Hydraulic fracturing, put very simply, is the breaking of rocks with fluids. Cracks are made or natural ones increased in solid rock to facilitate access to oil, gas, and water. Hydraulic fracturing (also known as fracing, and popularly ‘fracking’) has been a widely used technique for the last sixty years.
Liquid is pumped into the rock surrounding a well and eventually the pressure becomes so great the rock cracks, making it possible to access the material being extracted. The liquid is either mixed with tiny solid beads (proppants) or these are injected later. The function of proppants is to keep the crack open, otherwise it would seal up again after the liquid stopped being pumped.
The proppants can be sand, ceramic or various artificial materials. They are more permeable than the surrounding rock and so form a channel that liquids or gases can easily move along.
Fracing lets the oil or gas travel from the rock where it is trapped to the well where it is being extracted. It can also allow physical access to solid materials such as coal. In the case the fractures are used to induce cave-ins that will allow mining to occur. Most natural gas requires fracing before it can be extracted economically due to it usually occurring in low permeability materials, which means that it doesn’t move much.
Fracing has been associated with a number of environmental problems. Most of these arise from the fluid being used. The hydraulic fluid is not usually just water. It includes a variety of chemicals, some of which are highly toxic. The proppants are generally harmless but toxins in the hydraulic fluid can cause serious problems. Some of the fluid is usually pumped out afterwards but a significant proportion remains. This can contaminate groundwater, leading to health concerns.
There is also the possibility of air pollution occurring because of the accidental release of natural gas. In certain areas fracing can trigger seismic activity or lead to the ground caving in. Drilling for natural resources does have a large number of risks attached and these have got to be minimised to avoid serious environmental disturbance.
Fracing has been an essential part of many oil and gas works for a long time. It has an arguably even more important use in getting groundwater wells going again. While the practice can’t really be stopped, it is essential that it is done properly and with full regard to safety precautions.
Sources:
http://www.earthworksaction.org/FracingDetails.cfm
http://www.informaworld.com/smpp/content~db=all~content=a926011794~tab=content~order=page
