Roadshow 2.4 Assessing potential impacts on water and the environment from shale and tight gas development in the Beetaloo GBA region

Assessing potential impacts on water and the environment from shale and tight gas development in the Beetaloo GBA region

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Hi, I'm Cameron Huddlestone-Holmes and I led the Beetaloo region component of the Geological and Bioregional Assessment, or GBA program. I'm going to give you an overview of the program's work in the Beetaloo GBA region.

The aim of the GBA program was to assess the potential impacts of unconventional gas development on water and the environment, providing information to help decision makers from government and the industry to better understand where to look more closely, where risks of wide concern when they're assessing development proposals in the future.

GBA assessments also provide information to other stakeholders, including the broader community about potential impacts of future resource development. The program ran for four years and involved around 100 scientists from CSIRO and Geoscience Australia. We have also collaborated with experts from our technical peer review group and the state, territory, and Commonwealth governments and engaged with regional communities and stakeholders.

GBA program started in 2017 and comprised of three stages. The first stage evaluated the potential of onshore basins delivering gas to the east coast gas market. The Beetaloo Sub-basin was one of three regions selected for further assessment by the program.

In stage two, we compiled existing information in a geological and environmental baseline assessment for the region, providing the basis for the stage three assessments and associated studies.

Stage three of the GBA program was an assessment of potential impacts from unconventional gas resource development. The assessment was conducted using a new method developed for this project that uses a spatial causal network to look at the links between development activities and the environmental matters we want to protect. The complete assessment is available through an innovative and interactive web-based tool, the GBA Explorer.

The Beetaloo Sub-basin, shown on this map by the green outline, lies within the McArthur Basin. In stage one, this basin was ranked high for prospectivity and medium for confidence, reflecting the level of exploration undertaken in the basin and exploration successes to date. There's no existing conventional oil/gas production in this basin and an interesting feature of it is the age of the rocks, which is significantly older than most other resources on a global scale.

Further assessment of geology and prospectivity in stage two looked at several unconventional gas play types, including shale and tight gas, all with a liquids component. The whole basin is prospective and it's not really possible to rule out any areas for future development.

As part of the stage two geological and environmental baseline assessment, looked at the water resources within the Beetaloo GBA region. The Cambrian Limestone Aquifer, shown here in this 3D representation of the region in blue, is the main water resource. It is primarily used for stock watering and is shallow compared to the gas resources of the Kyalla and Velkerri formations, shown here in green and orange. There is limited surface water within the region due to the low rainfall, the fact that it's a tableland and the fact that the groundwater table is quite deep.

The use of surface water for unconventional gas resource operations is prohibited in the Northern Territory and so, groundwater will be the main source of water for our future industry. There is limited evidence of connectivity between the deeper groundwater systems and the Cambrian Limestone Aquifer. These connections were investigated further in stage three.

As part of our ecological studies in the stage two assessment, we looked at the landscape classes for the Beetaloo GBA region. The region is quite uniform and is predominantly loamy and sandy plains and clay pans. Further work is being done looking at the landscape classes as part of the ecological baseline surveys conducted in conjunction with GBA and will likely be further refined as part of the strategic regional and environmental baseline assessments that the Northern Territory is conducting.

In stage two, we looked at the protective matters within the region. This included 45 species and nine areas protected under either the EPBC Act or NT legislation. We prioritised six protected species and two areas for further study as part of stage three.

Here are the six protected matters that we identified for further study as part of stage three. I should note that the Gulf snapping turtle was added after stage two, as it was identified within the region as part of the ecological baseline surveys.

We conducted a hazard identification exercise as part of stage two, where we systematically identified the ways in which unconventional gas resource development may impact ecological, economic and social values. This hazard identification formed a starting point for the assessment in stage three and also helped to identify any knowledge gaps that would require further investigation.

We also conducted a chemical screening, which was a tier one qualitative environmental risk assessment that looked at 116 chemicals associated with drilling and hydraulic fracturing in unconventional gas resource operations. This screening found 42 chemicals were of low concern and posed minimal risk to aquatic ecosystems. A further 33 chemicals were of potential high concern and 41 were of potential concern.

