Hydraulic fracturing makes it possible to produce oil and natural gas in places where conventional technologies are ineffective. It uses water pressure, under tight controls, to create fractures in rock that allow the oil and natural gas it contains to escape and flow out of a well. Hydraulic fracturing is well-regulated and safe, and it has a proven track record.
In 2004, the U.S. Environmental Protection Agency concluded, “the injection of hydraulic fracturing fluids into coal-bed methane wells pose little or no threat to (underground drinking water).” The agency, in a review of incidents of drinking water well contamination, found “no confirmed cases linked to fracturing fluid injection of CBM (coalbed methane) wells or subsequent underground movement of fracturing fluid.” See EPA's Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing.
On average, 99.5% of the fluids used in hydraulic fracturing are a combination of freshwater and compounds, which are injected into deep shale gas formations and then confined by thousands of feet of rock. For more detailed information, see Energy in Depth's "A Fluid Situation."