In order for hydraulic fracturing and production in the Eagle Ford to continue, a great deal of water is required. Early on during the process, scientists looked at questions related to the water-energy nexus:
- How much water was used during the 2009–2013 period of exponential growth in energy production?
- How does the volume of water used during hydraulic fracturing compare to more conventional energy production?
- Is water scarcity an issue for continued energy production?
- What are the local competing demands on water? and,
- Are there more sustainable practices that can address water constraints?
Early Research Findings on Water Usage in the Eagle Ford Shale
We are using more water for oil and gas production derived from unconventional reservoirs because we are producing more oil and gas, not because hydraulic fracturing requires more water per unit of energy production. We can manage water use more sustainably by recycling water, using brackish groundwater, and reducing competition with freshwater users, such as irrigators and municipalities.1Scanlon, B. (2015, June 1). Water for shale oil and gas production: Can it be managed more sustainably? The Cynthia & George Mitchell Foundation Blog
Dr. Bridget Scanlon
Senior Research Scientist, Bureau of Economic Geology, The University of Texas at AustinLet’s take a look at some of the detailed findings from Dr. Scanlon’s team that contributed to her statement. These quotes are highlights2Scanlon, B. (2015, June 1). Water for shale oil and gas production: Can it be managed more sustainably? The Cynthia & George Mitchell Foundation Blog of their study.
Between 2009 and 2013, at the onset of the shale boom in the Eagle Ford, 40 billion gallons of water were used in the 8,300 wells drilled in the Eagle Ford, and a projected 330 billion gallons of water will be needed over the next 20 years.
Unconventional, hydraulic fracturing generally uses from 0.4 to 1.4 gallons of water to produce a gallon of oil, which is in the lower range of that used in conventional reservoirs in the U.S. (where the range is from 0.1 to 5 gallons of water per gallon of oil produced). The difference is in the timing of water use over the ~20 year production life of a well. Most of the water use in hydraulic fracturing is in the early stages at well completion versus later stages in conventional reservoirs for water flooding and enhanced oil recovery.
Reliance on fresh, potable water is not sustainable and competes with other needs and requirements. Recycling produced water is a more sustainable practice growing in application by some operators. Brackish groundwater is widely available in Texas aquifers with an estimated 80,000 billion gallons in the Eagle Ford Shale play. That’s ~250x the projected need for hydraulic fracturing.
Water scarcity should not be a concern to the industry, and hydraulic fracturing will not significantly impact other water users, except in Dimmit and Zavala counties in the northwest of the Eagle Ford area where irrigation demand is the dominant water use sector.
The volume of water used for gas extraction is ~6% of the water consumed in power production. In addition, use of natural gas in combined cycle power plants saves water when compared to water use in steam turbine coal, nuclear, and other older natural gas power plant technologies. We estimated that for every gallon of water used for unconventional shale gas extraction in 2011 we saved 330 gallons of water by generating power using natural gas rather than coal or nuclear fuels.
USGS Assessment of the Eagle Ford
With further data and exploration, the United States Geological Survey (USGS) followed up with some new numbers. In 2018, the USGS assessed potential quantities of oil and gas resources that could be produced in the Eagle Ford Group, estimating a mean of 8.5 billion barrels of oil, 66 trillion cubic feet of natural gas, and 1.9 billion barrels of natural gas liquids.3USGS. (2020, October 14). Mixing oil and water. United States Geological Survey. https://www.usgs.gov/news/mixing-oil-and-water
USGS scientists drilling a research core near Waco, Texas. This core was drilled during field work for an oil and gas assessment for the Eagle Ford of the Gulf Coast Basins.
