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Feeding and healing the world: through regenerative agriculture and permaculture

Posted on 15. January, 2013.

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Let us look a little more closely at fracking for shale gas and shale oil, which has led to a promise of energy independence for the USA, if not the rest of the world.

The process of hydraulic fracturing (called frac’ing in the industry but fracking in the media) has been used since 1947 to fracture impermeable rock so that oil and gas may be recovered from it. A hydraulic fracture is formed by pumping a fracturing fluid into a borehole drilled into the source-rock so that the downhole pressure exceeds that of the fracture gradient of the formation rock. The pressure causes the formation to crack, whereupon the fracturing fluid enters and extends the crack more deeply into the formation. To keep the fracture open once the injection is complete, a solid proppant, commonly sieved round sand, is added to the fracture fluid. The propped hydraulic fracture then becomes a high permeability conduit through which the formation fluids can flow to the well. For the extraction of shale-gas, wells are dug vertically into the ground and then branched off horizontally into the shale, making the gas far more accessible. Natural gas is the cleanest-burning hydrocarbon fuel, and North America has vast reserves which, it is claimed, could replace petroleum products from overseas. The development of techniques for horizontal drilling has made it economical to extract the gas from shale seams that were previously considered to be inaccessible.

Since the fracturing (fracking) fluid contains various toxic materials, there are fears that these may leak out, along with methane, and contaminate aquifers from which drinking water is drawn. However, two studies, one from Duke University and another from the University of Texas found no evidence for any leakage of fracking fluid into the water supply. In respect to methane leaking into the groundwater, there is a video on YouTube showing tap-water so heavily contaminated that it can be ignited. Hence, there is cause for concern, and while the Texas team is of the opinion that fracking is not the cause, the earlier study by Duke University found a build-up of methane in water near fracking drills. There are issues of high natural levels of methane in the groundwater in the Marcellus Basin and inadequate disposal of wastewater from gas-drilling operations. The matter is, therefore, complex and remains to be fully resolved.

Christopher J. Rhodes

doi: 10.3184/003685012X13504990668392


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