Pedirka Basin
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<div>This document provides metadata for the gross depositional environment (GDE) interpretations that have been generated in support of the energy resource assessments under the Australia’s Future Energy Resources (AFER) project. </div><div>The AFER projects is part of Geoscience Australia’s Exploring for the Future (EFTF) Program—an eight year, $225 million Australian Government funded geoscience data and precompetitive information acquisition program to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This will help support a strong economy, resilient society and sustainable environment for the benefit of all Australians. The EFTF program is supporting Australia’s transition to a low emissions economy, industry and agriculture sectors, as well as economic opportunities and social benefits for Australia’s regional and remote communities. Further details are available at http://www.ga.gov.au/eftf. </div><div>The GDE data sets provide high level classifications of interpreted environments where sediments were deposited within each defined play interval in the Pedirka, Simpson and Western Eromanga basins. Twelve gross depositional environments have been interpreted and mapped in the study (Table 1). A total of 14 play intervals have been defined for the Pedirka, Simpson and Western Eromanga basins by Bradshaw et al. (2022, in press), which represent the main chronostratigraphic units separated by unconformities or flooding surfaces generated during major tectonic or global sea level events (Figure 1). These play intervals define regionally significant reservoirs for hydrocarbon accumulations or CO2 geological storage intervals, and often also include an associated intraformational or regional seal. </div><div>GDE interpretations are a key data set for play-based resources assessments in helping to constrain reservoir presence. The GDE maps also provide zero edges showing the interpreted maximum extent of each play interval, which is essential information for play-based resource assessments, and for constructing accurate depth and thickness grids. </div><div>GDE interpretations for the AFER Project are based on integrated interpretations of well log and seismic data, together with any supporting palynological data. Some play intervals also have surface exposures within the study area which can provide additional published paleo-environmental data. The Pedirka, Simpson and Western Eromanga basins are underexplored and contain a relatively sparse interpreted data set of 42 wells and 233 seismic lines (Figure 2). Well and outcrop data provide the primary controls on paleo-environment interpretations, while seismic interpretations constrain the interpreted zero edges for each play interval. The sparse nature of seismic and well data in the study area means there is some uncertainty in the extents of the mapped GDE’s. </div><div>The data package includes the following datasets: </div><div>Play interval tops for each of the 42 wells interpreted – provided as an ‘xlsx’ file. </div><div>A point file (AFER_Wells_GDE) capturing the GDE interpretation for each of the 14 play intervals in each of the 42 wells – provided as both a shapefile and within the AFER_GDE_Maps geodatabase. </div><div>Gross depositional environment maps for each of the 14 play intervals (note that separate GDE maps have been generated for the Namur Sandstone and Murta Formation within the Namur-Murta play interval, and for the Adori Sandstone and Westbourne Formation within the Adori-Westbourne play interval) – provided as both shapefiles and within the AFER_GDE_Maps geodatabase. </div><div> </div><div>These GDE data sets are being used to support the AFER Project’s play-based energy resource assessments in the Western Eromanga, Pedirka and Simpson basins. </div><div><br></div>
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<div>Identifying potential basin areas for future Geological Storage of CO2 (GSC) exploration is essential to support Australia’s transition to a net zero emissions energy future. Geoscience Australia’s AFER Project has completed a play-based assessment of the GSC potential in the Pedirka and western Eromanga basins using regionally extensive aquifers containing saline to slightly brackish formation waters. There are currently no significant anthropogenic CO2 sources or associated storage projects in the assessment area. Understanding the area’s GSC potential does, however, assist in providing options for addressing CCS requirements in the central Australian region, including any future opportunities to remove anthropogenic CO2 using Direct Air Capture and Storage technologies. </div><div><br></div><div>The AFER Project’s assessments are underpinned by new geological insights into the basins