The Ordovician to Cretaceous Canning Basin of Western Australia is an underexplored prospective onshore petroleum basin with proven petroleum systems currently producing on a small-scale. The Canning Basin has recently become a site of interest for unconventional hydrocarbon exploration, with several formations within deeper basin depocentres being investigated for resources and estimates that suggest it may have the largest shale gas potential in Australia. Modern petroleum resource evaluation generally depends on an understanding of both local and regional stresses, which are a primary control over the formation and propagation of induced fractures. Presently, there are significant gaps in our understanding of these factors within the Canning Basin. This study characterises the regional stress regime of the onshore Canning Basin and presents detailed models of present-day stress within the subsurface. These allow for the identification of significant stress heterogeneities and natural barriers to fracture propagation. Wireline data interpretation reveals a variable present-day state of stress in the Canning Basin. An approximately NE-SW regional present-day maximum horizontal stress orientation is interpreted from observed wellbore failure in image logs, in broad agreement with both the Australian Stress Map and previously published earthquake focal mechanism data. One-dimensional mechanical earth models constructed for intervals from 15 Canning Basin petroleum wells highlight the relationship between lithology and stress. This study describes significant changes in stress within and between lithological units due to the existence of discrete mechanical units, forming numerous inter- and intra- formational stress boundaries likely to act as natural barriers to fracture propagation, particularly within units currently targeted for their unconventional resource potential. Broadly, a strike-slip faulting stress regime is interpreted through the basin, however, when analysed in detail there are three distinct stress zones identified.: 1) a transitional reverse- to strike-slip faulting stress regime in the top ~1 km of the basin, 2) a strike-slip faulting stress regime from ~1 km to ~3.0 km depth, and 3) a transitional strike-slip to normal faulting regime at depths greater than ~3.0 km. This study is a component of the Australian Government’s Exploring for the Future (EFTF) initiative, which is focused on gathering new data and information about the resource potential concealed beneath the surface across northern Australia. Appeared online in the Australian Journal of Earth Sciences 17 Feb 2021

A key focus of the Exploring for the Future program was the Kidson Sub-basin, a large, underexplored and poorly understood depocentre in the southern part of the Canning Basin of Western Australia. The Canning Basin hosts proven petroleum systems and has recently become an area of interest for unconventional hydrocarbon exploration. Several formations within deeper basin depocentres are under investigation. Unconventional petroleum resource evaluation is generally dependent on an understanding of both local and regional stresses, as these exert a control over subsurface fluid flow pathways, as well as the geomechanical properties of reservoir units. Gaps exist in our understanding of these factors within the Canning Basin, and particularly the Kidson Sub-basin where wellbore coverage is sparse. This study identifies a generally NE–SW-oriented regional maximum horizontal stress azimuth from interpretation of borehole failure in five petroleum wells, and a broadly strike–slip faulting stress regime from wireline data and wellbore testing. Variations in stress regime at different crustal levels within the basin are highlighted by one-dimensional mechanical earth models that show changes in the stress regime with depth as well as by lithology, with a general shift towards a normal faulting stress regime at depths greater than ~2.5 km. <b>Citation:</b> Bailey, A.H.E. and Henson, P., 2020. Present-day stresses of the Canning Basin, WA. 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.

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.

High-precision radiometric dating using Chemical Abrasion-Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) has allowed the recalibration of the numerical ages of Permian and Triassic spore-pollen palynozones in Australia. These changes have been significant, with some zonal boundaries in the Permian shifting by as much as six million years, and some in the Triassic by more than twice that. Most of the samples analysed came from eastern Australian coal basins (Sydney, Gunnedah, Bowen, Galilee) where abundant volcanic ash beds occur within the coal-bearing successions. The recalibrations of these widely used palynozones have implications for the dating of geological events outside the basins from where samples were obtained. Our revised dates for the Permian palynozones can now be applied to all Permian basins across Australia, including the Perth, Carnarvon, Canning and Bonaparte basins (along the western and northern continental margins), the Cooper and Galilee basins (in central Australia), and the Bowen, Gunnedah and Sydney basins (in eastern Australia). Revised regional stratigraphic frameworks are presented here for some of these basins. The impact of an improved calibration of biostratigraphic zones to the numerical timescale is broad and far-reaching. For example, the more accurate stratigraphic ages are the more closely burial history modelling will reflect the basin history, thereby providing control on the timing of kerogen maturation, and hydrocarbon expulsion and migration. These improvements can in turn be expected to translate in to improved exploration outcomes. We have initially focused on the Permian and provide preliminary results for the Triassic, but intend to expand recalibrations to include Jurassic, Cretaceous and Paleozoic successions beyond the Permian. Preliminary data indicates that significant changes to these calibrations are also likely.

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.

