Hydraulic Fracturing

Featured: Shale-gas production & groundwater quality, Marcellus Shale

Featured: Shale-gas production & groundwater quality, Marcellus Shale

A new USGS study reports that shale-gas production in northern Pennsylvania has not currently caused widespread hydrocarbon contamination in the upland aquifer zone used for domestic supply, but it's too soon for a full assessment.

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Featured: Bakken Shale oil- and gas-production and groundwater quality

Featured: Bakken Shale oil- and gas-production and groundwater quality

Shale-oil and -gas production from a major production area in Montana, North Dakota, and South Dakota has not caused widespread hydrocarbon contamination to date in nearby aquifer zones used for drinking-water supply, reports a new USGS study.

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Science Center Objects

Hydraulic fracturing, commonly known as fracking, is the process of injecting water, sand, and/or chemicals into a well to break up underground bedrock to free up oil or gas reserves. The USGS monitors the environmental impact of this practice across the country, from potential earthquakes to degraded groundwater quality.


Hydraulic fracturing (informally known as hydrofracking, fracking, fracing, or hydrofracturing) is a process that typically involves injecting water, sand, and chemicals under high pressure into a bedrock formation via a well. This process is intended to create new fractures in the rock as well as increase the size, extent, and connectivity of existing fractures in order to extract trapped oil and gas.

Hydraulic fracturing is a well-stimulation technique used commonly in low-permeability rocks like tight sandstone, shale, and some coal beds to increase oil and/or gas flow to a well from petroleum-bearing rock formations. A similar technique is used to create improved permeability in underground geothermal reservoirs. A form of hydraulic fracturing is also used in low permeability sediments and other tight subsurface formations to increase the efficiency of soil vapor extraction and other technologies used in remediating contaminated sites.

Image: Brown Fracking Sand

Frac sand is a specialized type of sand that is added to fracking fluids that are injected into unconventional oil and gas wells during hydraulic fracturing. Frac sand keep induced fractures open and extend the time and flow rate of oil and gas from a well. (Credit: John Jackson, USGS)


The actual practice of fracking is only a small part of the overall process of drilling, completing, and producing an oil and gas well. However, since fracking involves injecting a chemical solution into the ground to free up oil and gas resources, there are some potential environmental impacts related to this process. These include:

  • spills of chemicals at the surface
  • surface-water-quality degradation from waste fluid disposal
  • groundwater quality contamination
  • induced seismicity from the injection of waste fluids into deep disposal wells



Through an agreement among the Department of the Interior, the Department of Energy, and the Environmental Protection Agency, the USGS plays a large role in improving our scientific understanding of the environmental issues related to unconventional oil and gas. The scientific data provided by the USGS are crucial in helping Federal and State resource managers meet the challenge of balancing America’s needs for energy resources and a clean and healthy environment.



U.S. Environmental Protection Agency

U.S. Department of Energy