and a supporting upscaled 3D geological model. A play-based common risk segment mapping approach has been applied to five potential storage (play) intervals to delineate basin areas with relatively high prospectivity based on four geological risk elements: injectivity, storage effectiveness, containment, and structural complexity. Results from this qualitative component of the assessment highlights a potentially prospective area for future GSC exploration extending across the Northern Territory, South Australia and Queensland. The most prospective interval on a geological probability of success basis is the Namur-Murta play interval. </div><div><br></div><div>Results from the qualitative GSC assessment have been used as a screening tool to delineate areas for quantitative modelling of the range of Estimated Ultimate Storage (EUS) volumes using deterministic and probabilistic methodologies. EUS volumes have been estimated in two model areas representing geological end members in storage interval heterogeneity and potentially prospective areas outside of the extents of current national parks. The EUS potential is high (10’s of gigatonnes) in the two model areas using both deterministic and probabilistic workflows, as expected for a regional assessment using very large pore volumes. Applying a geological probability of success based on injectivity and structural and stratigraphic containment reduces the volumes in the two model areas to a risked best estimate EUS of 13 Gt in the eastern area and a risked best estimate EUS of 2 Gt in the western area. Results from the quantitative assessment suggest that both model areas can support multiple industrial-scale CCS projects injecting 50 Mt CO2 over a 20-year period. However, heterogeneous reservoirs that extend over the eastern assessment area are likely to have greater storage efficiencies and an associated smaller project footprint of 29 km2 using three CO2 injection wells. Relatively homogenous reservoirs elsewhere in the assessment area have lower storage efficiencies due to a lack of intraformational seals within the Algebuckina Sandstone and have an associated larger project area of 49 km2 using three CO2 injection wells. Pressure management requirements are likely to be minimal in both model areas due to the thick and open nature of reservoirs. However, water production rates of up to 16,500 m3/day may be required where local lateral barriers to pressure dissipation occur. </div><div><br></div><div>Results from the AFER Project's GSC assessment demonstrate the value of applying a play-based exploration workflow for a regional-scale energy resource assessment. Estimating the geological probability of success to the presence and repeatability of four mappable risk elements associated with GSC resources allows both relative prospectivity maps and risked EUS volumes to be generated. Prospectivity maps and EUS volumes can in turn be readily updated as new geological data are collected to infill data and knowledge gaps. Geoscience Australia is building a national inventory of GSC resources using this play-based exploration approach, with qualitative assessments now completed under the EFTF and TEGI programs in seven basin areas from central and eastern Australia. </div><div><br></div>
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<div>As part of the Exploring For The Future (EFTF) program, the Australia’s Future Energy Resources (AFER) project has investigated the potential of energy resource commodities in the Pedirka/western Eromanga basins region targeting conventional and unconventional hydrocarbons as well as evaluating the suitability of sedimentary sections to store carbon dioxide.</div><div>The interpretation of new biostratigraphic and reprocessed seismic data provided new insights into the regional geology of this previously explored region. The Permian, Triassic and Jurassic depositional history of the study area is largely recorded by extensive fluvial-lacustrine sediments, including changes from braided to meandering river systems and sustained periods of flood-plain environments in which thick sequences of coal-bearing strata developed. During the Cretaceous, expanding shallow marine environments were established in the western part of the Pedirka/western Eromanga region.</div><div>Age-control obtained from palynological analysis and the mapping of key seismic horizons yielded an improved understanding of the extent and character of unconformities which define breaks and changes in depositional processes. Results from new regional stratigraphic correlations initiated a comprehensive review of previously established basin definitions in the greater Pedirka/western Eromanga area. </div><div>While confirming the stacked nature of these basins which hold sedimentary records from the early Paleozoic to the Late Cretaceous, changes to stratigraphic basin boundaries have been applied to more correctly reflect the impact of unconformity related depositional breaks. As a result, the Lower and Middle Triassic Walkandi Formation is now assigned to the upper section of the Pedirka Basin, while the Upper Triassic Peera Peera Formation represents commencement of deposition in the western Eromanga Basin, thereby abandoning the recognition of the Simpson Basin as a separate Triassic depocenter. </div><div><br></div><div><br></div>