Water Usage
The USGS estimates that, to produce the full amount of the continuous oil and gas resources of the Eagle Ford Group, a mean of about 672 billion gallons of water will be needed for the hydraulic fracturing process. The agency also estimates that a mean of about 16 billion gallons of water would be required to complete the drilling and cement process to produce the oil and gas in the Eagle Ford Group.4USGS. (2020, October 14). Mixing oil and water. United States Geological Survey. https://www.usgs.gov/news/mixing-oil-and-water
Produced Water
The USGS estimates that during production of the oil and gas in the Eagle Ford Group, a mean of about 177 billion gallons of produced waters could be brought up along with the oil and gas.5USGS. (2020, October 14). Mixing oil and water. United States Geological Survey. https://www.usgs.gov/news/mixing-oil-and-water
What Water Should be Used?
Scientists generally agree that the best solution is the use of brackish water sources for production in the Eagle Ford, to mitigate freshwater aquifer depletion, already vulnerable to irrigation in the area. Additionally, reusing produced water well help with the impact.6Hiller, J. (2015, July 11). Water use increases in the Eagle Ford. Houston Chronicle. https://www.houstonchronicle.com/business/energy/article/Water-use-increases-in-the-Eagle-Ford-6378892.php.
Schematic of Eagle Ford play area. Only one aquifer is shown for clarity and includes an up-dip recharge zone where the aquifer outcrops, and a downdip confined section that includes brackish water shown in red. A representative hydraulically fractured well is shown with mean depth of ~2 miles (3.2 km) and mean lateral length of ~1 mi (1.6 km). A nearby injection well is shown where flowback-produced water can be disposed. Irrigation is mostly up-gradient from the Eagle Ford hydraulic fracturing operations and is represented by center pivot irrigation circles representative of the area around Dimmit and Zavala counties, known for its year-round production of vegetables by irrigation. A power generation station is included to represent net impacts of natural gas on water resources including water cooling through power generation and water creation from natural gas combustion.7caption after: Scanlon, B. R., Reedy, R. C., & Nicot, J. P. (2014). Will water scarcity in semiarid regions limit hydraulic fracturing of shale plays?. Environmental Research Letters, 9(12), 124011.
Career Spotlight: Dr. Bridget Scanlon
Academic Background
- B.S. Geology, Trinity College, Dublin, Ireland, 1980
- M.S. Geology, University of Alabama, 1983
- Ph.D. Geology, University of Kentucky, 1985
Dr. Bridget Scanlon, Senior Research Scientist at The University of Texas at Austin’s Bureau of Economic Geology, leads the Sustainable Water Resources Program. The research group examines a number of water-related issues, including groundwater recharge, impact of climate change on water resources, and groundwater contamination.8Bureau of Economic Geology. (n.d.). Dr. Bridget R. Scanlon. Bureau of Economic Geology. https://www.beg.utexas.edu/people/bridget-scanlon.
Dr. Scanlon’s work on aquifer recharge estimation methods, water use in energy production, impacts of land-use change, and the global recharge estimates for water-scarce regions has improved the understanding of groundwater depletion worldwide. Much of her work combines a variety of analysis methods—from local field measurements to data from NASA’s GRACE satellite—to provide insight on water in the environment at a variety of scales. Recently, Dr. Scanlon led the most comprehensive study to date on the water supply of the Colorado River Basin, a water source for over 40 million people.9Texas Geosciences. (2016, February 9). Bridget Scanlon elected to National Academy of Engineering. https://www.jsg.utexas.edu/news/2016/02/bridget-scanlon-elected-to-national-academy-of-engineering/
In 2016, Dr. Scanlon was elected to the National Academy of Engineering, one of the highest professional honors accorded to engineers and scientists, for her contributions to the evaluation of groundwater recharge and aquifer depletion. Members are elected to the academy based on their record of accomplishments in the engineering field and their professional integrity. Those who rely on her work include policy makers, regulators, city planners, energy companies and nongovernmental organizations.10Texas Geosciences. (2016, February 9). Bridget Scanlon elected to National Academy of Engineering. https://www.jsg.utexas.edu/news/2016/02/bridget-scanlon-elected-to-national-academy-of-engineering/
Image Credits
- EFWaco091415-USGS-Stan-Paxton: Stan Paxton, U.S. Geological Survey
- Scanlon-BEG-Pont-du-Gard: The University of Texas at Austin