The increasing number of hydraulic fracturing operations around the country has prompted concerns about its impact on the environment. Assessing these impacts has been difficult, partly because of a lack of timely, comprehensive data on hydraulic fracturing in general and on injected water volumes in particular. To track variation in water volumes across well types and geography, researchers from the U.S. Geological Survey created a national-scale map of injected water usage, a crucial step in assessing the potential environmental impact of hydraulic fracturing.
Hydraulic fracturing, or fracking, is a method used to extract oil and gas from petroleum reservoirs that can’t be tapped with traditional drilling techniques. The type of reservoir influences the type of fluids used and whether wells are drilled horizontally, vertically, or directionally (otherwise known as “slant” drilling). Many basins are developed using a combination of drilling directions.
Gallegos et al. examined data from over 263,800 oil and gas wells of all types, hydraulically fractured between 2000 and 2014. They found that water usage varied depending on the type of reservoir. On average, the highest volumes of water were injected into wells in shale gas areas, as opposed to coal bed methane, tight oil, or tight gas areas. (“Tight” oil and gas are contained in rock formations withlow permeability.)
Drilling direction also had an effect on water volume: Average water use in horizontal wells increased between 2000 and 2014, whereas the volume of water injected into vertical and directional wells remained steady. This helps to explain why water use is so variable across the nation and indicates that environmental impacts may be highly variable as well, depending on drilling operation methods and local factors.
Hydraulic fracturing draws water from local resources, so it can affect water availability, agricultural practices, and the behavior of waterways and the wildlife that depend on them. These effects are amplified in drought-prone regions. Hydraulic fracturing has also caused concern over potential contamination of drinking water by wastewater and fluids that can flow back to the surface after injection. Although wastewater is often disposed of in deep wells, this practice has become more contentious after being tied to induced seismicity in some areas.
This study contributes to a more complete knowledge of hydraulic fracturing. Understanding how drilling operations and opportunities for recycling affect the local environment is critical for local decision makers responsible for oil, gas, and water resources, wastewater disposal and treatment, and environmental management. (Water Resources Research, doi:10.1002/2015WR017278, 2015)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2015), Hydraulic fracturing water use is tied to environmental impact, Eos, 96, doi:10.1029/2015EO038705. Published on 4 November 2015.