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U.S. Geological Survey

Introduction to Hydraulic Fracturing

Also known as hydrofracking, fracking, or hydrofracturing, hydraulic fracturing is an oil and gas well development process that involves injecting water under high pressure into a bedrock formation via the well. It is used to increase oil and/or gas flow to a well from petroleum-bearing rock formations that is seeing increasing use across the country. Here’s a look at how USGS science informs the discussion regarding the potential opportunities and impacts from hydraulic fracturing and related practices, such as horizontal drilling and deepwell fluid injection.

Water Use and Water Quality

A Marcellus Shale Outcrop
A Marcellus Shale outcrop in Highland County, Virginia, shows at the surface the object of shale gas development drilling in nearby states.

Energy development often requires substantial amounts of water, and hydraulic fracturing is no exception. Water is needed not only for the traditional drilling process, but also for the actual fracturing as well. Water is first mixed with chemicals and fine sands, then pumped at extremely high pressure into the shale rock to fracture it, forming pathways for the oil and gas to reach the well. The water is then recovered, along with the oil and gas. USGS is conducting studies to assess the amount of water required for hydraulic fracturing as well as the impacts of withdrawing water from the local environment. On-the-ground projects are currently proposed or ongoing in more than 15 States to establish baseline water quantity and quality measurements and assessments.

In addition, oil and gas formations themselves often contain significant amounts of water that come up with the petroleum: this is referred to as produced water. Produced waters contain dissolved trace minerals from their formations of origin. USGS is studying the impacts of produced waters on local environments as might result from a variety of energy development techniques. In fact, USGS recently published a new national produced waters geochemical database, updating the older one with more than 100,000 new samples from all over the country.

Concerns also exist regarding the potential contamination of fresh groundwater resources from oil and gas extraction wells that use hydraulic fracturing; either from the petroleum resource being produced or from the chemicals introduced in the fracturing process. USGS is studying well water quality in several states where hydraulic fracturing is being practiced, including Arkansas, New York, Pennsylvania, and Wyoming.

Blowout Preventer Control System
Control system for blow-out preventers at a drill pad in the Fayetteville Shale gas play in Arkansas.

Energy Assessments

Hydraulic fracturing, directional drilling, and other advanced technologies have allowed the production of oil and gas from rock formations that previously could not be developed. As a result, so-called “unconventional” resources like shale gas and shale oil are among the fastest growing energy sources in the United States. And unconventional gas now accounts for well over 60 percent of the U.S. gas supply. The USGS has long assessed the amount of oil and gas yet to be discovered using standard industry practices and geologic knowledge at the time of the assessment. High volume hydraulic fracturing coupled with directional drilling is now commonplace and the USGS has completed many unconventional energy resource assessments of actively producing formations, such as the Marcellus Shale and Bakken Shale, as well as frontier areas such as Alaska, that are only just now exploring for shale oil or shale gas. Assessments are important not only to help predict the amount of oil and gas that might be available in the future but also to allow land and resource managers to plan and prepare for potential future oil and gas development in a prudent and careful manner.

Natural Hazards

USGS has conducted research that associates deepwell fluid injection, a process sometimes used to dispose of produced waters or flowback waters from hydraulic fracturing and gas production, with the triggering of earthquakes. Earthquakes may occur when the injected fluid reaches a critically stressed fault. Deepwell fluid injection is a technique in which wastewater, typically produced waters from the petroleum formation and flowback from the fracking operation, is injected back into the Earth for storage. USGS is researching the factors that control the generation of injection-induced earthquakes, and maintains a series of FAQs regarding the potential earthquake hazards associated with deepwell fluid injection.

USGS has studied recent earthquake swarms in Oklahoma in particular. USGS and partners are tracking and studying a remarkable increase in earthquakes that deepwell fluid injection likely contributes to. In addition, USGS observed a triggered magnitude 5.0 earthquake near Prague, OK, in November 2011 that may have triggered the larger M5.7 earthquake less than a day later. This research suggests that the M5.7 quake was the largest human-caused earthquake associated with wastewater injection.

Hydraulic Fracturing Image Gallery

Useful Links

Recent USGS Energy Assessments for Undiscovered Resources Enabled by Hydraulic Fracturing Include:

See all USGS energy assessments
USGS Energy on Twitter
USGS Newsroom search results for hydraulic fracturing

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