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<div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future (EFTF) program, which commenced in 2016, is an eight year, $225m investment by the Australian Government. </div><div><br></div><div>As part of the EFTF Program, Geoscience has completed a multi-disciplinary study to investigate the energy resource potential of selected onshore basins within central Australia under the Australia’s Future Energy Resources (AFER) Project. The AFER Project has adapted the conventional hydrocarbon play-based exploration workflow, developed by the petroleum industry over several decades, to develop a similar approach for assessing unconventional hydrocarbon resource potential and CO2 geological storage prospectivity. Play-based exploration is a method of building and leveraging an understanding of a basin and its sediment-hosted resources by systematically evaluating a series of play intervals using the best available geological data and models. Each play interval represents a regionally significant reservoir/aquifer for one or more resources (e.g. hydrocarbons, groundwater, CO2 storage intervals) often with an associated seal/aquitard. Various ‘risk elements’ that are essential for a resource to exist can be mapped and qualified with a probability of geological success. These risk elements are then spatially integrated (stacked) to generate common risk segment (CRS) or ‘heat’ maps for each play interval that indicate areas of relatively high prospectivity versus relatively low prospectivity. Geological risk elements are evaluated using post-drill analysis of well control points, and geological maps generated from basin studies.</div><div><br></div><div>Common risk segment mapping, supported by post-drill analysis, has been undertaken by the AFER Project using the GIS-Pax Player Software, and assigned a geological probability of success (POS) using a ‘split risking’ system that involves assessing: </div><div>· Pg play, which is the POS that the risk element is effective somewhere within the map segment; </div><div>· Pg repeatability, which is the POS of future repeated effective discoveries for the risk element within the map segment (i.e. the inherent variability or heterogeneity of the risk element); and the </div><div>· Pg overall (Pg play x Pg repeatability). </div><div><br></div><div>This data package provides a spatial data set (CRS maps and post-drill analysis) capturing the AFER project’s assessment of hydrocarbon resources (conventional hydrocarbons, coal seam gas, and shale hydrocarbons) and the CO2 geological storage potential of the Pedirka and western Eromanga basins. The data package includes the following data sets:</div><div>1. Common risk segment maps for conventional hydrocarbons, unconventional hydrocarbons and CO2 geological storage resources provided in ESRI© ArcGIS file geodatabase format (gdb).</div><div>2. Common risk segment maps for conventional hydrocarbons, unconventional hydrocarbons and CO2 geological storage resources provided in ESRI© shape format (shp).</div><div>3. Post-drill analysis data provided in ESRI© shape format (shp).</div><div>4. Metadata forms documenting key information (abstract, data sources, lineage for related groups of map layers, keywords) for each group of related CRS maps and for the post-drill analysis results. </div><div><br></div><div>The product authors wish to acknowledge Tehani Palu (Geoscience Australia) for her internal peer review of the digital data package, Darren Ferdinando (Basin Science Pty Ltd) for his review of the conventional hydrocarbon common risk segment mapping, and Catherine Flowers (Geoscience Australia) for her technical support in developing the GIS products.</div><div><br></div><div><br></div>
