With North American oil and gas developments changing the energy landscape, Exxon Mobil said it expected shale to play a major role in global production. The U.S. Energy Department said technological breakthroughs in developing shale and other unconventional reserves were unlocking new energy potential. By the end of the decade, new technology could position the United States as a world energy leader. \"The growth results largely from a significant increase in onshore crude oil production, particularly from shale and other tight formations,\" an Energy Department report stated. An energy outlook report by Exxon Mobil said oil will remain the dominant form of fuel but natural gas is positioned to take the No. 2 spot from coal by 2025. \"Demand for natural gas will increase by about 65 percent through 2040, and 20 percent of global production will occur in North America, supported by growing supplies of gas from shale and other unconventional sources,\" the report read. Exxon said natural gas would account for about 30 percent of the global electricity generation by 2040, compared to less than 25 percent currently. Natural gas, the company added, emits 60 percent less carbon dioxide than coal when used for electricity.