Chris Hartcher ... Minister for Resources and Energy. Photo: Dean Osland
FRACKING is more likely to take place during coal seam gas drilling near Sydney than in many other gas fields around Australia, according to an unpublished report from the NSW Chief Scientist that was commissioned by the state government.
In a briefing to the Resources Minister, Chris Hartcher, the Chief Scientist and Engineer, Mary O'Kane, concluded that companies would be likely to start fracking once ''sweet spots'' for gas have dried up.
Fracking is a drilling technique that forces gas to the surface by pumping a mixture of water, sand and chemicals underground. Opponents say it can cause gas leaks at the surface, crack underground aquifers, and pollute water with toxic chemicals, though some experts dispute the degree of damage it can cause.
The documents, obtained by the NSW Greens under freedom-of-information laws, suggest that if large-scale coal seam gas extraction takes place in the Sydney Basin, fracking will probably end up being used because of the geology of the rock strata under Sydney and the age of the coal deposits.
''Coal seams from some basins in NSW appear from the advice to be more likely to need fracturing than others,'' Professor O'Kane wrote in her briefing, referring to coal seams in the Sydney, Gunnedah and Gloucester basins.
''In the later stages of coal seam gas developments after the high permeability coal seams or 'sweet spots' have been drilled, it is more likely that wells will then be [fracked] to increase production.''
However, she added that ''the development of new technologies may significantly reduce the need for hydraulic fracturing in the future''.
AGL has reversed its position on fracking, saying the drilling technique is now back on the table as an option, after earlier ruling it out.
The company plans to drill 66 wells in western Sydney, between Campbelltown and Liverpool. It has promised that there will be no surface impact from drilling, and says it will meet strict health, safety and environmental standards.
The Chief Scientist's advice was based on reviews conducted by three experts - Professor Val Pinczewski, the head of the school of petroleum engineering at the University of NSW, Professor Peter Cook, of the cooperative research centre for greenhouse gas technologies at the University of Melbourne, and Dr Rob Jeffrey, the CSIRO's research program leader in petroleum engineering.
A separate briefing note to the minister, also from the chief scientist, dated November 2011, was critical of a separate series of consultants' reports commissioned by the government into coal seam gas drilling standards.
The NSW Greens said the documents showed fracking was inevitable under Sydney, if the AGL project was approved.
''Our aquifers and geological formations are like Humpty Dumpty, once you've fracked it, you can't put it back together again,'' the Greens MP Jeremy Buckingham said. ''Barry O'Farrell should act now to protect land and water rather than leaving it to a future government to say sorry for the damage done by fracking for coal seam gas.''
The AGL proposal for western Sydney will be on public exhibition until February 8.