The Geological and Bioregional Assessments (GBA) Program is a series of independent scientific studies undertaken by Geoscience Australia and the CSIRO, supported by the Bureau of Meteorology, and managed by the Department of Agriculture, Water and the Environment. The Program consists of three stages across three regions with potential to deliver gas to the East Coast Gas Market. Stage 1 was a rapid regional prioritisation conducted by Geoscience Australia, to identify those sedimentary basins with the greatest potential to deliver shale and/or tight gas to the East Coast Gas Market within the next five to ten years. This prioritisation process assessed 27 onshore eastern and northern Australian basins with shale and/or tight gas potential. Further screening reduced this to a shortlist of nine basins where exploration was underway. The shortlisted basins were ranked on a number of criteria. The Cooper Basin, the Beetaloo Sub-basin and the Isa Superbasin were selected for more detailed assessment. Stage 2 of the program involved establishing a baseline understanding of the identified regions. Geoscience Australia produced regional geological evaluations and conceptualisations that inform the assessment of shale and/or tight gas prospectivity, ground- and surface-water impacts, and hydraulic fracturing models. Geoscience Australia’s relative prospectivity assessments provide an indication of where viable petroleum plays are most likely to be present. These data indicate areal and stratigraphic constraints that support the program’s further work in Stage 3, on understanding likely development scenarios, impact assessments, and causal pathways. <b>Citation:</b> Hall Lisa S., Orr Meredith L., Lech Megan E., Lewis Steven, Bailey Adam H. E., Owens Ryan, Bradshaw Barry E., Bernardel George (2021) Geological and Bioregional Assessments: assessing the prospectivity for tight, shale and deep-coal resources in the Cooper Basin, Beetaloo Subbasin and Isa Superbasin. <i>The APPEA Journal</i><b> 61</b>, 477-484. https://doi.org/10.1071/AJ20035

An assessment of tight, shale and deep coal gas prospectivity of the Cooper Basin has been undertaken as part of the Australian Government’s Geological and Bioregional Assessment Program. This aims to both encourage exploration and understand the potential impacts of resource development on water and the environment. This appendix presents a review of the regional petroleum prospectivity, its exploration, and the characterisation and analysis of shale, deep coal and tight gas in Carboniferous–Permian Gidgealpa Group of the Cooper Basin. The Cooper Basin is Australia’s premier onshore conventional hydrocarbon-producing province providing domestic gas for the East Coast Gas Market. As of December 2014, the Cooper and Eromanga basins have produced 6.54 Tcf of gas since 1969. The basins contain 256 gas fields as well as 166 oil fields that are currently in production. Gas is predominantly reservoired in the Cooper Basin, whereas the overlying Eromanga Basin hosts mainly oil. Hydrocarbon shows are found in the reservoir units throughout the succession. Recently, exploration targeting a range of unconventional plays has gained momentum. Unconventional play types within the mainly Permian Gidgealpa Group include shale gas associated with the Patchawarra Formation and the Roseneath and Murteree shales, tight and deep coal gas accumulations within the Toolachee, Epsilon and Patchawarra formations and additional tight gas plays in the Daralingie Formation and Tirrawarra Sandstone. To date, at least 80 wells have been drilled to test shale, tight and deep coal gas plays. Given the basin’s existing conventional production, and its processing and pipeline infrastructure, these plays are well placed to be rapidly commercialised, should exploration be successful. A prospectivity confidence mapping workflow was developed to evaluate the regional distribution of key unconventional gas plays within the Gidgealpa Group. For each play type, key physical properties were identified and characterised. The specific physical properties evaluated include formation extents, source rock properties (net thickness, TOC, quality and thermal maturity), reservoir characteristics (porosity, permeability, gas saturation and brittleness), regional stress regime and overpressure. Parameters for mappable physical properties were individually classified to assign prospectivity rankings. Individual properties were then multiplied together produce formation and play-specific prospectivity confidence maps. Non-mappable criteria were not integrated into the prospectivity mapping but were used to better understand the geological characteristics of the formations. Overall, both source and reservoir characteristics were found to be moderately to highly favourable for all play types assessed. Abundant source rocks are present in the Gidgealpa Group across the Cooper Basin. The Toolachee and Patchawarra formations are the richest, thickest and most extensive source rocks, with good to excellent source potential across their entire formation extents. Net shale, coal and sand thicknesses also demonstrate an abundance of potential reservoir units in the Gidgealpa Group across the basin. The predominantly fluvial Toolachee Formation is thickest in the Windorah Trough and Ullenbury Depression. Average effective porosity for assessed tight gas plays ranges from 6.7 % in the fluvio-deltaic to lacustrine Epsilon Formation to 7.8% in the Toolachee Formation. Based on an assessment of the brittleness of the shales and coaly shales, the Patchawarra Formation appears to be most favourable for hydraulic stimulation with an average Brittleness Index of 0.695, indicative of brittle rocks. This compares to the less brittle lacustrine Roseneath and Murteree shales have brittleness indices of 0.343 and 0.374, respectively. As-received total gas content is favourable, with averages ranging from 1.3 scc/g in the Patchawarra Formation to 1.6 scc/g for the Murteree Shale. The regional stress regime has an approximately east-west oriented maximum horizontal stress azimuth, resulting in predominantly strike-slip faulting to reverse faulting, depending on the depth, lithology and proximity of structures, e.g. GMI ridge. Significant overpressure is present at depths greater than 2800 m, especially in the Nappamerri and Patchawarra troughs. Overpressures are generally constrained to the Gidgealpa Group, with the Toolachee Formation being the youngest formation in which significant overpressure has been achieved. Based on a review of the geomechanical properties of the Cooper Basin sedimentary succession, it was found that stress variations within and between lithologies and formations are likely to provide natural barriers to fracture propagation between the gas saturated Permian sediments and the overlying Eromanga Basin. Prospectivity confidence maps were generated for six individual shale and deep coal plays and one combined tight gas play across the Gidgealpa Group. Comparison with key wells targeting shale, tight and deep coal gas plays, indicates that the prospectivity confidence mapping results are largely consistent with exploration activity to-date, with the highest prospectivity confidence for tight, shale and deep coal gas plays mapped in the Nappamerri, Patchawarra, Windorah, Allunga and Wooloo troughs and the southern Ullenbury Depression. Consequently, there is more confidence in the resultant maps in the southern Cooper Basin as more data was available here. Prospectivity confidence maps are relative, therefore a high prospectivity confidence does not equate to 100 % chance of success for a particular formation or play. The outputs of this regional prospectivity assessment identify areas warranting more detailed data collection and exploration and the assessment of potential impacts of resource development on water and the environment. The results also have the potential to encourage further exploration investment in underexplored regions of the Cooper Basin.

