Hydraulic fracturing is used in oil and natural gas production. After a well is drilled into reservoir rock that contains oil, natural gas, and water, every effort is made to maximize the production of oil and gas. In hydraulic fracturing, a fluid (usually water containing specialty high-viscosity fluid additives) is injected under high pressure. The pressure exceeds the rock strength and the fluid opens or enlarges fractures in the rock. These larger, man-made fractures start at the injection well and extend as much as several hundred feet into the reservoir rock. After the formation is fractured, a “propping agent” (usually sand carried by the high-viscosity additives) is pumped into the fractures to keep them from closing when the pumping pressure is released.
Hydraulic fracturing allows the oil or natural gas to move more freely from the rock pores to a production well so that it can be brought to the surface
This technique is used where the oil or gas is trapped inside rocks which are not very porous. Examples are natural gas found in shale, with the best known example being Haynesville Shale& Marcellus Shale, Coalbed Methane, and Oil Shale such as that found in the Bakken Oil Field
The technology has been used since the 1940s in more than 1 million wells in the United States.
This technique has been the subject of much speculation as to its impact on ground water. The only serious government study of the subject however concluded that it poses very little risk.
Based on the information collected and reviewed, EPA has concluded that the injection of hydraulic fracturing fluids into CBM wells poses little or no threat to USDWs and does not justify additional study at this time.
- Hydraulic Fracturing from the EPA
- Hydraulic Fracturing from the API
- The U.S. Environmental Protection Agency Study