Evaluating potential coal seam gas impacts to the Condamine Alluvium: an example of successful community involvement

Abstract

The groundwater resources of the Condamine River Alluvial Aquifer (Condamine Alluvium) in Queensland have been developed in the past 60 years for irrigation, stock, domestic and other uses. Extraction of more than 55,000 mL/yr from this aquifer is critical to supporting the local irrigation industry. Existing and proposed coal seam gas development in the Surat Basin extends to underneath the western edge of the CA footprint and involves depressurisation of coals that form up to 10% of the Walloon Coal Measures (WCM) at some depth below the alluvium. Reduced groundwater availability from the already-stressed Condamine Alluvium is thus an oft-quoted concern of landholders when further development of the CSG industry is considered. An extensive study, led by the Queensland Office of Groundwater Impact Assessment (OGIA) and supported by Arrow Energy, was carried out to provide quantitative assessments of vertical hydraulic conductivity between the alluvium, coal measures and intervening formations. This extended abstract focuses on one element of the aforementioned study led by Arrow Energy, specifically, aquifer testing undertaken at two representative sites overlying the Condamine Alluvium. This included drilling and collection of core; geophysical, geomechanical and geochemical testing; test pumping and monitoring; and, modelling. An important element of this project, aside from sharing of data and results—was the involvement of local landholders in development of the investigations, and attendance at field days during drilling and presentation of results. Key findings included estimated ranges of vertical hydraulic conductivity derived from parameter estimation modelling that were lower than previously suggested.