What is Fracking?
Hydraulic fracturing (fracking) is a technique that allows for the exploitation of methane gas from unconventional sources. Unconventional sources are rock layers deep underground in which the gas does not occur in a large bubble, but is dispersed in very small pore spaces and fractures throughout the rock. To release it, the rock needs to be cracked, in a process called hydraulic fracturing or fracking. The main targets for this process are coal bed methane (in layers of coal), tight gas (in sandstone) and shale gas (in shale or mud rock).
To enable this process, drilling pads with 8-16 wells are constructed. To reach the rock layer, first a vertical well is drilled. The drilling then continues horizontally, generally for about one-and-a-half kilometers through the rock layer. The wellbore is lined with concrete, in which small holes are drilled. The rock is then cracked by explosions using a perforating gun.
Fracking fluid is pumped into the well under high pressure to enlarge the cracks in the rock and release the gas or oil. Once the well is depressurized, 40% to 60% of the fracking fluid is forced back up the pipe. After that, the gas freely flows to the surface and is captured. It is then treated (if necessary) and transported via tankers or pipelines to be sold.