04 July 2015, News Wires – The median annual water volume estimates for hydraulic fracturing in U.S. horizontal wells from 2000 to 2014 grew from approximately 177,000 gallons per oil and gas well to over 4 million gallons per oil well and 5.1 million gallons per gas well. But the amount of water required to fracture wells varies widely not only across the country, but within individual basins, according to a recent study from the U.S. Geological Survey (USGS).
The study, “Hydraulic fracturing water use variability in the United States and potential environmental implcations,” will be published in the scientific journal Water Resources Research. The study is the first national-scale analysis and map of hydraulic fracturing water usage in the United States.
USGS found that median water usage in vertical and directional wells remained below 671,000 gallons per well, slightly more than the 660,000 gallons that can be held in an Olympic-sized swimming pool.
Horizontal wells, which are drilled vertically and then directionally, generally require more water than vertical or directional wells. The study found that 52 out of the 57 watersheds with the highest average water use for hydraulic fracturing were watersheds where over 90 percent of wells were horizontally drilled.
“Although there has been an increase in the number of horizontal wells drilled since 2008, about 42 percent of new hydraulically fractured oil and gas wells completed in 2014 were still either vertical or directional,” according to a June 30 USGS press statement. “The ubiquity of the lower water-use vertical and directional wells explains, in part, why the amount of water used per well is so variable across the United States.”
Watersheds in the United States with the highest average water injected per oil and natural gas well generally coincide with shale gas areas, according to the USGS, including the Eagle Ford within watersheds located mainly in Texas, the Haynesville-Bossier within watersheds primarily in Texas and Louisiana, and the Barnett within watersheds mainly in Texas.
Other plays include:
- Fayetteville (within watersheds located in Arkansas)
- Woodford (within watersheds located mainly in Oklahoma)
- Tuscaloosa (within watersheds located in Louisiana & Mississippi)
- Marcellus & Utica (within watersheds located in parts of Ohio, Pennsylvania, West Virginia and within watersheds extending into southern New York)
Shale gas reservoirs are often fracked with slick water, but tight oil formations like the Bakken often used gel-based hydraulic fracturing treatment fluids, which generally contain lower amounts of water.
USGS conducted the research to understand the resource requirements and potential environmental impacts of unconventional oil and gas development.
“An important key to understanding how hydraulic fracturing could potentially impact the environment is the volume of water used in this process,” Tanya Gallegos, the study’s lead author, told Rigzone in an email statement. “The volume of water injected could affect the availability and consumptive use of freshwater sources, volumes of wastewater, the wastewater disposal and treatment procedures available, and the ultimate fate of this water.”
Coupled with local climate, geologic and hydrologic settings, and management practices, the regional differences is the amount of water injected for hydraulic fracturing translates into differences in the amounts of wastewater produced and ultimately differences in the potential for environmental impacts including water availability, water quality, wastewater disposal, and possibly wastewater injection-induced earthquakes, Gallegos said.