The petroleum systems summary report provides a compilation of the current understanding of petroleum systems for the McArthur Basin, including the prospective Beetaloo Sub-basin. The contents of this report are also available via the Geoscience Australia Portal at https://portal.ga.gov.au/, called The Petroleum Systems Summary Assessment Tool (Edwards et al., 2020). Three summaries have been developed as part of the Exploring for the Future (EFTF) program (Czarnota et al., 2020); the McArthur Basin, the Canning Basin, and a combined summary of the South Nicholson Basin and Isa Superbasin region. The petroleum systems summary reports aim to facilitate exploration by summarising key datasets related to conventional and unconventional hydrocarbon exploration, enabling a quick, high-level assessment the hydrocarbon prospectivity of the region.

This petroleum systems summary report provides a compilation of the current understanding of petroleum systems for the South Nicholson Basin and Isa Superbasin region. The contents of this report are also available via the Geoscience Australia Portal at https://portal.ga.gov.au/, called The Petroleum Systems Summary Assessment Tool (Edwards et al., 2020). Three summaries have been developed as part of the Exploring for the Future (EFTF) program (Czarnota et al., 2020); the McArthur Basin, the Canning Basin, and a combined summary of the South Nicholson Basin and Isa Superbasin region. The petroleum systems summary reports aim to facilitate exploration by summarizing key datasets related to conventional and unconventional hydrocarbon exploration, enabling a quick, high-level assessment the hydrocarbon prospectivity of the region.

The unexpected discovery of oil in Triassic sedimentary rocks of the Phoenix South 1 well on Australia’s North West Shelf (NWS) has catalysed exploration interest in pre-Jurassic plays in the region. Subsequent neighbouring wells Roc 1–2, Phoenix South 2–3 and Dorado 1–3 drilled between 2015 and 2019 penetrated gas and/or oil columns, with the Dorado field containing one of the largest oil resources found in Australia in three decades. This study aims to understand the source of the oils and gases of the greater Phoenix area, Bedout Sub-basin using a multiparameter geochemical approach. Isotopic analyses combined with biomarker data confirm that these fluids represent a new Triassic petroleum system on the NWS unrelated to the Lower Triassic Hovea Member petroleum system of the Perth Basin. The Bedout Sub-basin fluids were generated from source rocks deposited in paralic environments with mixed type II/III kerogen, with lagoonal organofacies exhibiting excellent liquids potential. The Roc 1–2 gases and the Phoenix South 1 oil are likely sourced proximally by Lower–Middle Triassic TR10–TR15 sequences. Loss of gas within the Phoenix South 1 fluid due to potential trap breach has resulted in the formation of in-place oil. These discoveries are testament to new hydrocarbon plays within the Lower–Middle Triassic succession on the NWS.

This Geoscience Australia Record reports the findings of the Canning Basin Petroleum Systems Modelling Project. The southern, frontier portions of the Canning Basin have numerous potential hydrocarbon play opportunities, in particular unconventional gas plays, which remain untested. Of particular interest are Ordovician-aged petroleum systems. Geoscience Australia in collaboration with the Geological Survey of Western Australia acquired an 872 km long 2D seismic line across the south and south-west Canning Basin in 2018, and drilled the 2680 m stratigraphic hole Barnicarndy 1 in the Barnicarndy Graben to further develop the understanding of hydrocarbon prospectivity in these frontier regions. As part of the Exploring for the Future program Geoscience Australia contracted GNS Science to construct ten 1D petroleum systems models and one 2D model across the frontier southern parts of the basin. The aim was to combine interpretation of the newly acquired seismic data with interpretation of legacy and new well data, in particular organic geochemical data, to improve the understanding of the burial and thermal history, trap formation, generation and migration of hydrocarbons in the southern, frontier parts of the Canning Basin. This Record is a compilation of the work completed by GNS Science International Limited and the reports containing new data collected and analyzed relevant to the petroleum systems modelling.

