Concerns also have been raised about the possibility that hydraulic fracturing could contaminate the aquifers that supply drinking water.

WSJ: Daniel Yergin on the Shale Gas Revolution: Stepping on the Gas

The wider use of horizontal drilling and hydraulic fracturing, or fracking, has unleashed a vast supply of natural gas from the shale-rock formations across the U.S., forcing down domestic prices, cutting the need for overseas imports and making gas-exporting nations in Africa, Latin America and the Caribbean a less important piece in the U.S. energy puzzle.

WSJ: China's Xi Comes Calling on Americas

Hydraulic fracturing, or fracking, is under widespread development in the United States, fueling a natural gas supply boom, with an EPA review of its environmental safety underway.

FORBES: European Gas Giant Backs French Fear Of Fracking