The very first national-scale analysis and map of hydraulic fracturing water usage was recently created by the U.S. Geological Survey (USGS) and accepted for publication by Water Resources Research, a journal of the American Geophysical Union. Researchers found the amount of water needed to hydraulically fracture oil and gas wells varies significantly across the country, ranging from 2,600 gallons to 9.7 million gallons per well.
Additionally, during the 14-year period from 2000-2014, median annual water volume estimates for hydraulic fracturing in horizontal wells increased from 177,000 gallons per oil and gas well to over 4 million gallons per oil well and 5.1 million gallons per gas well. However, median water use in vertical and directional wells is less than 671,000 gallons per well.
What Causes Water Use to Vary?
“One of the most important things we found was that the amount of water used per well varies quite a bit, even within a single oil and gas basin,” said the lead author of the study, USGS Scientist Tanya Gallegos. “This is important for land and resource managers, because a better understanding of the volumes of water injected for hydraulic fracturing could be a key to understanding the potential for some environmental impacts.”
Horizontal wells are drilled vertically or directionally to access the unconventional oil or gas reservoir. They’re then drilled laterally along the oil or gas-bearing rock layers to heighten contact with the reservoir rock and fuel greater oil or gas production than can be realized solely with vertical wells. Of course, they also use substantially more water than their vertical or directional counterparts, so that must be taken into account.
The number of horizontal wells drilled since 2008 has been on the rise. However, 42% of new hydraulically fractured oil and gas wells finished in 2014 were vertical or directional. The omnipresence of lower-water-use vertical and directional wells partially explains why the total amount of water used per well varies so widely across the country.
Shale Reservoirs Coincide with High-Use Watersheds
The watersheds using the most water to hydraulically fracture wells on average overlapped with a number of shale formations, including Eagle Ford, Haynesville-Bossier, Barnett, Fayetteville, Woodford, Tuscaloosa, Marcellus and Utica. Shale reservoirs are commonly fractured with slick water — a type of fluid necessitating a great deal of water. Conversely, tight oil formations commonly use gel-based hydraulic fracturing treatment fluids that usually contain much less water.
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