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.
Mar 22, 2012
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:
Helmuth found the average distance between the aquifers to vary from zero to hundreds of metres. The Condamine Alluvium, from which several hundred irrigators draw water, is known to be connected with the Walloon Coal Measures. John Hillier found that such interconnectivity exists but research is needed to establish the extent. The relationship is easily seen in this schematic diagram created by the University of Southern Queensland in a grant submission. It’s available as part of Item 3 of Additional Information Received on the Senate committee submissions page.
It appears obvious to the lay person that there is a risk of the sweet-water draining into the coal seam if water is removed from the latter, even without fracking. Yet the industry intended to mine the area.
The government says it’s basically OK apart from a few localised problems with bores, and if not there are always the “make good” provisions.
The Queensland government has specified particular restitution measures but as Dalby lawyer Peter Shannon said at the hearings, the law only requires that an agreement be reached, not the nature of the agreement, and that CSG as the cause had first to be accepted by companies that are perhaps otherwise incentivised. This is not straightforward when there has been over-allocation and a drought. Indeed when two bores failed near Chinchilla, those reasons were suggested as likely by the company and the Queensland government (see Kate Lloyd’s Senate submission, No.270). As of time of writing the issue is mired in data collection and analysis that will go on for over a year after the problem was raised.
A short account of the Lloyd family story is available here.
CSG companies are obliged now to gather baseline data on bores, but the problem is that a snapshot of a dynamic system has limited meaning. If the company is not co-operative, the onus to prove harm lies with the landholder. There is widespread scepticism, picked up by the Senate inquiry, about the efficacy of make good provisions.
Ultimately, landholders are concerned that if the aquifer has been damaged to the extent that the existing bore cannot be made to work and sinking a new bore is unsuccessful, there is no “alternative water supply” for the company to replace the water source. Underground aquifers are fully allocated. No additional surface water can be harvested within the Murray-Darling Basin.
Finally, there is no independent assessment as to whether a company has met it make good obligations.
One of the Queensland government’s preferred options of dealing with the salty brine produced in extracting CSG is to clean it up through reverse osmosis and inject it into a local aquifer. Injection involves an industrial process illustrated here. While this would seem to benefit the long-term availability of water to farms and towns, large quantities will be forcibly injected at a limited number of points, altering relative pressures in the aquifers. It is simply unknown what the long-term effects will be.
Landholders are also concerned about fracking. The geology in Australia is different to that of the shale gas fields of North America, so their experience is not directly transferable. There has been relatively little experience here where fracking is just ramping up.
Many think the Queensland government completely underestimated the problems with the CSG industry and is now playing “catch up” with its adaptive management strategy. The Senate inquiry (Recommendation 1) suggested that it be thoroughly reviewed. Geoff Edwards’ paper cited above actually advised the government in 2006 that there was
“no general pathway for overcoming these challenges … either at a local scale or at a Basin-wide scale. In other words, there is no satisfactory technical or economically viable general solution.”
Nevertheless, Edwards found that the precautionary principle (see Robert Merkel’s excellent article) was not an absolute impediment and the best solutions would be project-specific, supported by changes in legislation, regulation and other measures.
Such measures now implemented include funding an information service through Agforce, mediation services based in Dalby, the establishment of the Surat Basin engagement committee to bring together representative landholders with miners and the government, a land access review, a coal seam gas water feasibility study, various codes of practice, a compliance and enforcement function and a very neat website.
Yet to this outsider it seems evident that genuine and significant perceived risk remains, one that needs to be met with science or recognised, quantified and dealt with through satisfactory policy responses.
Agforce estimated that the CSG industry would take away about $2 billion in value from farmland in southern Queensland.
Further knowledge gained through science is needed. The recent establishment by the Commonwealth of an interim independent expert scientific committee with $150 million to investigate problems associated with gas and large coal mining projects including the assessment of water resources is recognition of that need. Yet such knowledge will not, if the contentions identified by Polglase and Bridle above are valid, provide the necessary certainty at a farm level.
Unless these contentions are shown to be invalid a burden of risk remains at the individual farm level, now and into the future.
The Senate inquiry report (Recommendation 16) sought to collectivise this risk by suggesting an “independently managed trust funded by the gas companies to make financial provision for long-term rectification of problems”. If this suggestion is not accepted consideration should be given to a risk premium paid to individual landholders up front. Bankers would understand such an approach.