The northern Lawn Hill Platform (nLHP) is considered an emerging region with less than 15 wells drilled to date. With renewed interest in unconventional gas, new exploration opportunities exist in this early Proterozoic region. Petroleum systems analysis is presented here to improve the understanding of burial history, source rock richness and maturity of the nLHP of the Isa Superbasin, far NW Queensland. A pseudo-3D geological model was built and calibrated, in combination with 1-D burial and thermal history modelling of Desert Creek 1 and Egilabria 1. These were combined with source rock characteristics (e.g., Rock Eval and kerogen kinetics) which helped assess the hydrocarbon generation potential by source rock, allowing a broader assessment of petroleum prospectivity of the nLHP. The study focussed on two potential source rocks; the Lawn 4 Sequence and the River Supersequence. Maturity modelling of the Lawn 4 Sequence at Desert Creek 1 and Egilabria 1 predicted equivalent vitrinite reflectance (EqVR) of over 1.2% and 2%, respectively. The River Supersequence was modelled as overmature at both wells. Combining these results with the pseudo-3D model and source rock characteristics demonstrates that the highest maturities are encountered in the deepest depocentres to the east and gradually decrease in maturity to the west, indicating some potential for wet gas. Modelling results show generation of varying amounts of gas and oil from each potential source rock. Overall, due to the age of the sediments, maximum depth of burial and high paleotemperatures, the most likely hydrocarbon phase is gas from primary generation and supplemented by secondary gas from oil cracking. In spite of high maturities, encouraging gas shows from the Egilabria prospect support continued exploration interest in this region for unconventional hydrocarbons.

This report highlights results of petroleum systems analysis undertaken on the northern Lawn Hill Platform area of the Isa Superbasin, specifically focusing on burial and thermal history modelling. A second report will highlight the results of the source rock analysis and maturity modelling.

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.

The Cooper Basin is Australia's premier onshore hydrocarbon producing province and hosts a range of conventional and unconventional gas play types. This study investigates the petroleum generation potential of the basin's major Permian source rocks, to improve regional understanding of the basin's hydrocarbon prospectivity. Source rock distribution, thickness, present-day amount of total organic carbon (TOC), quality (Hydrogen Index) and maturity were mapped across the basin, together with original source quality maps prior to the on-set of generation. Results of the source rock property mapping and basin-specific kinetics were integrated with 1D burial and thermal history models and a 3D basin model to create a regional pseudo-3D petroleum system model for the basin. The modelling outputs quantify the spatial distribution of both the maximum possible hydrocarbon yield, as well as the oil/ gas expelled and retained, for ten Permian source rocks. Monte Carlo simulations were used to quantify the uncertainty associated with hydrocarbon yields and to highlight the sensitivity of results to each input parameter. The principal source rocks are the Permian coal and coaly shales of the Gidgealpa Group, with highest potential yields from the Patchawarra Formation coals and coaly shales. The broad extent of the Cooper Basin's Permian source kitchen and its large total generation potential (P50 scenario >2000 bboe) highlights the basin¿s significance as a world-class hydrocarbon province. The difference between the P90 (~800 bboe) and P10 (>4000 bboe) scenarios demonstrate the range of uncertainties inherent in this modelling.

Interpretation of newly acquired seismic data in the northern Houtman Sub-basin (Perth Basin) suggests the region contains potential source rocks similar to those in the producing Abrolhos Sub-basin. The regionally extensive late Permian–Early Triassic Kockatea Shale has the potential to contain the oil-prone Hovea Member source interval. Large Permian syn-rift half-graben, up to 10 km thick, are likely to contain a range of gas prone source rocks. Further potential source rocks may be found in the Jurassic-Early Cretaceous succession, including the Cattamarra Coal Measures, Cadda shales and mixed sources within the Yarragadee Formation. This study investigates the possible maturity and charge history of these different source rocks. A regional pseudo-3D petroleum systems model is constructed using new seismic interpretations. Heat flow is modelled using crustal structure and possible basement composition determined from potential field modelling, and subsidence analysis is used to investigate lithospheric extension through time. The model is calibrated using temperature and maturity data from 9 wells in the Houtman and Abrolhos sub-basins. Source rock properties are assigned based on an extensive review of TOC, Rock Eval and kinetic data for the offshore northern Perth Basin. Petroleum systems analysis results show that Permian, Triassic and Early Jurassic source rocks may have generated large cumulative volumes of hydrocarbons across the northern Houtman Sub-basin, whilst Middle Jurassic‒Cretaceous sources remain largely immature. However the timing of hydrocarbon generation and expulsion with respect to trap formation and structural reactivation is critical for the successful development and preservation of hydrocarbon accumulations.

Presentation from the Exploring for the Future Roadshow on the Energy prospectivity of the South Nicholson region, regional geochemical data acquisition and shale gas prospectivity analysis.