<div>A prerequisite to understanding the evolution and resource potential of a basin is to establish a reliable stratigraphic framework that enables the correlation of rock units across multiple depocentres. Establishing a stratigraphic model for the Adavale Basin is challenging due to its structurally complexity, lack of well penetration and its lateral changes in facies. Biostratigraphy appears broad-scale, and despite providing chronostratigraphic control for the Lower Devonian Gumbardo Formation when combined with U/Pb zircon geochronology, the rest of the Devonian succession is hampered by a lack of microfossil assemblages and their poor preservation. The aim of this study is to establish an independent chemostratigraphic correlation across the Adavale Basin using whole rock inorganic geochemistry. Within this study, a total of 1489 cuttings samples from 10 study wells were analysed by Inductively Coupled Plasma – Optical Emission Spectrometry and Inductively Coupled Plasma – Mass Spectrometry for whole rock geochemistry, in order to establish an independent chemostratigraphic zonation scheme. Based on key elemental ratios selected to reflect changes in feldspars, clay minerals and provenance, the Devonian-aged stratigraphy is characterised into four chemostratigraphic mega-sequences that encompass the Gumbardo Formation (Mega-sequence 1); the Eastwood Formation, the Log Creek Formation and the Lissoy Sandstone (Mega-sequence 2); the Bury Limestone and the Boree Salt formations (Mega-sequence 3); and the Etonvale and the Buckabie formations (Mega-sequence 4). These mega-sequences have been further subdivided into a series of chemostratigraphic sequences that can be correlated across the study wells, establishing a regional correlation framework.&nbsp;&nbsp;&nbsp;</div> This Paper was submitted/presented to the 2023 Australian Petroleum Production & Exploration Association (APPEA) Conference 15-18 May, (https://www.appea.com.au/appea-event/appea-conference-and-exhibition-2023/). <b>Journal Citation:</b> Riley David, Pearce Tim, Davidson Morven, Sirantoine Eva, Lewis Chris, Wainman Carmine (2023) Application of elemental chemostratigraphy to refine the stratigraphy of the Adavale Basin, Queensland. <i>The APPEA Journal</i><b> 63</b>, 207-219. https://doi.org/10.1071/AJ22108

A large proportion of Australia’s onshore sedimentary basins remain exploration frontiers. Industry interest in these basins has recently increased due to the global and domestic energy demand, and the growth in unconventional hydrocarbon exploration. In 2016 and 2018, Geoscience Australia released an assessment of several central Australian basins that summarised the current status of geoscientific knowledge and petroleum exploration, and the key questions, for each basin. This publication provides a comprehensive assessment of the geology, petroleum systems, exploration status and data coverage for the Adavale Basin.

<div>The Australian Government's Trusted Environmental and Geological Information program is a collaboration between Geoscience Australia and CSIRO. Part of this program includes baseline geological and environmental assessments. </div><div> Hydrogeological information has been collated for the Adavale, Cooper, Galilee and north Bowen basins and overlying basins, including the Eromanga and Lake Eyre basins. This information will provide a regionally-consistent baseline dataset that will be used to develop groundwater conceptualisation models.</div><div> Publicly-available data within these basin regions have been compiled from over 30&nbsp;000 boreholes, 120 stream gauges, and 1100 rainfall stations, resulting in revised hydrostratigraphic frameworks. From the published literature, 14 major hydrostratigraphic units are recognised within the basin regions. For each of these major hydrostratigraphic units, we determined the salinity, Darcian yield, specific yield/storativity, groundwater reserve volume for unallocated groundwater, groundwater levels/hydrological pressure, likelihood of inter-aquifer connectivity, rainfall, connectivity between surface water and groundwater, and water-use volume statistics, where relevant, for each basin, hydrogeological province and aquifer. We then adopted a play-based approach to develop holistic hydrostratigraphic conceptualisations of the basin regions. </div><div> Within the Adavale Basin we have defined a new hydrogeological province including two new aquifers defined as the moderate salinity and moderately overpressured Buckabie-Etonvale Aquifer, and the hypersaline and hyper-overpressured Lissoy-Log Creek-Eastwood Aquifer. Similarities between the upper Buckabie-Etonvale Aquifer of the Adavale Basin and lowermost Joe Joe Group of the Galilee Basin suggests connectivity between the upper Adavale and lower Galilee basins. Hydraulic pressures (up to 1500 m of excess freshwater head) calculated for the Lissoy–Log Creek–Eastwood Aquifer indicate that if the aquifer was to be breached, there is potential localised risk to overlying aquifers and surface environments, including infrastructure.</div><div><br></div><div><strong>Author Biography:</strong></div><div>Dr. Chris Gouramanis is a hydrogeologist working in the Trusted Environmental and Geological Information program, in the Minerals, Energy and Groundwater Division of Geoscience Australia. Chris was awarded his PhD from The Australian National University in 2009 and has held several water and environmental policy positions within the Australian Government. He worked for 10 years as an academic at the Earth Observatory of Singapore and the Geography Department at the National University of Singapore. He is also Australia’s National Focal Point to the Scientific and Technical Review Panel of the Ramsar Convention on Wetlands.</div><div><br></div>This Abstract was submitted/presented to the 2022 Australasian Groundwater Conference 21-23 November (https://agc2022.com.au/)