The Kidson Sub-basin covers ~91 000 km2, and is a largely under-explored and sparsely imaged region of the Canning Basin in northern Western Australia. The 872 km Kidson Sub-basin seismic survey was acquired to enhance understanding of the subsurface and thereby assist in the assessment of the region for hydrocarbon and mineral potential. Specifically, the survey aimed to improve basin-wide stratigraphic correlation, determine the extent of basin depocentres, image major structures and place constraints on the sub-basin’s geological event history. The new seismic profile reveals that the Kidson Sub-basin is ~500 km long and ~6.5 km deep. It contains a lower conformable package of Ordovician to Devonian clastic sediments, carbonates and evaporites unconformably overlain by the clastic-dominated Permian Grant Group and Poole Sandstone. Normal faults imaged at the base of the sequence with growth strata in the hanging wall constrain rifting to between Cambrian and Silurian in age. Folding along the southeastern edge of the basin is inferred to be a consequence of the Carboniferous Meda Transpression linked to the Alice Springs Orogeny in central Australia. The known source rocks of the Goldwyer and Bongabinni formations have been interpreted to extend across the Kidson Sub-basin, which is encouraging for energy prospectivity in the region. <b>Citation:</b> Southby, C., Carr, L.K., Henson, P., Haines, P.W., Zhan, A., Anderson, J.R., MacFarlane, S., Fomin, T. and Costelloe, R., 2020. Exploring for the Future: Kidson Sub-basin seismic interpretation. 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.

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

This report presents the results of chemostratigraphic analyses for samples of the Waukarlycarly 1 deep stratigraphic well drilled in in the Waukarlycarly Embayment of the Canning Basin. The drilling of the well was funded by Geoscience Australia’s Exploring for the Future initiative to improve the understanding of the sub-surface geology of this underexplored region of the southern Canning Basin. The well was drilled in partnership with Geological Survey of Western Australia (GSWA) as project operator. Waukarlycarly 1 reached a total depth (TD) of 2680.53 m at the end of November 2019 and was continuously cored from 580 mRT to TD. The work presented in this report constitutes part of the post-well data acquisition. An elemental and isotope chemostratigraphic study was carried out on 100 samples of the well to enable stratigraphic correlations to be made across the Canning Basin within the Ordovician section known to host source rocks. Nine chemostratigraphically distinct sedimentary packages are identified in the Waukarlycarly 1 well and five major chemical boundaries that may relate to unconformities, hiatal surfaces or sediment provenance changes are identified. The Ordovician sections in Waukarlycarly 1 have different chemical signals in comparison to those in other regional wells, suggestive of a different provenance for the origin of the sediments in the Waukarlycarly Embayment compared to the Kidson Sub-basin (Nicolay 1) and Broome Platform (Olympic 1).

Exploring for the Future Roadshow- Regional petroleum systems visualised in the EFTF Data Discovery Portal. A summary of petroleum systems of the Canning Basin and regional Meso- and Paleoproterozoic basins of northern Australia, and an introduction to the EFTF Data Discovery Portal

<div>The Canning Basin is a prospective hydrocarbon frontier basin and is unusual for having limited offshore seismic and well data in comparison with its onshore extent. In this study, seismic mapping was conducted to better resolve the continuity of 13 key stratigraphic units from onshore to offshore to delineate prospective offshore hydrocarbon-bearing units, and better understand the distribution of mafic igneous units that can compartmentalise migration pathways and influence heat flow. The offshore Canning Basin strata are poorly constrained in six wells with limited seismic coverage; hence data availability was bolstered by integrating data from the onshore portion of the basin and adjacent basins into a single 3D seismic stratigraphic model. This model integrates over 10 000 km of historical 2D seismic data and 23 exploration wells to allow mapping of key stratal surfaces. Mapped seismic horizons were used to construct isochores and regional cross-sections. Seven of the 13 units were mapped offshore for the first time, revealing that the onshore and offshore stratigraphy are similar, albeit with some minor differences, and mafic igneous units are more interconnected than previously documented whereby they may constitute a mafic magmatic province. These basin-scale maps provide a framework for future research and resource exploration in the Canning Basin. To better understand the basin’s geological evolution, tectonic history and petroleum prospectivity, additional well data are needed in the offshore Canning Basin where Ordovician strata have yet to be sampled.</div><div><br></div><div>C. T. G. Yule, J. Daniell, D. S. Edwards, N. Rollet & E. M. Roberts&nbsp;(2023).&nbsp;Reconciling the onshore/offshore stratigraphy of the Canning Basin and implications for petroleum prospectivity,&nbsp;Australian Journal of Earth Sciences,&nbsp;DOI:&nbsp;10.1080/08120099.2023.2194945</div> Appeared in Australian Journal of Earth Sciences Pages 691-715, Volume 70, 2023 - Issue 5.