The Ground Water Protection Council wrote in their article "What Is Hydraulic Fracturing?" on FracFocus, a hydraulic fracturing chemical disclosure registry website (accessed Nov. 4, 2011):
"Hydraulic fracturing, commonly referred to as fracking, is the process of creating small cracks, or fractures, in underground geological formations to allow natural gas to flow into the wellbore [the drilled hole] and on to the surface where the gas is collected and prepared for sale to a wide variety of consumers.
During the fracking process, a mixture of water, sand and other chemical additives designed to protect the integrity of the geological formation and enhance production is pumped under high pressure into the shale formation to create small fractures.
The newly created fractures are 'propped' open by the sand, which allows the natural gas to flow into the wellbore where it is collected at the surface and subsequently delivered to a wide range group of consumers."
ProPublica, a non-profit investigative journalism organization, wrote on its webpage "What Is Hydraulic Fracturing?" on ProPublica.org (accessed Nov. 28, 2011):
"Hydraulic fracturing, or 'fracking,' involves the injection of more than a million gallons of water, sand and chemicals at high pressure down and across into horizontally drilled wells as far as 10,000 feet below the surface. The pressurized mixture causes the rock layer... to crack. These fissures are held open by the sand particles so that natural gas from the shale can flow up the well."
EARTHWORKS, an environmental advocacy organization, wrote in its webpage "Hydraulic Fracturing 101" on earthworksaction.org (accessed Nov. 4, 2011):
"Often an oil- or gas-bearing formation may contain large quantities of oil or gas, but have a poor flow rate due to low permeability, or from damage or clogging of the formation during drilling. This is particularly true for tight sands, oil shales and coalbed methane. Hydraulic fracturing is a technique used to create fractures that extend from the well bore into rock or coal formations. These fractures allow the oil or gas to travel more easily from the rock pores, where the oil or gas is trapped, to the production well. Typically, in order to create fractures a mixture of water, proppants (sand or ceramic beads) and chemicals is pumped into the rock or coal formation.
Eventually, the formation will not be able to absorb the fluid as quickly as it is being injected. At this point, the pressure created causes the formation to crack or fracture. The fractures are held open by the proppants, and the oil or gas is then able to flow through the fractures to the well."
The US Department of Energy (DOE) wrote in its Nov. 3, 2011 publication "Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources" at water.epa.gov:
"Hydraulic fracturing is a well stimulation technique used to maximize production of oil and natural gas in unconventional reservoirs, such as shale, coalbeds, and tight sands. During hydraulic fracturing, specially engineered fluids containing chemical additives and proppant [sand, ceramic, or other particulates] are pumped under high pressure into the well to create and hold open fractures in the formation. These fractures increase the exposed surface area of the rock in the formation and, in turn, stimulate the flow of natural gas or oil to the wellbore."