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.

This appendix provides a regional geological analysis and conceptualisation of the Cooper GBA region. It delivers information critical for the shale, tight and deep coal gas prospectivity assessment outlined in the petroleum prospectivity technical appendix (Lech et al., 2019), and for input into assessing the potential impacts on groundwater and surface water assets detailed in the hydrogeology (Evans et al., 2019) and hydraulic fracturing (Kear et al., 2019) technical appendices. The Cooper Basin is a Carboniferous to Triassic intracratonic basin in north-eastern South Australia and south-western Queensland. It has a total area of approximately 127,000 km2, of which about three quarters lies within Queensland and the remainder lies within South Australia. Section 2 provides a comprehensive inventory and review of existing open data and information for the Cooper GBA region relevant for the prospectivity assessment (see the petroleum prospectivity technical appendix (Lech et al., 2019)) and hydrogeological characterisation (see the hydrogeology technical appendix (Evans et al., 2019)). It includes discussion of the datasets incorporated in the data inventory. A broad range of datasets were utilised to develop a three-dimensional conceptualisation of the geological basin. These include: geographic and cultural datasets which details the location and nature of administrative boundaries, infrastructure and topography; and geological datasets such as surface geology and geological provinces, well and seismic data and geophysical data. A range of public domain publications, reports and data packages for the Cooper Basin are also utilised to characterise the basin architecture and evolution. Section 3 reviews the Cooper Basin’s geological setting and the GBA region’s basin evolution from pre-Permian basement to creation of the Cooper, Eromanga and Lake Eyre basins. Section 4 reviews the main structural elements of the Cooper Basin and how these relate to the basin’s stratigraphy and evolution. The base of the Cooper Basin succession sits at depths of up to 4500 m, and reaches thicknesses in excess of 2400 m. The Cooper Basin is divided into north-eastern and south-western areas, which show different structural and sedimentary histories, and are separated by a series of north-west–south-east trending ridges. In the south-west the Cooper Basin unconformably overlies lower Paleozoic sediments of the Warburton Basin, and includes three major troughs (Patchawarra, Nappamerri and Tenappera troughs) separated by ridges (the Gidgealpa–Merrimelia–Innamincka and Murteree ridges). The depocentres include a thick succession of Permian to Triassic sediments (the Gidgealpa and Nappamerri groups) deposited in fluvio-glacial to fluvio-lacustrine and deltaic environments. The north-eastern Cooper Basin overlies Devonian sediments associated with the Adavale Basin. Here the Permian succession is thinner than in the south-west, and the major depocentres, including the Windorah Trough and Ullenbury Depression, are generally less well defined. The Cooper Basin is entirely and disconformably overlain by the Jurassic–Cretaceous Eromanga Basin. In the Cooper GBA region the Eromanga Basin includes two major depocentres, the Central Eromanga Depocentre and the Poolowanna Trough, and exceeds thicknesses of 2500 m. Deposition within the Eromanga Basin was relatively continuous and widespread and was controlled by subsidence rates and plate tectonic events along the eastern margins of the Australian Plate. The Eromanga Basin is comprised of a succession of terrestrial and marine origin. It includes a basal succession of terrestrial sedimentary rocks, followed by a middle marine succession, then finally an upper terrestrial succession. The Lake Eyre Basin is a Cenozoic sedimentary succession overlying the Eromanga Basin, covering parts of northern and eastern South Australia, south-eastern Northern Territory, western Queensland and north-western New South Wales. The Lake Eyre Basin is subdivided into sub-basins, with the northern part of the Callabonna Sub-basin overlying the Cooper Basin. Here the basin is up to 300 m thick and contains sediments deposited from the Paleocene through to the Quaternary. Deposition within the Lake Eyre Basin is recognised to have occurred in three phases, punctuated by periods of tectonic activity and deep weathering. This technical appendix provides the conceptual framework to better understand the potential connectivity between the Cooper Basin and overlying aquifers of the Great Artesian Basin and to help understand potential impacts of shale, tight and deep coal gas development on water and water-dependent assets.

