Hydraulic fracturing, often called fracking, fracing[a] or hydrofracking, is the process of initiating and subsequently propagating a fracture in a rock layer, employing the pressure of a fluid as the source of energy.[1] The fracturing, known as a frack job (or frac job),[2][3] is done from a wellbore drilled into reservoir rock formations, in order to increase the extraction and ultimate recover
y rates of oil and natural gas. Hydraulic fractures may be natural or man-made and are extended by internal fluid pressure which opens the fracture and causes it to extend through the rock. Natural hydraulic fractures include volcanic dikes, sills and fracturing by ice as in frost weathering. Man-made fluid-driven fractures are formed at depth in a borehole and extend into targeted formations. The fracture width is typically maintained after the injection by introducing a proppant into the injected fluid. Proppant is a material, such as grains of sand, ceramic, or other particulates, that prevent the fractures from closing when the injection is stopped. Considerable controversy surrounds the current implementation of hydraulic fracturing technology in the United States. Environmental safety and health concerns have emerged and are being debated at the state and national levels.[4]
http://en.wikipedia.org/wiki/Hydraulic_fracturing