High-precision radiometric dating using Chemical Abrasion-Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) has allowed the recalibration of the numerical ages of Permian and Triassic spore-pollen palynozones in Australia. These changes have been significant, with some zonal boundaries in the Permian shifting by as much as six million years, and some in the Triassic by more than twice that. Most of the samples analysed came from eastern Australian coal basins (Sydney, Gunnedah, Bowen, Galilee) where abundant volcanic ash beds occur within the coal-bearing successions. The recalibrations of these widely used palynozones have implications for the dating of geological events outside the basins from where samples were obtained. Our revised dates for the Permian palynozones can now be applied to all Permian basins across Australia, including the Perth, Carnarvon, Canning and Bonaparte basins (along the western and northern continental margins), the Cooper and Galilee basins (in central Australia), and the Bowen, Gunnedah and Sydney basins (in eastern Australia). Revised regional stratigraphic frameworks are presented here for some of these basins. The impact of an improved calibration of biostratigraphic zones to the numerical timescale is broad and far-reaching. For example, the more accurate stratigraphic ages are the more closely burial history modelling will reflect the basin history, thereby providing control on the timing of kerogen maturation, and hydrocarbon expulsion and migration. These improvements can in turn be expected to translate in to improved exploration outcomes. We have initially focused on the Permian and provide preliminary results for the Triassic, but intend to expand recalibrations to include Jurassic, Cretaceous and Paleozoic successions beyond the Permian. Preliminary data indicates that significant changes to these calibrations are also likely.

The Cooper Basin is an upper Carboniferous-Middle Triassic intracratonic basin in northeastern South Australia and southwestern Queensland (Gravestock et al., 1998; Draper, 2002; McKellar, 2013; Carr et al., 2016; Hall et al., 2015a). The basin is Australia's premier onshore hydrocarbon producing province and is nationally significant in providing gas to the eastern Australian gas market. The basin also hosts a range of unconventional gas play types within the Permian Gidgealpa Group, including basin-centred gas and tight gas accumulations, deep dry coal gas associated with the Patchawarra and Toolachee formations, the Murteree and Roseneath shale gas plays and deep coal seam gas in the Weena Trough (e.g. Goldstein et al., 2012; Menpes et al., 2013; Greenstreet, 2015). The principal source rocks for these plays are the Permian coals and coaly shales of the Gidgealpa Group (Boreham & Hill, 1998; Deighton et al., 2003; Hall et al., 2016a). Mapping the petroleum generation potential of these source rocks is critical for understanding the hydrocarbon prospectivity of the basin. Geoscience Australia, in conjunction with the Department of State Development, South Australia and the Geological Survey of Queensland, have recently released a series of studies reviewing the distribution, type, quality, maturity and generation potential of the Cooper Basin source rocks (Hall et al., 2015a; 2016a; 2016b, 2016c; 2016d). Petroleum systems models, incorporating new Cooper Basin kinetics (Mahlstedt et al., 2015), highlight the variability in burial, thermal and hydrocarbon generation histories for each source rock across the basin (Hall et al., 2016a). A Geoscience Australia record 'Cooper Basin Petroleum Systems Analysis: Regional Hydrocarbon Prospectivity of the Cooper Basin, Part 3' providing full documentation of the model input data, workflow and results is currently in press. This work provides important insights into the hydrocarbon prospectivity of the basin (Hall et al., 2015b; Kuske et al., 2015). This product contains the working Cooper Basin Trinity-Genesis-KinEx petroleum systems model used to generate the results presented in these studies. This includes maps describing thickness, TOC and original HI for the following Permian source intervals: Toolachee Fm coals and coaly shales Daralingie Fm coals and coaly shales Roseneath Shale Epsilon Fm coals and coaly shales Murteree Shale Patchawarra Fm coals and coaly shales This model is designed for use as a regional scale hydrocarbon prospectivity screening tool. Model resolution is not high enough for this product to be used for sub-basin to prospect scale analysis, without further modification. However, the model provides a regional framework, into which more detailed prospect scale data may be embedded. The systematic workflow applied demonstrates the importance of integrated geochemical and petroleum systems modelling studies as a predictive tool for understanding the petroleum resource potential of Australia's sedimentary basins.

