Queensland's Citizen Science Hub

Property owners Dave and Liza Balmain (“Glendon”, Nangwee Queensland) have supplied some documents which shed some considerable light on the failure of the Queensland Government to protect the public interest in its management of the coal seam gas industry.

Effect of free gas on water supply

First is a report by Klohn Crippen Berger (KCB) supplied to the CSG Compliance Unit (CSGCU), Department of Natural Resources and Mines on the potential effects of free gas on bore water supply from CSG development in the Surat Basin. Dated 11 March 2016, the report concludes:

“The focus of this review is on the possibility that, if free gas from CSG development does migrate to a water bore than, how it can impact on a bore’s capacity to supply water. The two fundamental questions in this context are:
1. Could there be free gas when there is no decline in water level in that bore from CSG development; and
2. Could the presence of free gas affect the capacity of that bore to supply water?

An assessment of literature and application of scientific principles suggests that conceptually, simple answer to each of these questions is ‘yes’. Free gas from CSG development can occur in water bores that do not experience a water level decline from CSG development. Presence of free gas in a water bore also directly and indirectly affects its capacity to supply water, unless remedial actions are taken.”

Hydraulic connectivity

A fact sheet by Dr Bryce Kelly of the University of New South Wales titled: “Evaluating the extent of hydraulic connectivity focus on between the Condamine Alluvium, the Great Artesian Basin and the Walloon Coal Measures.”

Location of exploration boreholes

In answer to a question on notice in the Parliament, the Minister (for Resources and Critical Minerals) gave a most remarkable answer on 13 June 2024:

“The Department of Resources has identified at least 993 holes drilled within the vicinity of the Condamine Alluvium between 1960 and 1979. This figure is approximate given that the department does not hold a complete dataset containing legacy boreholes drilled, the geological units intercepted, or their precise location. …The department has identified the location of 18 of the 993 boreholes reported.” (Emphasis added).

Neglected exploration holes

On 15 September 2024 the Balmains wrote to the Department of Environment, Science and Innovation “regarding new information that has come to light which escalates concerns about the future integrity of the Condamine Alluvium in the face of expanding CSG development”:

“Dear DESI Underground Water,

In regards to the impacts from coal seam gas extraction on groundwater, which you oversee as per Chapter 3 of the Water Act 2000, could you please advise if the uncapped/unsealed coal exploration holes that were drilled in the 1960s and 1970s across the Condamine Alluvium, are included in the OGIA Condamine Alluvium Groundwater Model.

From a response to a Question on Notice (QON, attached) posed to the Minister for Resources and Critical Minerals by our local Member Pat Weir MP, it is apparent that there are an estimated 993 legacy coal exploration holes that have been drilled through the Condamine Alluvium extent, however the Department of Resources is only aware of the location of just 18 of these holes and is alarmingly clueless as to the condition of all 993 holes.

As per this article by a local, well-respected water driller who has decades of experience drilling in the Condamine Alluvium and Great Artesian Basin, these coal exploration holes are like dormant conduits, waiting to be awoken once the CSG depressurisation commences in the underlying Walloon Coal Measures. The response to the QON adds immense weight and substance to the momentous concerns of this expert water driller, who understands the immense value of the Condamine Alluvium to our region.

As we can see in this diagram from the Underground Water Impact Report (UWIR) 2021, the reversal in hydraulic gradient between the Condamine Alluvium and the Walloon Coal Measures has already commenced in the western margins of the Condamine Alluvium (brown contours), in the vicinity of existing gasfield development.  Wherever these coal exploration holes exist, they are a potential conduit for water loss from the Condamine Alluvium to the depressurised WCMs.

A study by the University of NSW has actually quantified an estimated rate of annual water loss from the Condamine Alluvium to the WCMs via one of these legacy bore holes, once CSG depressurisation were to commence.

As per the attached article, Dr Bryce Kelly and his team concluded:

“If the post-development head in the WCM is 50 metres below the CA (a conservative estimate based on CSG production modelling), then a single leaky well is predicted to transfer 263 ML/a from the CA to the WCM. Our modelling highlights the need to: 1) Investigate the potential impact of partly penetrating wells; 2) locate and remediate leaky abandon wells to prevent the movement of fluids between strata in areas of CSG developments.”

As we can see from the Stratheden gasfield monitoring wells in the above diagram, the 50 metre head difference between the two formations has already been achieved due to CSG extraction.  If such legacy exploration holes exist in this location they could stand to lose over 250ML of good-quality water per year, per hole, from the Alluvium to the underlying Walloons.

