The Canning Basin is a large intracratonic basin in Western Australia that remains one of the least explored Paleozoic basins in the world. Recent resource assessments have renewed interest in the basin, in particular for unconventional gas within Ordovician organic-rich shales, although these proposed plays remain untested. Exploring for the Future (EFTF) is a program dedicated to exploring Australia’s resource potential and boosting investment. Launched in 2016 with $100.5 million in funding from the Australian Government, it initially focused on northern Australia. Geoscience Australia and the Geological Survey of Western Australia collected new, pre-competitive datasets in the frontier Kidson Sub-basin to better understand its energy resource potential. Here we present an overview of the regional petroleum systems with a focus on the modelled Ordovician section within the Kidson Sub-basin and Barnicarndy Graben (previously Waukarlycarly Embayment). Three Larapintine petroleum systems are recognised in the Ordovician (L2), Devonian‒earliest Carboniferous (L3), and Carboniferous (L4) successions of the Canning Basin. Integration of petroleum systems with interpretation of the Kidson Sub-basin seismic survey 18GA-KB1 shows that the Ordovician section is extensive, and hence, the Larapintine 2 Petroleum System is of most exploration interest across this frontier region. Ordovician organic-rich units are known within the Nambeet (Tremadocian–Floian), Goldwyer (Dapingian–Darriwilian) and Bongabinni (Sandbian) formations; however, only Nambeet and Goldwyer source rocks are considered to be present within the Kidson Sub-basin. Oil and gas shows occur within Ordovician and Silurian reservoirs, of which many are sub-salt. The range in the geochemical profile of shows from Goldwyer, Nita and Sahara reservoirs implies generation from numerous source units within the Goldwyer and Bongabinni formations. The origin of oil and gas shows within the Nambeet and Willara formations, including those in Patience 2 in the Kidson Sub-basin, is unknown but imply the presence of multiple lower Ordovician source units and include the Nambeet Formation. Within the Kidson Sub-basin, Kidson 1 is located closest to the main depocentre, whereas other wells are proximal to shelves and margins. In general, these latter wells return discouraging hydrocarbon potential pyrolysis parameters as a consequence of their sub-optimal location for source rock development and thermal maturation history. Kidson 1 penetrates the Goldwyer Formation and has TOC contents that are considered more representative of source rock richness (although diesel contamination is present) within the depocentre. Data paucity is the key limitation in resource evaluation for the Kidson Sub-basin, as such, an evaluation with volumetrics is not possible. 1D petroleum systems models of ten wells located in either the Kidson Sub-basin, Willara Sub-basin or Barnicarndy Graben were constructed to resolve whether potential source rocks were capable of hydrocarbon generation. The models demonstrate maturation of Ordovician source rocks resulting in near-complete transformation during Permian to Triassic deposition and burial. A 2D petroleum systems model constructed along the regional 2D seismic line 18GA-KB1 predicts full maturation of Larapintine 2 source rocks in the deeper parts of the Kidson Sub-basin. Expulsion and migration is considered to have taken place during the Permian‒Triassic, with potential accumulations trapped by evaporitic and fine-grained units of Ordovician and Silurian age.

This report presents the results of an elemental and carbon and oxygen isotope chemostratigraphy study on three historic wells; Kidson-1, Willara-1 and Samphire Marsh-1, from the southern Canning Basin, Western Australia. The objective of this study was to correlate the Early to Middle Ordovician sections of the three wells to each other and to wells with existing elemental and carbonate carbon isotope chemostratigraphy data from the Broome Platform, Kidson and Willara sub-basins, and the recently drilled and fully cored stratigraphic Waukarlycarly 1 well from the Waukarlycarly Embayment.

The onshore Canning Basin in Western Australia is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the Exploring for the Future (EFTF) program; an Australian Government initiative dedicated to increasing investment in resource exploration in northern Australia. The four-year program led by Geoscience Australia focusses on the acquisition of new data and information about the potential mineral, energy and groundwater resources concealed beneath the surface in northern Australia and parts of South Australia. As part of this program, significant work has been carried out to deliver new pre-competitive data including new seismic acquisition, drilling of a stratigraphic well, and the geochemical analysis of geological samples recovered from exploration wells. A regional, 872 km long 2D seismic line (18GA-KB1) acquired in 2018 by Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA), images the Kidson Sub-basin of the Canning Basin. In order to provide a test of geological interpretations made from the Kidson seismic survey, a deep stratigraphic well, Waukarlycarly 1, was drilled in 2019 in partnership between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA) in the South West Canning Basin. The Waukarlycarly 1 stratigraphic well was drilled in the Waukarlycarly Embayment, 67 km west of Telfer and provides stratigraphic control for the geology imaged by the Kidson seismic line (Figure 1). The well was drilled to a total drillers depth (TD) of 2680.53 mRT and penetrated a thin Cenozoic cover overlying a Permian fluvial clastic succession that includes glacial diamictite. These siliciclastics unconformably overlie an extremely thick (>1730 m) interpreted Ordovician succession before terminating in low-grade metasediments of Neoproterozoic age. Log characterisation, core analysis, geochronology, petrographic and palaeontological studies have been carried out to characterise the lithology, age and depositional environment of these sediments. As part of this comprehensive analytical program, magnetic susceptibility and bulk density analyses were undertaken by Geoscience Australia on selected rock samples.

