Shale and tight gas fields involve the industrialisation of entire landscapes with numerous densely spaced wells. Typical gasfields contain thousands of wells. Gasfields also require vast networks of access roads, gas pipelines, compressor stations, processing plants, wastewater holding dams and treatment plants.
Shale and Tight Gas Fracking
Families now living in the Tara gasfields in Queensland report that when CSG was proposed for their area, gas company public relations spokespeople claimed that CSG was much safer than fracking for shale gas. They were assured that fracking for CSG was nothing like the US experience where fracking is for shale gas, because coal seams are closer to the surface than shale deposits. Now, in Tasmania which is only prospective for shale and tight gas, proponents of the gas industry assert that fracking for shale and tight gas is much safer than CSG because shale and tight gas deposits are found in much deeper rock layers.
Shale is Riskier than CSG
Shale gas extraction is not safer than CSG. Fracking for shale and tight gas have their own set of unsolved problems that CSG does not have. The risks of shale and CSG are different, but shale is arguably worse.
CSG is closer to the surface, which provides greater opportunity for contamination of shallower aquifers. However the drilling activity for shale and tight gas still occurs at the surface so at a minimum the same opportunities for air pollution, chemical spills, well blowouts and other industrial accidents that lead to 'contamination events' are present. That said, shale gas fracking involves far higher pressure well injections and uses far more water and chemicals than CSG.
Massive Water Usage
Every shale gas frack requires huge quantities of water. Accepted estimates range from between 11 and 34 million litres of water per shale gas frack, compared to between 2 and 3 million litres per CSG frack. There is no indication of how the problem of water availability for an extremely water-intensive industry would be managed on an island with fully allocated, finite water resources would be solved. MRT has acknowledged that Tasmania's water scheme would be raided by fracking companies.
Shale and tight gas reservoirs contain little water, compared to CSG. This means that when shale and tight gas reservoirs are dewatered, there's very little water that can be recycled for high volume, high pressure well injection and fracking. Immense amounts of water, hundreds of truckloads, has to be trucked in from other sources, such as from surface pipelines or underground aquifers.
Massive Quantities of Chemicals
Every shale gas frack uses 30-80 tonnes of industrial chemicals. In comparison, a CSG frack uses around 11-15 tonnes. In addition to the chemicals regularly used in other fracking operations, tight gas always requires acidation to achieve commercial flow rates. Acidation is the practice of pumping acids into tight gas formations to dissolve the cements between rock grains. Techniques to map out tight gas deposits include exploding dynamite and vibroseis (measuring the vibrations produced with seismic equipment).
Extreme High Pressure Injection
Fracking for shale gas involves far higher pressures than for CSG. Massive volumes of fresh water, mixed with a toxic blend of chemicals and sand (or other 'proppants' such as ceramic beads), are injected into the well under extremely high pressure. The immense pressure causes the rock thousands of metres underground to fracture, stimulating the flow of trapped gas.
Well Casing Failures
Because fracking for shale gas involves far higher pressures than CSG, the risk of well casing failure increases. Shale well casings are like gaskets. If the gasket fails, chemicals, flowback water and gas can be forced up at extremely high pressures, increasing the risk of leaks, blowouts and surface contamination. CSG does not have these extreme pressures.
Anthony Ingraffea on Lethal Gas/Oil Wells
Multiple Wells, Multiple Fracks
Not all CSG wells are fracked, but every shale gas well is fracked multiple times. Each frack injects vast quantities of fracking fluids and muds down the well shaft under immense pressure. Each frack increases the risk of well casings failing.
Land Surface Impact
The industry claims that the surface footprint for shale gas extraction is much smaller than for CSG. The actual experience is of high density well spacing. Fields start with fewer wells, but as the gas depletes, infill drilling radically increases the concentration of wells. The Barnett Shale in Texas has up to 6 wells per square kilometre in some areas.
Slickwater fracturing, the technology we know as fracking today, has been in commercial use for less than 20 years – not the 60 years the industry claims. Because of shale's low permeability, advances in technology were necessary before large scale onshore shale gas deposits could be fracked commercially. It wasn't until 1997, when the technique known as slickwater fracturing was applied to the Barnett Shale in Texas, that shale gas extraction became economical.
It's true that fracking has been used in conventional oil and gas wells for decades, but fracking for shale gas is a very different practice to the technique used to recover oil from depleted oilfields. Oilfield fracking involves only vertical wells, lower pressures, and fewer chemicals. Comparing vertical, conventional fracking with the much greater risks and technical challenges presented by horizontal drilling for shale and tight gas is disingenuous.
In Tasmania, we may not hear much about BTEX (benzene, toluene, ethylbenzene and xylenes) because the use of BTEX as additives throughout the fracking process is banned in Australia. However, BTEX and other naturally occurring radioactive materials (NORM) are naturally present in our geology. Even though BTEX is banned as an additive here, it is mobilised during fracking and brought to the surface in flow-back water.
Shale and tight gas reservoirs are roughly between 2000 and 4000 metres underground, although these depths can vary. Typical CSG deposits are much closer to the surface, usually at depths ranging from 300 to 500 metres. Because of the greater drilling depths required to reach shale and tight gas, workers' exposure to NORM is a much higher risk with shale gas drilling, to the extent that some jurisdictions require their employees to be certified in the handling of radioactive materials.