By ERWIN CHLANDA
Risks of fracking of shale for gas and oil can be reduced by careful study of the geological layers above, and by avoiding the controversial process if these layers are prone to allow contamination of high-quality ground water.
This is the view of Dr Eric Roberts from the science department of the James Cook University in Townsville.
Shale fracking, such as it is now proposed to be done on a broad scale in the NT, has been in use for around half a century in the US, he says.
It usually takes place at a far greater depth than coal seam fracking which is much nearer to good water because it is done closer to the surface.
The water at the depth where shale fracking usually takes place is brackish and of a lower quality.
Dr Roberts says the key to reduce the risk of contamination – it can never be ruled out – is knowledge of the nature of the rocks between the fracking site and high quality aquifers – usually above.
Establishing the permeability and porosity of these layers would preferably be done by independent studies, not by the mining companies.
The fracking of shale is usually less risky because it is not porous; the gas or oil is contained in it because it could not get out until fracking took place.
“The deeper the targets, the less likely it is that you get seepage and contamination of ground water,” says Dr Richards.
“Although the risk of groundwater contamination is not necessarily high, it would be short sighted to start fracking without homework.
“Really good geological characterisation is necessary.”
He says public concern about fracking in the US grew when it became more wide-spread. There is a tendency to over-react, but regulation needs to be considered.
Another source told the Alice Springs News Online that shale fracking is not only deeper, it also requires fewer wells drilled from the surface as modern technology allows horizontal drilling in all directions under ground.
IMAGES: Top – shale gas rig. Below – Source: Ground Water Protection Council, Exxon Mobile, Austin Exploration Limited.
By ERWIN CHLANDA