Cooper Basin
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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.
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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.
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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.
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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). This web service summarises hydrogen potential in the Cooper Basin region.
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The Cooper Basin is a Pennsylvanian to Middle Triassic intracratonic basin in northeastern South Australia and southwestern Queensland (Gravestock et al., 1998; Draper, 2002). Exploration activity in the region has recently expanded with explorers pursuing a range of newly-identified unconventional hydrocarbon plays (Goldstein et al., 2012; Menpes et al., 2013; Greenstreet, 2015; Carr et al., 2016). In support of this on-going exploration activity, Hall et al. (2015a) presented a regional overview of the architecture, tectonic evolution and lithostratigraphy of the Cooper Basin. This data pack contains the supplementary material accompanying this report. Structural architecture, extent and thickness of key stratigraphic units were characterised through construction of a regional 3D geological model, designed to capture the groups and formations associated with the major play types in the basin (Hall et al., 2015a). Existing published Cooper Basin horizons (DMITRE, 2001, 2009; NGMA, 2001) were integrated with stratigraphic tops (DNRM, 2015; DSD, 2015) and new seismic data interpretations, ensuring seamless integration of datasets across the state border. Isopachs extracted from the 3D model were used to review the extent and true vertical thickness of each stratigraphic unit. The Permian Toolachee and Patchawarra formations in Queensland are shown to have a wider extent compared with previous studies. The boundaries of the Roseneath and Murteree shales were revised, although their distribution still remains uncertain in areas such as the Arrabury Depression. Lithofacies analysis published for South Australia (Sun & Camac, 2004) were integrated with new stratigraphic analysis in the Weena Trough (Morton, 2016) and new electrofacies mapping in Queensland to produce the first basin wide set of lithofacies maps for the Toolachee, Daralingie, Epsilon and Patchawarra formations (Hall et al., 2015a). The resulting net sandstone, siltstone, shale and coal thickness maps characterise the regional distribution of key source, reservoir and seal units across the basin. Maps of net coal and shale thickness demonstrate an abundance of potential source rock facies in the Toolachee and Patchawarra formations in all regions. Additional potential source rock facies can be found in the Roseneath and Murteree shales, as well as in coals and shales of the Daralingie and Epsilon formations. Net sandstone thickness maps highlight possible regional reservoir facies distribution. The model is designed to characterise the formations associated with the basin's key petroleum systems elements, providing a framework for regional scale petroleum systems analysis and resource assessment studies (Hall et al., 2015b; Kuske et al., 2015). While this work provides important insights into both the conventional and unconventional hydrocarbon prospectivity of the basin, it also has application for the assessment of other resources such as groundwater (e.g. Smith et al., 2015a, b, c).
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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.
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Publicly available geology data are compiled to provide a common information base for resource development, environmental and regulatory decisions in the Cooper Basin region. This data guide gives examples of how these data can be used and supports the data package that provides the existing knowledge of the key geological intervals of the Cooper Basin and the overlying Eromanga and Lake Eyre basins. The key geological intervals identified by the Trusted Environmental and Geological Information (TEGI) Program for resource assessment and groundwater system characterisation are termed play intervals and hydrostratigraphic intervals respectively. The Cooper Basin includes 7 plays, which are consolidated into 1 hydrostratigraphic interval. Overlying the Cooper Basin are 9 play intervals of the Eromanga Basin, which are consolidated into 7 hydrostratigraphic intervals and 1 Cenozoic play interval and 1 hydrostratigraphic interval for the Lake Eyre Basin. The geological groups and formations included in the play and hydrostratigraphic intervals are summarised in the stratigraphic charts of Wainman et al. (2023). Gross depositional, depth structure and thickness maps are provided with 3D model and cross-sections summarising the geology of the Cooper Basin and the overlying basins. The mapped depths and thicknesses of the key intervals are used to inform resource assessments and provide the framework for assigning groundwater data to hydrostratigraphic intervals.
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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.
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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.
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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 web service summarises existing knowledge of the ecosystems and environmental assets in the Cooper Basin region.