Hydraulic fracturing is a process in which fractures in rocks below the earth's surface are opened and widened by injecting chemicals and liquids at high pressure: used especially to extract natural gas or oil.
How the process works:
The process includes steps to protect water supplies. To ensure that neither the fluid that will eventually be pumped through the well, nor the oil or gas that will eventually be collected, enters the water supply, steel surface or intermediate casings are inserted into the well to depths of between 1,000 and 4,000 feet. The space between these casing “strings” and the drilled hole (wellbore), called the annulus, is filled with cement. Once the cement has set, then the drilling continues from the bottom of the surface or intermediate cemented steel casing to the next depth. This process is repeated, using smaller steel casing each time, until the oil and gas-bearing reservoir is reached (generally 6,000 to 10,000 ft). (FracFocus, 2012) A Duke University study published in 2011 examined methane in groundwater in Pennsylvania and New York states overlying the Marcellus Shale and the Utica Shale. It determined that groundwater tended to contain much higher concentrations of methane near fracking wells, with potential explosion hazard. They also found that the type of gas detected in the water was the same type of gas that was being extracted from the ground. (Clayton, 2011)
FracFocus. (2012, June 20). Fracfocus.org. Retrieved from http://fracfocus.org/hydraulic-fracturing-how-it-works/hydraulic-fracturing-process Clayton, M. C. (2011, May 9). Csmonitor. Retrieved from http://www.csmonitor.com/Environment/2011/0509/Fracking-for-natural-gas-is-polluting-ground-water-study-concludes
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