Laboratory results for fluid inclusion gas analysis in GA's Isotope and Organic Geochemistry Laboratory under GSWA Approval G004119

The Ordovician is an important period in Earth’s history with exceptionally high sea levels that facilitated the Great Ordovician Biodiversification Event. This crucial biological event is regarded as the second most significant evolutionary event in the history of Paleozoic life, after the Cambrian radiation. The present study integrates palynological, petrographic, molecular and stable isotopic (δ13C of biomarkers) analyses of cores from five boreholes that intersected the Goldwyer Formation, Canning Basin, Western Australia, to determine depositional environments and microbial diversity within a Middle Ordovician epicontinental, tropical sea. A major transgression was detected in the laminated shales of the lower Goldwyer Formation (Units 1+2) which were deposited in anoxic bottom waters, as confirmed by low (<1) Pristane/Phytane ratios, and elevated dibenzothiophene and gammacerane indices. A second, less extensive, flooding event is recorded by shallow marine sediments of the upper Goldwyer Formation (Unit 4). Cores of these sediments, from two wells (Solanum-1 and Santalum-1A) are bioturbated and biomarkers indicate relatively oxygenated conditions, as well as the presence of methanotrophic bacteria, as determined from the high 3-methylhopane indices. Typical Ordovician marine organisms including acritarchs, chitinozoans, conodonts and graptolites were present in the lower and upper Goldwyer Formation, whereas the enigmatic organism Gloeocapsomorpha prisca (G. prisca) was only detected in Unit 4. The presence of G. prisca was based on microfossils and specific biosignatures presenting an odd-over-even predominance in the C15 to C19 n-alkane range. Cryptospores were identified in Unit 4 in the Theia-1 well and are most likely derived from bryophytes, making this is the oldest record of land plants in Australian Middle Ordovician strata. Biomarkers in some samples from Unit 4 that also support derivation from terrestrial organic matter include retene, benzonaphthofurans and δ13C-depleted mid-chain n-alkanes. This research contributes to understanding Ordovician marine environments from a molecular perspective since few biomarker studies have been undertaken on age-equivalent sections. Furthermore, the identification of the oldest cryptospores in Australia and their corresponding terrestrial biomarkers contributes to understanding the geographical evolution of early land plants.

A key challenge in exploring Australian onshore sedimentary basins is limited seismic data coverage. Consequently, well logs are often the main datasets that can be used to understand the subsurface geology. The primary aim of this study was to develop a methodology for visualising the three-dimensional (3D) tectonostratigraphic architecture of sedimentary basins using well data, which can then be used to quickly screen areas warranting more detailed studies of resource potential. This project has developed a workflow that generates 3D well correlations using sequence stratigraphic well tops to visualise the regional structural and stratigraphic architecture of the Amadeus, Canning, Officer and Georgina basins in the Centralian Superbasin. Thirteen Neoproterozoic‒Paleozoic supersequence tops were interpreted in 134 wells. Three-dimensional well correlations provide an effective regional visualisation of the tectonostratigraphic architecture across the main depocentres. This study redefines the Centralian Superbasin as encompassing all western, northern and central Australian basins that had episodically interconnected depositional systems driven by regional subsidence during one or more regional tectonic events between the Neoproterozoic and middle Carboniferous. The Centralian Superbasin began to form during Neoproterozoic extension, and underwent several phases of partial or complete disconnection and subsequent reconnection of depositional systems during various regional tectonic events before final separation of depocentres at the culmination of the Alice Springs Orogeny. Regional 3D correlation diagrams have been generated to show the spatial distribution of these supersequences, which can be used to visualise the distribution of stratigraphic elements associated with petroleum, mineral and groundwater systems. <b>Citation: </b>Bradshaw, B., Khider, K., MacFarlane, S., Rollet, N., Carr, L. and Henson, P., 2020. Tectonostratigraphic evolution of the Centralian Superbasin (Australia) revealed by three-dimensional well correlations. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