<div>Two new programs at Geoscience Australia are providing trusted, high-quality science to support decision making and the Australian resources industry. </div><div>&nbsp;</div><div>The Trusted Environmental and Geological Information program will provide baseline pre-competitive data in the Cooper, Adavale, north Bowen and Galilee basin regions. A repository of information is being developed in collaboration with CSIRO, including new geological and environmental assessments, to accelerate development in the sectors of petroleum, mineral, hydrogen and carbon capture and storage, while simultaneously providing opportunities to understand the potential hazards, risk and impacts of these resources being developed.&nbsp;</div><div>&nbsp;</div><div>The Data Driven Discoveries program is combining new and old data to better understand the under-explored Adavale Basin in central-western Queensland. The program will undertake chemical composition analyses to support the correlation of geological layers, collate and reprocess historical seismic data, acquire new seismic reflection data, and undertake stratigraphic research drilling to provide a more detailed understanding of basin architecture and the resource potential of the Adavale Basin. </div><div>&nbsp;</div><div>An overview of the Trusted Environmental and Geological Information and Data Driven Discoveries programs will be provided, including initial results and planned acquisition. This will show how these complementary programs will contribute to streamlined regulation and approval processes, the low emissions agenda, and responsible resource development in key basin regions across Australia.</div> This Abstract was submitted/presented to the 2022 Petroleum Exploration Society of Australia (PESA) QLD Symposium 9 September (https://pesa.com.au/events/pesa-qld-2022-symposium/)

<div>The Adavale Basin is located approximately 850 km west-northwest of Brisbane and southwest of Longreach in south-central Queensland. The basin system covers approximately 100,000 km2 and represents an Early to Late Devonian (Pragian to Famennian) depositional episode, which was terminated in the Famennian by widespread contractional deformation, regional uplift and erosion. </div><div>Burial and thermal history models were constructed for nine wells using existing open file data to assess the lateral variation in maturity and temperature for potential source rocks in the Adavale Basin, and to provide an estimate of the hydrocarbon generation potential in the region.</div>

<div>Geoscience Australia’s Onshore Basin Inventories project delivers a single point of reference and creates a standardised national basin inventory that provides a whole-of-basin catalogue of geology, petroleum systems, exploration status and data coverage of hydrocarbon-prone onshore Australian sedimentary basins. In addition to summarising the current state of knowledge within each basin, the onshore basin inventory reports identify critical science questions and key exploration uncertainties that may help inform future work program planning and decision making for both government and industry. Volume 1 of the inventory covers the McArthur, South Nicholson, Georgina, Wiso, Amadeus, Warburton, Cooper and Galilee basins and Volume 2 expands this list to include the Officer, Perth and onshore Canning basins. Under Geoscience Australia’s Exploring for the Future (EFTF) program, several new onshore basin inventory reports are being delivered. Upcoming releases include the Adavale Basin of southern Queensland, and a compilation report addressing Australia’s poorly understood Mesoproterozoic basins. These are supported by value-add products that address identified data gaps and evolve regional understanding of basin evolution and prospectivity, including petroleum systems modelling, seismic reprocessing and regional geochemical studies. The Onshore Basin Inventories project continues to provide scientific and strategic direction for pre-competitive data acquisition under the EFTF work program, guiding program planning and shaping post-acquisition analysis programs.</div>

