Gas wells are often drilled through or near aquifers, and complaints about polluted well water are not uncommon. One frequently expressed fear, especially in areas where fracking is new, is that the fracturing of rock underground will allow contaminated liquids and liberated shale gas to migrate upward from the shale deposit and into the water table. Industry officials insist, and most environmental officials agree, that this is extremely unlikely. A typical frack job is done at depths of 1,500 to 2,500 meters (5,000 to 8,000 feet). Between the shale deposit and the floor of an aquifer (which is normally found no more than a few hundred meters below the surface) are numerous layers of rock that would prevent the infiltration of gas and liquid-though some scientists believe there is a chance, in some geologic formations, that liberated shale gas may be able to follow existing faults and fractures upward to the water table. A more likely scenario suggested by some scientists might be the diffusion of shale gas through old, disused wells that have not been adequately cased or plugged. One frequently documented cause of local Föroreningar är defekt hölje i den del av en aktiv gasbrunn som passerar genom en akvifer, vilket gör att produktiongas och vätskor kan passera in i vattenförsörjningen .
In 2010 Gasland, an American documentary film critical of fracking, created a sensation with its footage of a kitchen faucet spewing flames in Fort Lupton, Colorado. The success of the film (which was nominated for an Academy Award) inspired a number of imitation videos on the Internet. Such events might indeed be traceable to drilling, which on many occasions has disturbed previously unknown pockets of gas located close to aquifers, enabling methane gas to permeate well water in concentrations higher than normal. However, such disturbances can be created by drilling of almost any kind, whether for gas, oil, or even well water. For this reason, industry officials, while conceding that drilling procedures should be held to strict standards, nevertheless insist that explosive conditions almost certainly would not be caused directly by the hydraulic Frakturering av skifferavlagringar djupt underjordiska .
