Energy companies used nearly 250 billion gallons of water to extract unconventional shale gas and oil from hydraulically fractured wells in the US between 2005 and 2014, according to the study. During the same period, the fracked wells generated about 210 billion gallons of wastewater.
The study, which integrates data from multiple government and industry sources, is the first comprehensive assessment of fracking’s total water footprint nationally and for each of the 10 major US shale gas or tight oil basins. The findings were published in the journal Environmental Science & Technology Letters.
While fracking an unconventional shale gas or oil well takes much more water than drilling a conventional oil or gas well, compared to other energy extraction methods, fracking is less water-intensive in the long run, the researchers found.
Underground coal and uranium mining and oil recovery enhancement extraction uses between two-and-a-half to 13 times more water per unit of energy produced.
The study also found that fracked oil wells generate about half a barrel of wastewater for each barrel of oil, while conventional oil wells on land generate more than three barrels of wastewater per barrel of oil.
Although hydraulic fracturing consumes only a small percentage of the water used in other extraction methods, it can still pose serious risks to local water supplies, especially in drought-prone regions, the researchers said.
Finding ways to treat and dispose of or recycle chemical-laden flowback water and brine-laden wastewater that is produced over the lifetime of an unconventional oil or gas well also poses challenges.