Geoscience Australia recently commenced work on a multi-year study of Australian petroleum source rocks to improve our understanding of the petroleum resource potential of Australia's sedimentary basins. The Permian source rocks of the Cooper Basin are the first to be characterised for this project. Quantifying the spatial distribution and petroleum generation potential of these source rocks is critical for understanding both the conventional and unconventional hydrocarbon prospectivity of the basin. 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., 2015; 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 contains reviews the distribution, type, quality, maturity and generation potential of the Cooper Basin source rocks. 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. - A 3D basin model, characterising regional basin architecture, was constructed through the integration of existing horizons with formation tops and seismic interpretations (Hall et al., 2015a; Hall et al., 2016d). - Source rock distribution, amount and quality were reviewed through the analysis of log data and source rock geochemical data (including data acquired from new sampling), characterising source rocks across the whole basin (Hall et al., 2016a; Hall et al., 2016e). - 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., 2016b in prep; Hall et al., 2016f). This GIS contains all data associated with the above reports and accompanying data packages, providing important insights into the hydrocarbon prospectivity of the basin (Hall et al., 2015b; Kuske et al., 2015). The broad extent of the Cooper Basin's Permian source kitchen and its large total generation potential, highlights the basin's significance as a world class hydrocarbon province. The systematic workflow applied here 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.

The Cooper Basin is an upper Carboniferous to Middle Triassic intracratonic basin in northeastern South Australia and southwestern Queensland (Gravestock et al., 1998; Draper, 2002; Carr et al., 2016). 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 & Hill, 1998; Deighton et al., 2003). Hall et al. (2016a) reviews the maturity and generation potential of the Cooper Basin source rocks and is the third part of a series of reports reviewing various aspects of the hydrocarbon prospectivity of the Cooper Basin (see also Hall et al., 2015a; Hall et al., 2016a). This data pack contains the supplementary material accompanying this report. Over ninety 1D thermal and burial history models were integrated with the 3D basin model and source rock property characteristics to create a regional multi-1D petroleum systems model for the basin. The burial and thermal history of the model was calibrated using present day corrected temperatures and maturity indicators (Ro, Tmax). In addition lithologies for key wells were calibrated using velocity, density and thermal conductivity data. Thermal boundary conditions were modelled as transient heat-flow from base lithosphere. Crustal thickness and radiogenic heat production properties were used from published studies (e.g. Beardsmore, 2004; Meixner et al., 2012; Hall et al. 2015a). The 1D models are integrated with a 3D regional basin model (Hall et al., 2015a) to create a multi-1D petroleum systems model of the Cooper Basin. Parameters for source rock distribution, amount and quality were added from analysis of log data and source rock geochemical data (Hall et al., 2016a) and new Cooper Basin kinetics (Mahlstedt et al., 2015). This data pack includes the following grids for each source rock: temperature (°C), maturity (%Ro), transformation ratio (%), total hydrocarbon generation (mmboe/km2), oil expelled (mmbbl/km2), gas expelled (mmboe/km2; bcf/km2), oil retained (mmbbl/km2) and gas retailed (mmboe/km2; bcf/km2). The results quantify both the maturity and total maximum hydrocarbon yield of each source rock, providing important insights into the hydrocarbon prospectivity of the basin (Hall et al., 2015b; Kuske et al., 2015).

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 groundwater data have been compiled to provide a common information base to inform environmental, resource development and regulatory decisions in the Cooper Basin region. This web service summarises salinity and water levels for the Cooper Basin located within the Cooper Basin region.

Publicly available groundwater data have been compiled to provide a common information base to inform environmental, resource development and regulatory decisions in the Cooper Basin region. This web service summarises salinity, water levels, resource size, potential aquifer yield and surface water–groundwater interactions for the Eromanga Basin located within 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 web service summarises the geology of the Cooper Basin.

Publicly available geology data are compiled to provide a common information base for resource development and regulatory decisions in the Cooper Basin region. This web service summarises the geology of the Cooper Basin.