Fracking is short for hydraulic fracturing, the process of fracturing rock. Although this process has been used for decades, more recently it has been used to specifically refer to the fracturing processes involved in the extraction of gas and oil trapped in sedimentary rock such shale.
What is shale?
Shale is a sedimentary rock formed by the compression of clay and silt particles at the bottom of a lake or sea. As other geological materials formed on top of the layers of shale the pressure caused the shale to compress. Shale has a flaky composition breaking into thin parallel layers.
Along with the clay and silt that make up shale it also contains organic matter. Over time this organic matter decomposed and, due to the pressure from the layers above, formed hydrocarbons. Hydrocarbons are the basis of fossil fuels.
The process of extracting this trapped oil or gas in the shale involves drilling a large shaft is drilled hundreds of meters into the Earth, when the drill reaches the layer of shale a horizontal shaft is drilled into the shale layer.
Fracking fluid is then pumped into the shaft, this fluid is made up of water, sand and chemicals. The fluid is pumped in as such high pressure that it produces millions of small cracks in the rock, the sand in the fracking fluid prevents the cracks from closing up and the chemicals do jobs such as killing bacteria.
The fracking fluid is then pumped out and the gas can then be extracted.
Recently there have been concerns around the environmental and health effects of fracking for hydrocarbons. One of the main issues is the contamination of underground water sources, the drilled shafts could pass through wells or the gas could penetrate them. The chemicals used in the fracking fluid or the shale gas itself could have serious effects on the water quality of an area, though the chemicals used vary significantly depending on the local geology and are often only used to protect the mechanical operations.
Other issues around fracking are the vast volumes of water necessary and the process causing small earth tremors. Another concern with fracking is that it is still relying on fossil fuels, the shale gas extracted will still form carbon dioxide when formed and there is concern that the process distracts from the search for more renewable energy sources.
Fracking in Ireland
Currently the process of fracking is not legal in Ireland however, studies have being carried out by the EPA into how fracking process could be best monitored if it were to take place. The area known as the Northwest Ireland Carboniferous Basin has been identified as a shale rich area, this comprises parts of Fermanagh, Cavan, Sligo, Leitrim, Donegal and Roscommon.
Although fracking may support short term transition to renewable energy, it does not address the longer term issue of global warming. It is vital that we continue to search for renewable resources to meet our energy needs. One method in which we can harness the Earth as a source of energy is Geothermal energy.