Further assessment, including sampling, was conducted in stage three within the Beetaloo GBA region. We also reviewed nine domestic and international inquiries into unconventional gas industry operations and also looked at historical data. This review found that the likelihood of hydraulic fracture growth into an aquifer or a well or a fault is low. The review also found that well integrity is closely regulated and is of low concern.

In stage three of the GBA program, we conducted an assessment of the potential impacts of unconventional gas resource development on water and the environment. We did this using the spatial causal network method developed as part of the program. You can see here the causal network that we developed for the Beetaloo GBA region. This network consists of 62 nodes and 197 links that make up 2,078 pathways, linking the driver through activities, stressors, processes, to the endpoints which are the matters that we care about. Each link is evaluated using a 500 metre by 500 metre grid that covers the entire 80,500 square kilometres of the Beetaloo GBA extended region. This region matches the extents of the strategic, regional and environmental baseline assessment area as it stood prior to amendments in late 2020.

There are hundreds of maps showing where impacts could occur, as well as link evaluation and contextual maps used to build the causal network. The causal network identifies potential impact pathways and mitigation options along each of those pathways. The causal network and the information contained within it provides a comprehensive baseline for decision makers. You can go and explore the GBA Explorer and you can find it just simply by searching for GBA Explorer in your search engine of choice.

For our assessment, we used a resource development scenario that is similar to the one used by the Pepper Inquiry, that considers around about 365 petajoules of gas production per year from the Beetaloo region. Based on this scenario, we worked out how many wells, well pads, access tracks would be required and how much water is needed for the development. Access tracks and well pads could disturb up to 32 square kilometres under this scenario.

Impacts could occur where development occurs or in adjacent areas. We found that all potential impact pathways have mitigation options for existing regulatory controls and industry practice. This finding does emphasise the importance of compliance with regulatory controls and their enforcement, along with continued monitoring of their effectiveness.

Stage three also included a number of investigations to support the overall assessment. Each investigation is summarised in a two page fact sheet that gives a high level overview and links to the data sets, journal papers and reports for each of those investigations. In the Beetaloo region, these investigations included a hydraulic fracturing chemical assessment, which involved detailed sampling of flowback water, sampling of monitoring and landholder bores and monitoring of the impacts of spills. We also developed environmental accounts as a way of monitoring ecosystem health. We conducted additional studies on regional aquifers, including the sources of water at the Mataranka springs, the recharge processes for the Cambrian Limestone Aquifer, modelling of groundwater extraction for resource development, as well as connectivity to deep and shallow aquifers.

The GBA program was extended with funding for five additional activities in the Beetaloo GBA region. These were a baseline ecological survey, water characterization and discharge studies from the Cambrian Limestone Aquifer, testing new remote sensing methods for monitoring habitat, seismic monitoring and development of a data management platform for the NT. We can see some of the data collected by the seismic network and that's part of the remote sensing study here.

In conclusion, environmental impact assessments are complex. Through this program, we have developed a method that allows us to unravel that complexity and look at the pathways by which development activities may have an impact on the environment matters that we care about. We are able to see the pathways which need the most attention and those which we need to worry less about. We can also see where management is critical and ongoing monitoring will be required.

Our assessment shows that while impacts can occur, they can be mitigated by existing controls. This reinforces the need for those existing controls to be in place and for ongoing monitoring of their effectiveness. Our assessment provides a comprehensive baseline for decision makers as they look at future developments in the Beetaloo GBA region. Our assessment was supported by a number of investigations to address knowledge gaps, which involved the input of many individuals, including local community, stakeholders and experts.

I'd also like to acknowledge the contributions from our stakeholders within the region, including traditional owners, members of the regional community, as well as government, industry, representatives of other land users, and our technical peer review group. Thank you.

Additional information

About the presenter 

Dr Cameron Huddlestone-Holmes 


Cameron is a Senior Research Scientist in CSIRO who works on environmental, geological and geotechnical problems in the earth resources industry, primarily in the unconventional gas, coal and geothermal sectors. His specialty is in integrating multi-disciplinary capabilities in geoscience and resource engineering and applying them to solving problems in industry. 

Last updated:
15 November 2021