Gas-rich shale areas often in water-scarce areas

WASHINGTON – Extracting natural gas for energy from shale rock deep underground requires lots of water, but much of the world’s shale gas is in regions where water is already scarce, according to a study issued Tuesday.

The amount of recoverable natural gas from shale formations would increase global reserves by nearly half, the report from the World Resources Institute found. That’s a potentially enormous boost for the international economy and for reduction of greenhouse gases that cause climate change, as gas used for power generation burns more cleanly than coal.

But increased oil and gas development raises thorny questions about how to allocate water in areas where it’s limited.

Gas from shale formations, long inaccessible because of their geology, has been unlocked in recent years by high-volume hydraulic fracturing, or fracking, which involves underground injection of millions of gallons of water mixed with sand and chemicals.

Worldwide, 38 percent of shale resources are located in regions “that are either arid or under high to extremely high levels of water stress,” the study says.

The picture for the United States is more varied. East Coast shale gas deposits are in areas that have historically had adequate amounts of water. But some of the most promising shale gas deposits in the West are in places where there is far greater competition for more limited water resources.

Overall, more than 35 percent of shale gas and oil resources in the U.S. are in areas that “are either arid or under high or extremely high baseline water stress,” according to the study.