USGS: Water Used in Hydraulic Fracturing Varies Greatly

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Written by John Egan for Industrial Info Resources (Sugar Land, Texas)--Oil & Gas Production uses a large but highly variable amount of water, according to a recent report from the U.S. Geological Survey (USGS) (Reston, Virginia), a branch of the Department of the Interior (DOI) (Washington, D.C.). In its first-ever assessment of water used in hydraulic fracturing, USGS found average water use for wells drilled horizontally rose from about 177,000 gallons per well in 2000, to between 4 million gallons per oil well and 5.1 million gallons per gas well in 2014. By contrast, wells that were drilled vertically or directionally used substantially less water, less than 671,000 gallons on average--about the amount of water held by an Olympic-sized swimming pool.

The amount of water used for hydraulic fracturing in different watersheds across the U.S. range from as little as 2,600 gallons per well to as much as 9.7 million gallons per well. Hydraulic fracturing is used to varying degrees in wells that are drilled vertically, directionally and horizontally.

Click on the images on the right for a map of average water use per hydraulically fractured wells, and for a second map showing the percentage of hydraulically fractured wells that are drilled horizontally.

Although hydraulic fracturing of horizontally drilled oil and gas wells has garnered a lot of media and public attention in recent years, the USGS study found that vertically or directionally drilled wells that were hydraulically fractured still accounted for a sizable percentage of all wells drilled; about 42% of all wells completed in 2014 were drilled either vertically or directionally.

The continued ubiquity of the lower-water-use vertical and directional wells explains, in part, why the amount of water used per well varies so widely across the U.S., the agency noted. Wells that were horizontally drilled and hydraulically fractured generally required more water than wells that were vertically or directionally drilled, the agency added: In 52 out of the 57 U.S. watersheds with the highest average water use for hydraulic fracturing, more than 90% of the wells were horizontally drilled.

Click on the image at right for a graphic showing average water used to hydraulically fracture oil and gas wells that were drilled horizontally, vertically and directionally, and the number of those wells drilled in the U.S. from 2000 through August 2014.

Some operators are experimenting with water-less fracking techniques, but initial results reportedly have been disappointing.

In its study, titled "Hydraulic Fracturing Water Use Variability in the United States and Potential Environmental Implications," USGS noted that "hydraulic fracturing is not a one-size-fits-all operation, (and) assumptions and generalizations regarding water use in hydraulic fracturing operations and the potential for environmental impacts should be made with caution." USGS scientist Tanya Gallegos, the study's lead author, added: "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. 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."

The USGS study was published earlier this summer in Water Resources Research, a journal from the American Geophysical Union (Washington, D.C.). It noted the amount of water used in hydraulic fracturing depended on a variety of factors, including whether oil or gas was being extracted, and the local or regional characteristics of the reservoir itself. Other factors included the reservoir extent, depth, and thickness of oil-bearing or gas-bearing strata, as well as the porosity, permeability, temperature, pressure and other intrinsic properties of the formation itself.

For example, tight oil typically is extracted from the Bakken Shale in North Dakota with gel-based hydraulic fracturing fluids, which use proportionately less water than the slick water fluids used to extract gas from other shale formations.

The study identified the watersheds where the most water was used to hydraulically fracture wells. Those watersheds coincided with parts of the following shale formations:

• Eagle Ford
• Haynesville-Bossier
• Barnett
• Fayetteville
• Woodford
• Tuscaloosa
• Marcellus and Utica

USGS pointed out that this list was not rank-ordered. In other words, it did not say producers in the Eagle Ford shale used more water per well or in aggregate than operators in the Marcellus and Utica shales.

Using drilling data supplied by a unit of IHS Incorporated (NYSE:IHS) (Englewood, Colorado), the analysis noted many oil and gas resources within a given basin are developed using a mix of horizontal, vertical and directional wells. The variability in hydraulic fracturing water use may have public-policy consequences, USGS noted.

"Hydraulic fracturing and horizontal drilling pose significant public-policy issues for regulators, operators, elected officials and the general public," said Jesus Davis, Industrial Info's vice president of research for the Oil & Gas Production, Pipelines and Terminals industries. "The amount of water used by drillers, and what happens to that water after it is used, are two of the important issues being tackled across the country. By showing that hydraulic fracturing is not a one-size-fits-all proposition, the USGS report can help elevate the rigor of these public-policy discussions."

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