Exploring for the Future (EFTF) is an Australian Government initiative focused on gathering new data and information about potential mineral, energy and groundwater resources across northern Australia. This area is generally under-explored and offers enormous potential for industry development, as it is advantageously located close to major global markets, infrastructure and hosts many prospective regions. In June 2020, the Hon Keith Pitt MP, Minister for Resources, Water and Northern Australia, announced a four year extension to this program with an expansion in scope to cover the whole of Australia. The energy component of EFTF aims to improve our understanding of the petroleum potential of frontier Australian basins. Building an understanding of geomechanical rock properties is key to understanding both conventional and unconventional petroleum systems as well as carbon storage and sedimentary geothermal systems. Under EFTF, Geoscience Australia has undertaken geomechanical work including stress modelling, shale brittleness studies, and the acquisition of new rock property data through extensive testing on samples from the Paleo- to Mesoproterozoic South Nicholson region of Queensland and the Northern Territory and the Paleozoic Kidson Sub-basin of Western Australia. These analyses are summarised herein. Providing baseline geomechanical data in frontier basins is essential as legacy data coverage can often be inadequate for making investment decisions, particularly where unconventional plays are a primary exploration target. As EFTF increases in scope, Geoscience Australia anticipates expanding these studies to encompass further underexplored regions throughout Australia, lowering the barrier to entry and encouraging greenfield exploration. <b>Citation:</b> Bailey Adam H. E., Jarrett Amber J. M., Wang Liuqi, Dewhurst David N., Esteban Lionel, Kager Shane, Monmusson Ludwig, Carr Lidena K., Henson Paul A. (2021) Exploring for the Future geomechanics: breaking down barriers to exploration. <i>The APPEA Journal </i><b>61</b>, 579-587. https://doi.org/10.1071/AJ20039

<p>The Paleozoic Canning Basin is a large (~720 000 km2) frontier province with several proven petroleum systems. Recent oil production from the Ungani field on the southern edge of the Fitzroy Trough has boosted the small-scale production of crude oil and gas discovered in the 1980s on the Lennard Shelf and flanking terraces (e.g. Blina, Boundary, Lloyd, Sundown, West Kora, West Terrace). Determining the paleo-depositional environments within the epicontinental seaway is essential to characterise source rock formation and distribution, and hence assist future exploration strategies.</p> <p>This study of diagnostic biomarker hydrocarbons derived from the coloured carotenoid pigments of photosynthetic organisms (including plants, algae, cyanobacteria and photosynthetic bacteria) was designed to extend the geochemistry of the Ordovician-, Middle to Late Devonian- and Early Carboniferous-sourced oils of the basin published by Edwards et al. (2013) and Spaak et al. (2017, 2018), and implemented by GeoMark Research. The focus was to clarify the paleo-depositional environment of their marine source rocks and the extent of water stratification, and to expand upon the diversity of the contributing organic matter. The oils on the Lennard Shelf and those on the southern side of the Fitzroy Trough (e.g. Ungani and Dodonea 1) preserve a diverse range of biomarkers, including both saturated and aromatic C40 carotenoid-derived compounds (Figure 1) due to minimal secondary alteration. All analysed oils contain the saturated biomarker beta-carotane, derived from algae and cyanobacteria that flourish in sunlit oxygenated water. In addition, the oils also contain aromatic carotenoids produced by photosynthetic green sulphur bacteria, which inhabit the photic zone of euxinic water columns (e.g. Summons & Powell, 1986; French et al., 2015). Paleorenieratane is the dominant C40 aromatic carotenoid in the Ordovician (Dodonea 1, Pictor) and Late Devonian-sourced oils (Blina 1, 2, 4 and Janpam North 1; Figure 1). Oils on the Lennard Shelf generated by Lower Carboniferous source rocks have variable distributions of carotenoids with isorenieratane either in similar concentration to paleorenieratane (Point Torment 1, Sundown 2), absent (West Kora 1) or, in the case of Terrace 1, in lower abundance relative to paleorenieratane. Paleorenieratane, isorenieratane and renieratane are absent in oils from Wattle 1 ST1 and Mirbelia 1. Chlorobactane, also derived from green sulphur bacteria, is present in many of the analysed oils (and is the dominant peak in Point Torment 1), whereas okenane (derived from purple sulphur bacteria) was not detected. The exception is the Late Ordovician (Sandbian) Cudalgarra 1 oil that contains a low concentration of okenane, and in which isorenieratane predominates over paleorenieratane. The aromatic carotenoid distribution in oil from Ungani 2 is similar to those from both Terrace 1 and Blina (Figure 1).</p> <p>The association of these saturated and aromatic carotenoids in Paleozoic Canning Basin oils provides evidence for long-term restricted circulation and the development of shallow chemoclines in an epicontinental seaway centred along the Fitzroy Trough and Gregory Sub-basin in which oxygenated surface water frequently overlaid deeper, anoxic, sulphidic (euxinic) water also within the photic zone.</p> <p>REFERENCES Edwards, D.S., Boreham, C.J., Chen, J., Grosjean, E., Mory, A.J., Sohn, J., Zumberge, J.E., 2013. Stable carbon and hydrogen isotopic compositions of Paleozoic marine crude oils from the Canning Basin: comparison with other west Australian crude oils. In: Keep, M., Moss, S. (Editors), The Sedimentary Basins of Western Australia IV, Perth, WA. Edwards, P., Streitberg, E., 2013. Have we deciphered the Canning? Discovery of the Ungani oil field. In: Keep, M., Moss, S. (Editors), The Sedimentary Basins of Western Australia IV, Perth, WA. French, K.L., Rocher, D., Zumberge, J.E., Summons, R.E., 2015. Assessing the distribution of sedimentary C40 carotenoids through time. Geobiology 13, 139–151, 10.1111/gbi.12126. Spaak, G., Edwards, D.S., Allen, H.J., Grotheer, H., Summons, R.E., Coolen, M.J.L., Grice, K., 2018. Extent and persistence of photic zone euxinia in Middle–Late Devonian seas – insights from the Canning Basin and implications for petroleum source rock formation. Marine and Petroleum Geology, 93, 33–56. Spaak, G., Edwards, D.S., Foster, C.B., Pagès, A., Summons, R.E., Sherwood, N., Grice, K., 2017. Environmental conditions and microbial community structure during the Great Ordovician Biodiversification Event; a multi-disciplinary study from the Canning Basin, Western Australia. Global and Planetary Change, 159, 93–112. Summons, R.E., Powell, T.G., 1986. Chlorobiaceae in Palaeozoic seas revealed by biological markers, isotopes and geology. Nature 319, 763–765.</p>