These legacy exploration holes also wait to act as conduits to gas migration (free gas) from the depressurised Walloons, where methane risks entering overlying good-quality aquifers such as the Condamine Alluvium, as well as escaping to the surface as gas seeps, enhancing global warming greenhouse gas emissions.

As per the attached report Potential effects of free gas on bore water supply from CSG development by Klohn Clippen Berger (2016), written by none other than Sanjeev Pandey, the force of buoyancy will overtake the intended mobilisation of gas via the pressure gradient to the well head at a certain distance from the depressurisation zone (gas well) and travel to points of low pressure; whether that be legacy coal exploration holes, water bores, existing geological contact, faults/fractures, or gas wells with corrosion integrity issues (of which there are countless).

As explained in the KCB report:

It is clear from this report, that free gas (methane) has the high potential to migrate upwards, via the force of buoyancy, within a staggering 10-15km range from the depressurisation zone (gas well).

This risks affecting large swaths of the Condamine Alluvium, especially where pathways exist and particularly in a geological up-dip direction from the gas well/gasfield.

The town of Dalby comes to mind.  With a population of over 13,000 people which relies predominantly on the Condamine Alluvium for its town water supply, it stands to be at great risk from the impacts of expanding CSG development.

As clearly outlined in the KCB report, the ingress of methane in the Condamine Alluvium would be a devastating game-changer for so many regional residents who rely on this invaluable water resource, whether that be for residential use, water for stock purposes, or for the irrigation of food and fibre crops.

The impacts from methane in our ground water supplies would detrimentally affect our bores’ capacity to supply water, due to the following causes:

  • Free gas hampers pumping operations and damages pumps and infrastructure, potentially resulting in costly operations and replacements. Damages occur through gas locks, cavitation, overheating and blow-outs. 
  • Free gas in the formation around a water bore provides a resistance to flow of water (i.e. reduces the water permeability) to the bore and reduces bore’s designed capacity or bore yield.
  • Free gas affects water quality in bores by creating turbid water and sediment movement resulting in coloured, slimy and smelly water.  It can also potentially lead to the conversion of dissolved sulfate into odoriferous, noxious and toxic sulfides.  Hydrogen sulfide can lead to problems of odour, toxicity and corrosion of casings and pipe.
  • Free gas contains methane which can burn and can be explosive – posing a significant safety threat.  This can pose difficulties in running and maintenance of a bore where safety issues can limit access. This can lead to bore abandonment in certain situations.

On top of all this, we have the recent CSIRO study, Potential microbial interactions with cements and steels (March 2024).

It outlines the horrendous unknowns and gaping knowledge gaps when it comes to microbiological activity in the aquifers of Southern Queensland and alludes to the fact that shallow, unconfined aquifers, like the Condamine Alluvium, are at higher risk to Microbial Influenced Corrosion and damage to infrastructure, due to the oxygen and nutrient density (e.g. phosphorous and nitrogen) in these aquifers compared with deeper formations.

As outlined by the CSIRO research team:

“One key concern is that, should corrosion occur, it could impact the integrity of the well, which would potentially damage important groundwater resources on which many communities reply.”

Let’s not forget that the Condamine Alluvium is the most productive alluvium throughout the whole of Queensland, supporting 118,000 hectares of irrigated crops, a billion dollar agricultural industry, as well as a critical water supply to so many regional communities.

With over 3800 water bores in the Alluvium and at a current value of $12,250/ML for permanent allocation water, this is not a trivial concern. The Condamine Alluvium is vital for the ongoing health and economy of this region. The risks to its ongoing integrity must be taken with utmost seriousness, with thorough and appropriate independent risk assessment applied.

Once the egg is scrambled, it cannot be unscrambled.

I recommend you read the entire Potential effects of free gas on bore water supply from CSG development report by KCB, commissioned by the CSG Compliance Unit of the then DNRM.  It’s frank and honest candidness is enlightening, especially when set amongst the more ‘controlled’ reports with their origins linked to gas industry funding which dominate the public domain of today.  It is to be noted that it is thanks to the Basin Sustainability Alliance and the availability of this report on their website, that it is even seeing the light of day, as otherwise it would not be publicly available. 

I look forward to receiving a response to the question raised above and your feedback on the substantial concerns raised as to the future integrity of the Condamine Alluvium and the subsequent longevity of this rich agricultural and closely settled region.

Kind regards

Liza Balmain


The website of CSIRO/GISERA offers access to a number of other reports on the subject, under the umbrella of a project entitled, “Review of cements, steels and microbial activity for Qld CSG wells”.

 


Note also a press release from Saltel Industries in 2019 and an article in Nature which validate their concerns.


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