What actually is Fracking?
Essentially, hydraulic fracturing (or fracking as it is more commonly known) is the recovery of natural gas from shale formations situated deep underground, usually at depths of 2-3 km. Fracking has only come to the forefront of the energy race due to recent developments in horizontal drilling practices that have led to the economically viable recovery of shale gas.
Shale formations are composed of the fossilferous remains of ancient microorganisms and fine grained clay sediments that have settled from suspension in ancient, low energy waters. When the sediment is buried and compacted thermogenic degradation takes place. If the specific temperature and pressure parameters of the 'thermogenic window' are satisfied, the organic carbon content can be turned into methane gas.
Unlike the usual recovery of natural gas from porous resevoir rocks such as sandstones, the very low permeability of the shale ensures the methane remains trapped in tiny pore spaces in situ. The shale formation acts as the source rock, the resevoir rock and the trap rock.
The very high pressures of the injected fluid causes local shale to fracture, releasing the trapped methane. The fissures created in this process allow the natural gas to migrate into the well and then be tapped and stored as a valuable energy source.
Here are some cool links to provide you with the basics on fracking-
http://www.bbc.co.uk/news/uk-14432401
http://www.youtube.com/watch?v=lB3FOJjpy7s
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