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<div>The Permian Pedirka, the Triassic Simpson and the Jurassic–Cretaceous western Eromanga basins in central Australia have undergone a sporadic exploration history which commenced in the 1950s. Exploration initially focused on conventional hydrocarbons from the 1950s–1980s, before shifting towards coal seam gas (CSG) opportunities in the 2000s. The basins remain underexplored with only 42 wells drilled, and ~16,000 line km of 2D seismic acquired across a study area of ~210,000 km2. An active petroleum system has been proven by a non-commercial oil discovery at Poolowanna 1, as well as by several wells that show evidence of residual oil columns. However, sparse and low-quality seismic data make it challenging to map and identify new energy resource opportunities. Geoscience Australia, the Northern Territory Geological Survey, and the South Australian Department for Energy and Mining are collaborating on the Australia’s Future Energy Resources (AFER) project to undertake an assessment of the resource potential for conventional and unconventional hydrocarbons and the carbon capture and storage (CCS) potential in the Pedirka, Simpson and western Eromanga basins. The project’s objective is to produce spatially-enabled and risked resource estimates to provide government and industry stakeholders with decision making tools to address the region’s energy resources and CCS potential. Post-drill analysis is a key component of evaluating the resource potential of a region by ensuring that a systematic, data-driven approach is used to evaluate discrete exploration play intervals and trapping mechanisms. The study area has been divided into 16 chronostratigraphic play intervals and post-drill analysis has been undertaken to evaluate the presence and effectiveness of the main conventional petroleum systems play elements of reservoir, seal, trap and hydrocarbon charge. The post-drill analysis methodology to assess conventional hydrocarbons has also been modified to assess the geological elements that are essential to evaluate unconventional petroleum resources and CCS potential within the study area. The qualitative results indicate conventional hydrocarbon, CCS, CSG and shale hydrocarbon opportunities across multiple plays, highlighting that an area that has been primarily explored for one resource type in the past may have other opportunities for industry to evaluate. This Abstract was submitted/presented to the 2022 Central Australian Basins Symposium IV (CABS) 29-30 August (https://agentur.eventsair.com/cabsiv/)
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<diThe Permian and Triassic Pedirka and Simpson basins in central Australia have proven petroleum potential with a non-commercial oil discovery in the Poolowanna Trough and several wells showing evidence for residual oil columns. However, these basins remain underexplored with only 42 wells drilled and relatively sparse 2D seismic coverage. Consequently, our knowledge of the structural and stratigraphic framework of the basins continues to grow as new data sets are acquired. Understanding the area’s resource potential continues to improve as new insights are gained into the presence and effectiveness of the main risk elements (reservoir, seal, hydrocarbon charge and trapping mechanisms) associated with a variety of sub-surface resources. Geoscience Australia, the Northern Territory Geological Survey, and the South Australian Department of Energy and Mining are collaborating on the Australia’s Future Energy Resources project under the Exploring for the Future program. One of the aims of this collaborative project is to assess the resource potential for conventional and unconventional hydrocarbons and carbon capture and storage (CCS) resources in the Pedirka, Simpson and western Eromanga basins. A play-based exploration approach is being used to systematically evaluate the key risk elements for each regional reservoir-seal interval (i.e. (play intervals) through the analysis of drilling results and spatial data to map sweet spots. These assessments aim to reduce exploration uncertainties by providing spatially-enabled assessments of the energy resources and CCS potential of the region. A key requirement for undertaking play-based resource assessments is to develop a chronostratigraphic geological framework that defines the main regional play intervals. Regional play schemes have been developed and applied over several decades for petroleum explorers in Western Australia, but have not yet become readily available for explorers in central and eastern Australian onshore basins. This paper presents a chronostratigraphic play scheme that is being applied to resource assessments in the Pedirka and Simpson basins. The scheme includes two Triassic play intervals correlating to the Peera Peera and Walkandi formations, and three Permian play intervals correlating to the Purni Formation and the Crown Point Formation. This Abstract was submitted/presented to the 2022 Central Australian Basins Symposium IV (CABS) 29-30 August (https://agentur.eventsair.com/cabsiv/)
