Energy companies drilling in 10 onshore basins across the country used nearly 250 billion gallons of water over a 10-year period to extract unconventional natural gas and oil, a large number but still less than 1% of the total amount of industrial water used nationwide, a Duke University study has found.
During the study period, 2005 to 2014, fractured (fracked) wells drilled in 10 basins studied also generated an estimated 210 billion gallons of wastewater, researchers calculated in a report published Tuesday.
"Water use and wastewater production are two of the chief environmental concerns voiced about hydraulic fracturing," said Duke's Avner Vengosh, professor of geochemistry/water quality at the Nicholas School of the Environment. "Yet until now, we've had only a fragmented and incomplete understanding of how much water is actually being used, and how much wastewater is being produced."
Vengosh and Duke doctoral candidate Andrew Kondash published their peer-reviewed "The Water Footprint of Hydraulic Fracturing" in the journal Environmental Science & Technology Letters. Funding was provided by a National Science Foundation grant and the Duke University Energy Initiative.
Unconventional drilling requires more water use than conventional drilling, but compared to other energy extraction methods, fracking wells is less water-intensive overall. According to Duke, underground coal and uranium mining, along with enhanced oil recovery "use between two and a half to 13 times more water per unit of energy produced."
Fracked oil wells were found to generate about one-half of a barrel of wastewater for every 1 bbl of oil, while conventional oil wells drilled on land generated more than three wastewater barrels for every 1 bbl of oil.
The integrated data used "multiple government and industry sources" offering what Vengosh said was "the first comprehensive assessment" of the total water footprint for fracking, both nationally and for each of 10 major U.S. shale gas or tight oil basins.
"While hydraulic fracturing consumes only a small fraction of the water used in other extraction methods, our analysis highlights the fact that it can still pose serious risks to local water supplies, especially in drought-prone regions such as the Barnett formation in Texas, where exploration and development is rapidly intensifying," Kondash said. "Drilling a single well can require between 3-6 million gallons of water, and thousands of wells are fracked each year. Local water shortages could limit future production."
Finding ways to treat and dispose/recycle chemical-laden flowback water and brine-laden wastewater produced over the lifetime of an unconventional well poses challenges.
"Given the high levels of contaminants these waters contain, it's startling that the amount of wastewater being produced from hydraulic fracturing in the United States is nearly on the same level as the amount of water used to frack the wells in the first place," Vengosh said. "Yet the quality of the water that comes out is very much different from the water the goes in."
Duke's study indicated that water usage has been low in fracked wells, but the amount of water required to frack wells has been increasing dramatically every year, according to a report issued this summer by the U.S. Geological Survey (USGS) (see Shale Daily, July 1). Within watersheds across the United States, the average amount of water used for fracking in the seven major basins ranged from as little as 2,600 gallons/well to as much as 9.7 million gallons/well. The USGS compilation, the first nationwide map of usage, relied on IHS Inc. data on 81,000 wells across the country in the big seven shales: Eagle Ford, Haynesville/Bossier, Barnett, Fayetteville, Woodford, Tuscaloosa Marine and Marcellus/Utica.
Separately, the Environmental Protection Agency in April said Texas, the country's largest producer, also is No. 1 in the amount of water producers use to produce oil and gas, followed by Pennsylvania, based on the FracFocus Chemical Disclosure Registry by operators in 20 states (see Shale Daily, April 7).
Kondash and Vengosh said they culled numbers for their report using data from the Energy Information Administration, state agencies, industry reports, FracFocus and DrillingInfo.com. Although the Duke paper looks only at U.S. data, its methodology and findings could be used to project future water use and wastewater volume from fracking in other energy basins worldwide, the researchers said.