Publicly available data was compiled to provide a common information base for resource development, and environmental and regulatory decisions in the Cooper Basin. This web service summarises the geological storage of carbon dioxide prospectivity of the Cooper Basin.

Publicly available data was compiled to provide a common information base for resource development, and environmental and regulatory decisions in the Cooper Basin. This web service summarises the geological storage of carbon dioxide prospectivity of the Cooper Basin.

Publicly available geological data in the Cooper Basin region are compiled to produce statements of existing knowledge for natural hydrogen, hydrogen storage, coal and mineral occurrences. This web service summarises mineral potential in the Cooper Basin region.

Publicly available geology data are compiled to provide a common information base for resource development and regulatory decisions in the Cooper Basin region. This data guide gives examples of how the compiled data can be used. It supports a data package that presents core photographs, existing knowledge of the stratigraphy, and structural elements for the Cooper Basin and the overlying Simpson, Eromanga and Lake Eyre basins. Stratigraphic frameworks capture the geological groups and formations that make up the sedimentary sequence in the Cooper Basin region. The Cooper Basin includes 2 stratigraphic groups. From deepest to shallowest, these are the Gidgealpa Group and the Nappamerri Group. The overlying Cuddapan Formation is considered part of the Simpson Basin instead of the Cooper Basin. Overlying the Cooper Basin are the geological formations of the Eromanga and Lake Eyre basins. The frameworks include the stratigraphic intervals used by the Trusted Environmental and Geological Information (TEGI) Program. From the base of the Cooper Basin to the top of the Lake Eyre Basin, the sedimentary sequence is categorised into 16 play intervals for resource assessment mapping and 9 hydrostratigraphic intervals for characterising groundwater systems (Wainman et al., 2023). Structural elements maps summarise where the sedimentary sequence has been deposited and later deformed by crustal movements. Structure information is used in assessing the geological potential for resources and interpreting groundwater flow and connectivity at the basin scale. The stratigraphic frameworks and structural elements provide the basic geological context for the Cooper Basin region geological, resource and environmental assessments.

The potential for hydrogen production in the Cooper Basin region is assessed to provide a joint information base for hydrogen generation potential from renewable energy, groundwater, and natural gas coupled with carbon capture and storage (CCS). Hydrogen generation requires water, whether using electrolysis with renewable energy or steam methane reforming (SMR) of gas with CCS. The data package includes the regional renewable energy capacity factor, aquifers and their properties (potential yield, salinity, and reserves or storativity), and geological storage potential of carbon dioxide (CO2). This data guide gives examples of how the compiled data can be used. The renewable hydrogen potential is assessed based on renewable energy capacity factor and groundwater information (potential yield, salinity, and reserves or storativity). Three aquifers from overlying basins (Eromanga and Lake Eyre basins) are included in the assessment. The Cooper Basin region has high renewable hydrogen potential. The presence of good aquifer throughout the basin combined with high renewable energy capacity factor resulted in significant areas with high hydrogen potential. The Cooper Basin has significant hydrocarbon resources, primarily for gas (Geoscience Australia, 2022). Although most known hydrocarbon resources have depleted since production began in the 1960s (Smith et al., 2015), a large amount of gas remains, including conventional gas (1,058 PJ reserves and 1,598 PJ resources) and unconventional basin-centred gas (2,265 PJ resources). An assessment in the overlying Eromanga Basin suggests that most areas over the Cooper Basin are prospective for potential CO2 geological storage (Bradshaw et al., 2023). Further work on identifying detailed gas potential is needed to assess hydrogen generation potential from SMR coupled with CCS.

Publicly available baseline ecology data are compiled to provide a common information base for environmental, resource development and regulatory decisions in the Cooper Basin region. This data guide captures existing knowledge of the ecosystems and environmental assets overlying the Cooper Basin. The land overlying the Cooper Basin is dominated by the Channel Country, Simpson Strzelecki Dunefields and Mulga Lands Interim Biogeographic Regionalisation for Australia (IBRA) bioregions with small areas of Mitchell Grass Downs and Stony Plains bioregions. The data on the ecosystems and environmental assets overlying the Cooper Basin have been summarised in July 2021 to inform decisions on resource development activities. Key data sources are broad vegetation groups - pre-clearing and 2019 remnant - Queensland series (Queensland Government), Field Environmental Data, Australian Wetlands Database and Heritage places and lists (Department of Climate Change, Energy, the Environment and Water), and the Atlas of Living Australia.