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Geoscience Australia commissioned reprocessing of selected legacy 2D seismic data in the Pedirka-Simpson Basin in South Australia-Northern Territory as part of the Exploring for the Future (EFTF) program. 34 Legacy 2D seismic lines from the Pedirka Basin were reprocessed between May 2021 and January 2022 (phase 1). An additional 54 legacy 2D seismic lines (34 lines from Pedirka Basin, South Australia and 20 lines from Simpson Basin, Northern Territory) were reprocessed between November 2021 and June 2022 (phase 2). Geofizyka Toruń S.A. based in Poland carried out the data processing and Geoscience Australia with the help of an external contractor undertook the quality control of the data processing. The seismic data release package contains reprocessed seismic data acquired between 1974 and 2008. In total, the package contains approximately 3,806.9 km of industry 2D reflection seismic data. The seismic surveys include the Beal Hill, 1974; Pilan Hill, 1976; Koomarinna, 1980; Christmas Creek, 1982; Hogarth, 1984; Morphett, 1984; Colson 2D, 1985; Etingimbra, 1985; Fletcher, 1986; Anacoora, 1987; Mitchell, 1987; Bejah, 1987; Simpson Desert, 1979, 1984, 1986, 1987; Forrest, 1988; Eringa Trough, 1994; Amadeus-Pedirka, 2008 and covers areas within the Amadeus Basin, Simpson Basin, Pedirka Basin, Warburton Basin and Cooper Basin in South Australia and Northern Territory. The objective of the seismic reprocessing was to produce a processed 2D land seismic reflection dataset using the latest processing techniques to improve resolution and data quality over legacy processing. In particular, the purpose of the reprocessing was to image the structure and stratigraphic architecture of the Neoproterozoic to Late Palaeozoic Amadeus Basin, Triassic Simpson Basin, Cambrian–Devonian Warburton Basin, Permian–Triassic Pedirka Basin and Cooper Basin. All vintages were processed to DMO stack, Pre-stack Time Migration and Post-Stack Time Migration. <b>Data is available on request from clientservices@ga.gov.au - Quote eCat# 146309</b>
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<div>Understanding the hydrocarbon potential of Australia’s sedimentary basins is critical to ensuring the nation’s future energy security. The Pedirka and western Eromanga basins have proven petroleum potential with a sub-commercial oil discovery at Poolowanna 1 in the Poolowanna Trough and several wells drilled over the Colson Shelf and Madigan Trough showing evidence for residual oil zones. However, these basins remain relatively underexplored with only 42 petroleum wells drilled and relatively sparse 2D seismic data coverage. Geoscience Australia’s AFER Project has undertaken a qualitative and quantitative play-based assessment of the Pedirka and western Eromanga basins to enable a better understanding of their undiscovered hydrocarbon resources.</div><div><br></div><div>The AFER Project’s assessments are underpinned by new geological insights into the western Eromanga Basin and a supporting upscaled 3D geological model. A play-based common risk segment (CRS) mapping approach has been applied to eleven play intervals to delineate basin areas with relatively high prospectivity based on five geological risk elements: reservoir presence, reservoir effectiveness, top seal, trap presence, and hydrocarbon charge. Results from this qualitative component of the assessment indicate that the highest potential for future hydrocarbon discoveries is likely to be conventional oil resources across the Poolowanna Trough, Colson Shelf and Madigan Trough. The most prospective exploration targets are the Namur-Murta, Poolowanna and Peera Peera play intervals on a geological probability of success basis. The Peera Peera and Poolowanna play intervals have proven hydrocarbon charge from the Poolowanna 1 oil discovery but show poor reservoir quality (porosity <10%) in wells drilled across the Poolowanna Trough. These play intervals likely represent tight conventional oil exploration targets across their main play fairways in the Poolowanna Trough. The Namur-Murta interval has high reservoir qualities across all potentially prospective areas but has lower certainty regarding hydrocarbon charge with the most significant exploration result to date being a residual oil zone in the Madigan Trough. Moderate to high prospectivity for conventional oil is interpreted to occur in the Adori-Westbourne, Birkhead and Hutton play intervals over the eastern flanks of the Poolowanna Trough and western flanks of the Birdsville Track Ridge. The Walkandi, Upper Purni, Lower Purni and Crown Point play intervals are assessed as having moderate prospectivity for conventional oil over the Eringa Trough, Madigan Trough and Colson Shelf. </div><div><br></div><div>A quantitative assessment of the ‘Yet to Find’ hydrocarbon volumes has been undertaken to provide a play-level indication of the possible undiscovered conventional oil volumes. The risked volumes include a ‘Base Case’ that reflects the current exploration understanding of the basins, and a ‘High Case’ that reflects the potential impact of a new working petroleum system being discovered in the basins. The mean risked recoverable oil volume for the Base Case scenario total 22.2 MMbbl for the four plays evaluated (Namur-Murta, Poolowanna, Peera Peera and Lower Purni). About 70% of the risked mean volumes occur in the Poolowanna and Namur-Murta play intervals. Results from the High Case model highlight the significantly greater YTF potential across the basins if the geological requirement for a new working petroleum system eventuates from further exploration, with a total mean risked volume of 234.8 MMbbl for the three play intervals evaluated (Namur-Murta, Poolowanna and Lower Purni). Risked volumes are relatively evenly distributed across the three play intervals. </div><div><br></div><div>Unconventional hydrocarbons are evaluated as being less prospective than conventional hydrocarbons in the western Eromanga basin. Shale oil plays have not previously been explored but may be present within organic-rich shales from the Poolowanna and Peera Peera play intervals. These shale oil plays are evaluated as being moderately prospectivity due to their thin and heterogeneous character. Coal seam gas (CSG) wells drilled into the Upper Purni and Lower Purni play intervals have to date only demonstrated the presence of gas-undersaturated coal seams over the Andado Shelf. However, CSG is the most likely hydrocarbon resource type to produce hydrocarbons from the Pedirka Basin if future exploration can identify sweet spots where different geological conditions occur that are conducive to preserving high gas saturations. </div><div><br></div>
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<div>This Record presents data collected as part of the ongoing Northern Territory Geological Survey–Geoscience Australia SHRIMP geochronology project under the National Collaboration Framework agreement. New U-Pb SHRIMP zircon geochronological results were derived from six samples of sedimentary rocks collected from two petroleum exploration drillholes (CBM 107-001 and CBM 107-002) that intersect the Pedirka Basin in the southeastern corner of the Northern Territory.</div><div><br></div><div>Geologically, this is a region in the Simpson Desert that encompasses several superimposed intracratonic sedimentary basins, which are separated by regional unconformities extending over areas of adjoining Queensland, South Australia and New South Wales. In the southeastern corner of the Northern Territory, the Pedirka Basin is one of three stacked basins. The exposed Mesozoic Eromanga Basin overlies the late Palaeozoic to Triassic Pedirka Basin, which is largely restricted to the subsurface, and in turn overlies the Palaeozoic pericratonic Warburton Basin (Munson and Ahmad 2013).</div><div><br></div><div>As the Pedirka Basin is almost entirely concealed beneath the Eromanga Basin, our current understanding of the geology in this southeastern corner of the Northern Territory is constrained by a limited number of exploration drillholes and 2D seismic coverage (Doig 2022). The samples described herein were collected to aid in defining the chronostratigraphy and sedimentary provenance characteristics of the Pedirka Basin.</div><div><br></div><div>BIBLIOGRAPHIC REFERENCE: Jones S.L., Jarrett A.J., Verdel C.S. and Bodorkos S. 2024. Summary of results. Joint NTGS–GA geochronology project: Pedirka Basin. Northern Territory Geological Survey, Record 2024-003.</div>
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<div>Palynology preparations from 50 samples from several key wells in the South Australian section of the Pedirka Basin were examined for Geoscience Australia. The sampling was done by Carey Hannaford under inspection number 5358 (see table 1 for sample listing). All resulting slides and remaining residue have been submitted to government. The samples were analysed quantitatively with the first 200 specimens in each sample counted and subsequent species simply recorded as present. In this summary report, the results are provided in tabulated form only. Details of the palynomorph assemblages are recorded on StrataBugs distribution charts, with each taxon expressed as a percentage of the entire assemblage (Appendix B). From this information, assignments are made to the palynostratigraphic scheme of Price (1997), as shown in Figures 1 and 2 and summarised in Appendix A.</div><div>Wells included are: Erabena-1, Macumba-1, Mokari-1, Oolarinna-1, Pandieburra-1, Poolowanna-1, Poolowanna-2, Walkandi-1. </div><div>Also see accompanying report by Hannaford and Mantle, 2022: Palynological analysis of infill samples for selected wells in the Northern Territory section of the Pedirka Basin.</div>