<p>The Early Paleozoic, specifically the Middle Ordovician, marks a significant period in Earth's history due to the appearance and diversification of life on land. Plant megafossil records indicate vascular plants first appeared in the Early Silurian and by Devonian times had diversified rapidly (e.g. Wellman and Gray, 2000; Steemans et al., 2009; Kenrick et al., 2012; Strother, 2016). However non-vascular plants (bryophytes) predating vascular plants are rarely preserved as body fossils and the bryophyte microfossil record in the lowermost Palaeozoic is scarce. This lack of fossil data severely limits our understanding of life in the earliest non-marine environments and the origin of land plants. <p>In comparison to microfossils, molecular fossils (biomarkers) are more ubiquitous in the sedimentary record and have a higher preservation potential, thus providing a powerful tool to track terrestrial signals when microfossils are either scarce or absent. Molecular proxies such as long chain n-alkanes have been used extensively in both modern and ancient environments to identify terrestrial contributions to the organic matter (e.g. Eglinton and Hamilton, 1967; Ficken et al., 2000; Hautevelle et al., 2006). Furthermore, the isotopic composition of these molecules can be used to further distinguish between sources (e.g. Bird et al., 1995; Sikes et al., 2009; Rouillard et al., 2016). That being said, only relatively few studies have combined palynological evidence with geochemical proxies to assess geochemical signatures of early land plants. <p>This work presents biomarker and palynological data of the Middle Ordovicianupper Goldwyer Formation which records the earliest occurrence of land plant microfossils (cryptospores) in Australia. The higher-molecular-weight n-alkane distributions and their isotopic compositions recorded in the upper Goldwyer show high resemblances to modern day bryophytes and aquatic macrophytes. Retene, a biomarker conventionally used as a proxy for gymnosperms, was also identified in some extracts. The presence of retene in Middle Ordovician (this work) and Silurian (Romero-Sarmiento et al., 2010) rocks indicates conifers are not the sole source of this compound. <p>Linking biomarkers and palynology has shown to beuseful in the study of early land plants where fossil records are sparse. Molecular and isotopic proxies distinctive of these plants can provide a more complete record of the geographical distribution of early land plants, providing useful information to understand their early evolution. <p>Bird, M.I., Summons, R.E., Gagan, M.K., Roksandic, Z., Dowling, L., Head, J., Fifield, L.K., Cresswell, R.G., Johnson, D.P., 1995. Terrestrial vegetation change inferred from n-alkane δ13C analysis in the marine environment. Geochimica et Cosmochimica Acta 59, 2853-2857. <p>Eglinton, G., Hamilton, R.J., 1967. Leaf epicuticular waxes. Science 156, 1322-1335. <p>Ficken, K.J., Li, B., Swain, D.L., Eglinton, G., 2000. An n-alkane proxy for the sedimentary input of submerged/floating freshwater aquatic macrophytes. Organic Geochemistry 31, 745-749. <p>Hautevelle, Y., Michels, R., Malartre, F., Trouiller, A., 2006. Vascular plant biomarkers as proxies for palaeoflora and palaeoclimatic changes at the Dogger/Malm transition of the Paris Basin (France). Organic Geochemistry 37, 610-625. <p>Kenrick, P., Wellman, C.H., Schneider, H., Edgecombe, G.D., 2012. A timeline for terrestrialization : consequences for the carbon cycle in the Palaeozoic. Philosophical Transactions of the Royal Society B: Biological Sciences 367, 519-536. <p>Romero-Sarmiento, M.F., Riboulleau, A., Vecoli, M., Versteegh, G.J.M., 2010. Occurrence of retene in upper Silurian-lower Devonian sediments from North Africa: origin and implications. Organic Geochemistry 41, 302-306. <p>Rouillard, A., Greenwood, P.F., Grice, K., Skrzypek, G., Dogramaci, S., Turney, C., Grierson, P.F., 2016. Interpreting vegetation change in tropical arid ecosystems from sediment molecular fossils and their stable isotope compositions: a baseline study from the Pilbara region of northwest Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 459, 495-507. <p>Sikes, E.L., Uhle, M.E., Nodder, S.D., Howard, M.E., 2009. Sources of organic matter in a coastal marine environment: Evidence from n-alkanes and their delta13C distributions in the Hauraki Gulf, New Zealand. Marine Chemistry 113, 149-163. <p>Steemans, P., Herisse, A. Le, Melvin, J., Miller, M. a, Paris, F., Verniers, J., Wellman, C.H., 2009. Origin and radiation of the earliest vascular land plants. Science (New York, N.Y.) 324, 353. <p>Strother, P.K., 2016. Systematics and evolutionary significance of some new cryptospores from the Cambrian of eastern Tennessee, USA. Review of Palaeobotany and Palynology 227, 28-41. <p>Wellman, C.H., Gray, J., 2000. The microfossil record of early land plants. Philosophical Transactions of the Royal Society B: Biological Sciences 355, 717-732.

