Fracking, in a nutshell, consists of the following four steps:
1. Vertical drilling commences till a target depth is reached, at which point the drill goes horizontal.
2. A perforating gun blows holes through the walls of the well, creating channels for the fracking fluid (a mixture of water, sand and chemicals) to reach the surrounding shale.
3. The fracking fluid is injected at high pressure to fracture the shale, while the sand in the fluid keeps the cracks open.
4. Part of the fluid flows back to the surface (the amount depends on the depth, horizontal distance and number of times a well is fractured). The natural gas then flows up through the well.
The sand and chemical additives help to eliminate bacteria from the water, lubricate the fracking process and prevent scale deposits that can build up on piping and equipment; they are, therefore, essential to effectively extracting shale gas.
Information taken from:
http://www.fin24.com/Opinion/Columnists/Fracking-in-a-nutshell-20120912
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