long time, we will see a buyer looking for a barrel of oil, as opposed to a barrel of oil looking for a buyer," Halliburton Chief Executive Officer Jeff Miller said at an oil and gas conference in Houston.