Federal

Mar 22, 2012

Behind the Seams: going underground to examine CSG risk to aquifers

FAQ Research writer Brian Bahnisch looks at the issues thrown up in relation to underground aquifers and cola seam gas.

In CSG and the land: straight from the farmers’ mouths, I looked at some of the impacts of CSG mining on farming activities above the ground. Here, I examine the issues thrown up in relation to underground aquifers. Professor Roger Jones in his article on risk tells us:
Coal seam gas issue presents a wicked problem. Wicked problems are hard to define, have competing values and cannot be definitively solved. For wicked risks, perceptions are just as important as the risks themselves.
He identifies three areas of risk: calculated risk, perceived risk and political risk. In this article I am concerned with the first two in relation to coal seam gas, underground aquifers and farming. Calculated risk is determined by experts, not just by science but also values, according to Jones. Based on their understanding of calculated risk, the various parties will have a perception of risk that determines their behaviour. That is, while perceived risk has a significant emotional dimension, which is inevitable and must be acknowledged, it is also informed by an understanding of calculated risk. The interim Senate inquiry report (hereafter Senate report) in chapter two quite comprehensively surveyed the calculated risk of CSG activity to underground aquifers, acknowledged the understandings and perceptions of landholders, and came to the conclusion that:
in view of the levels of uncertainty acknowledged by professional bodies and industry, the production approvals for the initial projects in Queensland were given prematurely.
The Senate committee felt that the uncertainties were such that no further production approvals should be given pending the completion of the Queensland Water Commission’s Surat Basin groundwater model and the CSIRO and Geoscience Australia basin scale investigations of water resources (Recommendation 3, para 2.58). However, a serious question has been raised as to whether risk can in fact be reduced to acceptable levels at a farm level. At the same time, the die is cast, the approved investments are so large that the possibility of buying out the whole industry simply does not exist. We have to make the best of it, but we may indeed have a wicked problem that "cannot be definitively solved". In the Surat Basin and in the Murray-Darling Basin generally widespread use is made of underground aquifers in farming, industry and for human consumption on farms and in towns. We are told that 22 of 23 towns in the gas areas on the Western Darling Downs get 100% of their water from aquifers. Failure of aquifers can ruin the business of irrigators, feedlot operators and other producers, so the stakes are high. Let’s have a closer look at this "wicked" problem. We are perhaps all familiar with the cutaway images such as the one on the ABC CSG site of neat sedimentary layers like a sponge cake, which clearly distinguish, for example, the coal seams and the aquifers of the Great Artesian Basin (GAB). Hydrogeologist John Polglase here and here tells us that these diagrams are drawn to show simple concepts, and are not a reflection of the reality beneath our feet. What we have today is the result of physical and chemical processes over many millions of years, with much lifting, folding, faulting and interpenetration of major geological systems. Interestingly, the Senate report (para 2.11) tells us that the GAB was formed from sediments deposited  65 million to 250 million years ago. This site tells us that the Surat Basin coal deposits were formed through six sedimentary cycles over the Jurassic/Cretaceous periods, roughly the same time frame. What we have is a complex dynamic rock/fluid/gas system which is always changing. Polglase describes it thus:
Below ground, water and gas are constantly moving through fractures and fissures in the sedimentary rocks, at various rates under varying pressures. The rocks are also moving -- continuously or abruptly -- as nature balances and rebalances the stresses and strains according to the laws of physics. Alongside this physical balancing act, there is also chemical balancing between the solids in solution, precipitants from solution, and changes in acidity, salinity, temperature, oxygenation. Any extraction and redistribution of mass: solid (coal, ore, inter- over-burden), water or gas, creates voids which in turn cause nature to attempt a new equilibrium by re-balancing the physical and chemical states of the fluids and rocks.
So if we extract large volumes of groundwater there will be changes to the mass, stress and chemical balances of the system. The question is how much, and whether sourcing water from potable aquifers that lie above and below the coal seams will be jeopardised. Polglase has emphasised the micro fracturing of rock formations over the millennia.Geoff Edwards, in a paper cited in the Senate report, states that it is common to find cases in the alluvial aquifers of the Murray-Darling Basin where depressurisation in a good aquifer can induce flows of very salty water into the good aquifer from or through overlying clay aquitards which would normally have been considered relatively impermeable (Edwards, G. Is There a Drop to Drink? An issues paper on the management of water co-produced with coal seam gas. Queensland, Department of Mines and Energy, 2006). Groundwater, he says, can be induced to flow over a distance greatly separated from the local extraction. And this:
No one can realistically know in advance what will happen, and what hydraulic connections with other aquifers will appear once the coal seams are dewatered.
This is the challenge for the experts and government policy makers. Anne Bridle, now vice-chair of the Basin Sustainability Alliance, in writing her personal submission to the Senate inquiry (downloadable from the BSA site) says she consulted independent groundwater hydrologists. She writes:
Seismic reflection data used in the CSG industry to infer strata formation properties is subjective and does not provide detail. It can only pick out the major faults and fissures in geological strata. It is unable to determine the location of geological flaws, fissures, faults, joints and planes of weaknesses, load and relaxation cracks -- all which may be groundwater (with methane) highways and superhighways. They also may become highways through mass load changes as water at depth is removed rapidly from the system. Groundwater (with methane) may not be constrained to a particular stratum or horizon (eg. seepage, springs, hidden faults etc.)
In other words, the basin-wide mapping such as that being undertaken by the Queensland Water Commission, Geoscience Australia and the CSIRO cannot give certainty at an individual farm level to landholders or their bankers. Moreover, professor Stephen Raine’s examination of the modelling of CSG companies suggests that the significant effects may not appear until 2050 to 2060. In the Senate report Senator Heffernan repeatedly referred to advice from the CSIRO, which told the committee that the relationship of aquifers was unknown and that to repair any significant damage naturally could take 250 years. To make this statement in itself implies that they think such damage can occur. In 2008 Mal Helmuth undertook a preliminary assessment of risk to Queensland aquifers from CSG activity. The projected production of water from coal seams is quite large, projected to be several times the domestic usage. Potentially, Helmuth says (p.33), the loss of water from the GAB aquifers could be of the same order as current groundwater use. While Helmuth does an excellent job in identifying the parameters and scoping the issues, the results are limited through lack of data. No contoured map of risk was possible. He was only able to identify "point" risk, where sufficient data was available. From this it was evident that risks were higher within the Surat Basin than elsewhere. The highest risks were to the Hutton, Springbok and Condamine Alluvium aquifers. Helmuth found that the risk points were spatially heterogeneous, that is higher, medium and lower risk points were clustered together. The biggest limitation of the study is that only relative risk could be discerned. There was no sense at all what high and low actually meant. Recalling Bridle’s statement above, individual farms lie at Helmuth’s "points". When a well is drilled, information about the geology is gathered. However, no certain information can be gained about the existence of "geological flaws, fissures, faults, joints and planes of weaknesses, load and relaxation cracks" between the wells. Helmuth gives this helpful diagram to illustrate the relationship of the aquifers and the possible effects of dewatering:

This image shows the hypothesised risk to other overlying aquifers:

Free Trial

You've hit members-only content.

Sign up for a FREE 21-day trial to keep reading and get the best of Crikey straight to your inbox

By starting a free trial, you agree to accept Crikey’s terms and conditions

7 comments

Leave a comment

7 thoughts on “Behind the Seams: going underground to examine CSG risk to aquifers

  1. Stickey

    I hear the drillers and miners in the Cooper Basin have been “fraccing” over the past 20 years. The GAD water still seems to be just as hot and potable for stock anyway.

  2. Mal White

    @STICKEY

    You make a valid point.

    The environmental implications of CSG extraction is a very complex. CSG extraction is not new to Australia so it seems obvious that a study of what has happened so far should have rated at least a mention in this article.

    All the talk on “wicked risks” seems a bit of an unnecessary and bizarre play on words.

    On one hand I respect the points made about the uncertainty of dealing with such complex and variable geology. Each CSG well is going to have its own unique set of risks. Time will tell whether the industry can be successful without major damage to the environment.

  3. Damotron

    At some point there will be a class action against the mining companies worth millions and millions of dollars. Bet the tax players end up playing the bill as the miners jump ship. In Queensland the P in LNP stands for Palmer.

  4. Brian Bahnisch

    Stickey I don’t agree with Mal White that your comment is valid. If you followed the link to the work by Mal Hellmuth you would note that the Surat Basin carries more risk than the Bowen Basin. As I recall the Cooper Basin wasn’t mentioned. The point is that you can’t extrapolate from the experience in one basin to another. Also some areas within the basin carry more risk than others.

    Also the incidence of fracking in the past is a mere fraction of what is going to happen in the future.

    Third, fracking tends to be concentrated in particular areas. The Dalby hearings of the Senate Committee were told about an area where 1700 out of 2000 wells were going to be fracked.

    We had intended to do a separate piece on fracking. because of that and space considerations I didn’t go into it in any detail.

  5. Brian Bahnisch

    Mal White, further to what I said to Stickey, the Senate Committee found that the more wells we drilled the more we would know about the geology of the areas we are drilling, and the risks entailed. But we would learn through the experience itself. But in doing so we create the risk.

    They call it a Catch 22. The Queensland government calls it adaptive management. But it’s a wicked problem in that the risks cannot be fully assessed before the holes are drilled.

    A major point of the whole piece was that no matter how much research you do you can’t eliminate the risk at the farm level, or indeed from one hole to another, or be sure that the problems won’t appear in years to come. It’s a wicked problem in the terms specified by Professor Roger Jones. The study of risk is his speciality.

    This is not a trivial play on words.

  6. Brian Bahnisch

    The comments thread at Larvatus Prodeo where this post was also published is now closed, but over there Dale Stiller posted a link to Ben Kele at CQU on the treatment of ‘associated water’, the salty water co-produced with the gas.

    They are trickling the water over natural volcano rock which removes the sodium chloride and then they add calcium and magnesium salts to promote soil health and plant health in a process that is cheaper and less energy intensive than reverse osmosis.

    That’s all fine and good, but he makes the statement that demineralised water from the reverse osmosis process is actually harmful to the soil. In fact he implies it is just as harmful as sodium chloride.

    I’d actually like to hear what a soil scientist says about this issue.

  7. Brian Bahnisch

    Further to my last comment, I’ve consulted two agricultural scientists. It seems that demineralised water is not harmful to plant life as such. Obviously it’s preferable if the water contains minerals that promote plant growth.

    The same would apply to soil.

    This is a separate issue from disposing of the cleaned-up water by releasing it into creeks and rivers. There it creates unnatural flows and the water is cleaner than the stream ecologies are used to.

Share this article with a friend

Just fill out the fields below and we'll send your friend a link to this article along with a message from you.

Your details

Your friend's details

Sending...