<div>As part of the Data Driven Discoveries program, Geoscience Australia and the Geological Survey of Queensland collaborated to re-examine legacy well cuttings for a chemostratigraphic study. The aim was to identify opportunities for resource discovery in the Devonian-aged Adavale Basin in south-central Queensland by conducting a chemostratigraphic study to define regional stratigraphic correlations in a structurally complex basin with limited well penetrations. A total of 1,489 cutting samples were analysed for whole-rock geochemistry, as well as subsets of samples for whole-rock mineralogy and/or carbonate carbon and oxygen isotopes, from a whole-rock sample. The purpose was to establish new chemostratigraphic correlations across the basin independently, using data from 10 wells that sampled the Adavale Basin.</div>

Across Australia, groundwater is a vital resource that supports and strengthens communities, culture, the environment and numerous industries. Movement of groundwater is complicated, taking place horizontally, vertically and across different timescales from weeks to millions of years. It is affected by changes in climate, human use and geological complexities such as the type, geometry and distribution of rocks. Understanding how all these factors interact is known as a groundwater conceptual model and it is an important first step. This groundwater conceptualisation includes the Adavale Basin and the overlying Galilee Basin. Conceptualisation of the Galilee, Eromanga and Lake Eyre basins can be found in Hostetler et al. (2023). In the Adavale Basin this includes 1 aquifer in the Lake Eyre Basin, 5 aquifers in the Eromanga Basin, 3 aquifers in the Galilee Basin and 1 aquifer in the Adavale Basin (Wainman et al., 2023a, b). Confidence for each aquifer was calculated for both salinity and water levels (Gouramanis et al., 2023a, b, c, d). The confidence for each aquifer was added to show the overall confidence for the basin. The level of knowledge across all aquifers are moderate to low. The groundwater conceptualisations summarises the groundwater flow and potential connectivity between aquifers. Figures in this fact sheet show the distribution of the aquifers and aquitards, average salinity, potential aquifer yield and confidence over an area of 50 km along the cross section lines.

Publicly available geological data in the Adavale Basin region are compiled to produce statements of existing knowledge for natural hydrogen, hydrogen storage, coal and mineral occurrences. This data guide also contains an assessment of the potential for carbon dioxide (CO2) geological storage and minerals in the basin region. Geochemical analysis of gas samples from petroleum boreholes in the basin shows various concentrations of natural hydrogen. However, the generation mechanism of the observed natural hydrogen concentration is still unknown. The Adavale Basin also has the potential for underground hydrogen storage in the Boree Salt. Given the depth of the Boree Salt (wells have intersected the salt at depths below 1800 m) and the high fluid pressure gradient in the basin, the construction of underground salt caverns should include consideration of stability and volume shrinkage. Mineral occurrences are all found in the basins overlying the Adavale region. However, they are small (thousands of tonnes range) and not currently of economic interest. The Adavale Basin has potential for base and precious metal deposits due to suitable formation conditions, but the depth of the basin makes exploration and mining difficult and expensive. There are no identified occurrences or resources of coal in the Adavale Basin. Given the depth of the basin, extraction of any identified coal would probably be uneconomic, with the potential exception of coal seam gas extraction. An assessment of CO2 geological storage also shows prospective storage areas in the Eromanga Basin within the Adavale Basin region in the Namur-Murta and Adori-Westbourne play intervals.

Publicly available baseline surface water data are compiled to provide a common information base for resource development and regulatory decisions in the Adavale Basin region. This data guide captures existing knowledge of the catchments and watercourses overlying the Adavale Basin, including streamflow quality and quantity, inundation, and climatological data. The Adavale Basin underlies 3 main surface water catchments that contribute to Cooper Creek, including the Barcoo, Bulloo and Warrego rivers. The Adavale Basin geological boundary also intersects the upper parts of the Paroo River catchment and a small part of the Condamine-Balonne catchment. The data on the catchments overlying the Adavale Basin have been summarised at a point in time to inform decisions on resource development activities. Key data sources are the Water Monitoring Information Portal (Queensland Government), Water Data Online (Bureau of Meteorology), DEA Water Observations (Geoscience Australia) and Terrestrial Ecosystem Research Network.