By analysing groundwater hydrochemical data, methane and environmental tracers, we provide scientific evidence about the significance of aquifer connectivity, or lack thereof, to strengthen decision making around natural gas investments.

The challenge

Investments in natural gas projects are halted by lack of understanding of potential impacts on groundwater resources

Hydrocarbon resource developments in Australia worth trillions of dollars are currently being proven. Many of these can only proceed if it can be demonstrated that impacts on groundwater and other water resources and dependent ecosystems are negligible.

The key to unlocking future investment and economic growth rests on industry's capacity to retain a 'social licence to operate' across the full life cycle of exploration, operation and closure.

Communities are concerned that drilling and rock fracturing will result in contamination of relatively uncontaminated aquifers and that contaminated fluids may reach adjacent aquifers supplying agriculture and towns.

Groundwater hydrochemistry combined with environmental tracers and methane data are a key tool for studying the connectivity, or lack thereof, of gas reservoirs with adjacent aquifers.

Our response

Baseline hydrochemistry builds confidence around inter-aquifer connectivity

 ©Mat Gilfedder

One of the major concerns in areas of coal seam gas development is around methane in water bores. Methane in water bores can come from natural (shallow and deep) and human‑made sources. In some cases, it has formed over millions of years from decomposing organic matter held under high temperatures and pressures (thermogenic methane).

To understand whether methane in water bores is a concern already or whether it is getting worse requires understanding of sources of methane gas in the subsurface and use of state-of-the-art methods for measuring gas in water bores. To distinguish whether any increases are due to CSG or any other processes, methane identification methods are needed to separate the impacts of CSG developments from other processes such as existing water extraction. This will help distinguish where methane is coming from and whether it is being mixed, diluted or transformed along the way.

Our analysis of groundwater hydrochemistry, environmental tracers and methane gas have provided pivotal information to decide about the sources of methane and if the sealing capacity of aquitards separating the target gas formations from groundwater aquifers is adequate for groundwater protection.

Based on analysis of baseline information, an appropriate monitoring, management and response strategy can be developed, commensurate with the risks.

The results

Management decisions underpinned by robust scientific evidence

The engagement

CSIRO engaged closely with Federal and State Governments and industry to deliver robust scientific evidence providing greater confidence about the impacts of resource developments.

Working with the Queensland Department of Natural Resources and Mines has resulted in the development of a decision support system on which to base the determination of coal seam gas operations as a likely cause of increased gas in water bores.

Working with the Commonwealth Department of Environment and Energy on regional-scale impacts of faults and aquitards in the context of coal seam gas extraction has culminated in new knowledge generation in hydrogeology, groundwater management and sustainable resource extraction, and thereby assist better decision-making, regulation, natural resource management and industry practice.

The impact

Our integrated analysis of groundwater hydrochemistry, tracers and methane gas will strengthen:

  • regulator advice on project proposals with regard to the adequacy of methods of assessment and representation of groundwater flow across low permeability formations (aquitards)
  • regulator and industry understanding of coal reservoir behaviour as it relates to depressurisation and water production, and how perturbations within the reservoir are propagated across aquitards into overlying and underlying water resources.

The insights gained through this work will lead to greater community confidence in and understanding of the science underpinning controversial industrial processes such as CSG and shale gas and their impact on groundwater systems.

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