Exploring for the Future (EFTF) is an Australian Government initiative that gathers new data and information about potential mineral, energy and groundwater resources. Commencing in 2016 with a focus on northern Australia, an EFTF extension to 2024 was recently announced, with expanded coverage across mainland Australia and Tasmania. The EFTF energy component aims to improve our understanding of the petroleum potential of frontier onshore Australian basins and has acquired significant pre-competitive datasets, including the recently drilled Barnicarndy 1 deep stratigraphic well in Western Australia’s Canning Basin (in partnership with the Geological Survey of Western Australia), and NDI Carrara 1 deep stratigraphic well in the South Nicholson region of the Northern Territory (in partnership with the MinEX CRC). These are the first stratigraphic wells drilled in a petroleum basin by Geoscience Australia since the formation in 2001 from its predecessor agencies. Both wells were sited along two-dimensional, deep crustal seismic surveys acquired by Geoscience Australia as part of EFTF, and provide stratigraphic control for the imaged geology. The sedimentary fill intersected by the Barnicarndy 1 and NDI Carrara 1 wells were cored and logged with a broad suite of wireline tools, providing substantial new data in two frontier basins. These data provide insights into regional stratigraphy and local lithology. Geochronology, petrographic, organic and inorganic geochemistry, petrophysical rock properties, petroleum systems elements, palaeontological, and fluid inclusion studies have been undertaken upon which inferences on regional prospectivity can made in these data-poor regions. Moving into the next phase of EFTF, these wells provide a template for new pre-competitive data acquisition by Geoscience Australia, expanding our knowledge of frontier regions making them attractive for new investment and exploration.