But critics of shale gas point to environmental concerns such as high water use and possible water contamination, the release of methane and, to a lesser extent, earth tremors caused by drilling.

BBC: US oil production 'to jump by a quarter by 2014'

Environmental issues such as clean air and water are major concerns of voters as this year's elections approach, according to a poll conducted for the League of Conservation Voters.

CNN: Environment is crucial issue for voters, poll shows

The main obstacles cited by the energy executives surveyed speak for themselves: opposition to expanded drilling in places such as the Arctic National Wildlife Refuge (cited by 33%), environmental concerns (16%) and a lack of investment in energy due to low commodity prices (14%).

FORBES: U.S. Energy Independence in 15 Years?