The hydrocarbon generative potential and the thermal maturity of source rocks in the offshore northern Perth Basin was reassessed based on existing and new geochemical data to get a better understanding of the basin's prospectivity. The study establishes for the first time that the main source of onshore accumulations, the Late Permian-Early Triassic Hovea Member, is well developed offshore and contains organic-rich sediments of oil-prone character. This finding shatters the long-held view that the Hovea Member was either absent or of poor quality offshore and provides a new perspective on the basin's prospectivity. The source potential of the Hovea Member varies spatially with best source rocks observed in the Beagle Ridge and Central Abrolhos Sub-basin. The Late Permian Irwin River Sequence and several Jurassic Sequences are also identified as prime potential source rocks offshore, mostly for their gas-generative potential. Oil-generative potential was identified in the Middle to Late Jurassic Yarragadee Sequence and possibly in the Middle Jurassic Cadda Sequence.

Geoscience Australia currently uses two commercial petroleum system modelling software packages, PetroMod https://www.software.slb.com/products/petromod and Zetaware http://www.zetaware.com, to undertake burial and thermal history modelling on wells in Australian sedimentary basins. From the integration of geological (age-based sedimentary packages, uplift and erosional events), petrophysical (porosity, permeability, and thermal conductivity) and thermal (downhole temperature, heat flow, vitrinite reflectance, and Tmax) input data, to name the most significant, a best-fit model of the time-temperature history is generated. Since the transformation of sedimentary organic matter (kerogen) into petroleum (oil and gas) is a chemical reaction, it is governed by chemical kinetics i.e. time and temperature (in the geological setting, pressure is of secondary importance). Thus, the use of chemical kinetics associated with a formation-specific, immature potential source rock (where available) from the basin of interest is considered a better practical approach rather than relying on software kinetic defaults, which are generally based on the chemical kinetics determined experimentally on Northern Hemisphere organic matter types. As part of the Offshore Energy Systems program hydrocarbons from the Lower Cretaceous Eumeralla Formation were selected where available from onshore wells; compositional kinetics (1-, 2-, 4- and 14-component (phase) kinetics) were undertaken by GeoS4, Germany. The phase kinetics approach is outlined in Appendix 1. This report provides the compositional kinetics for potential source rocks from the Lower Cretaceous Otway Group, Otway Basin, Australia. The kinetic data were used in the offshore petroleum system modelling reported in Schenk et al. (2021).

Geoscience Australia and its predecessors have analysed the hydrochemistry of water sampled from bores, surface features, rainwater and core samples (pore water). Samples have been collected during drilling or monitoring projects, including Exploring for the Future (EFTF). The hydrochemistry database includes physical-chemical parameters (EC, pH, redox potential, dissolved oxygen), major and minor ions, trace elements, isotopes and nutrients. The resource is accessible via the Geoscience Australia Portal <a href="https://portal.ga.gov.au/">(https://portal.ga.gov.au/)</a>

The Otway Basin is a northwest-southeast trending rift basin which spans from onshore Victoria and South Australia into the deep-water offshore. The prospective supersequences within the basin are largely of Cretaceous age which host three possible petroleum systems (Austral 1, 2 and 3). While there is production from onshore depocentres, and the inboard Shipwreck Trough, the majority of the offshore basin remains underexplored. Recent regional studies have highlighted the need for further work across the underexplored parts of the basin and here we focus on the offshore northwest Otway Basin, integrating reinterpreted historical well data, newly acquired and recently reprocessed seismic data. This new Well Folio consists of composite logs and supporting data which includes interpreted lithologies, petrophysical analyses, the analysis of historic organic geochemistry and organic petrology. In addition, updated well markers are provided based on seismic interpretation and new biostratigraphy in key wells. This integrated study provides the basis for renewed prospectivity assessment in the northwest offshore portion of the Otway Basin.

<div>The Birrindudu Basin is a region of focus for the second phase of the Geoscience Australia’s Exploring for the Future (EFTF) program (2020–2024). The Paleo to Mesoproterozoic Birrindudu Basin is an underexplored frontier basin located in northwestern Northern Territory and northeastern Western Australia. Interpretation of industry seismic data indicates it contains strata of similar age to the prospective McArthur Basin, South Nicholson region and Mount Isa Province, but remains comparatively poorly understood. Furthermore, much of the age of the stratigraphy of the Birrindudu Basin, particularly the younger stratigraphic units, and regional correlations to the greater McArthur Basin remains provisional and speculative.&nbsp;</div><div><br></div><div>This report presents data from Rock-Eval pyrolysis analyses undertaken by Geoscience Australia on selected rock samples to establish their total organic carbon content, hydrocarbon-generating potential and thermal maturity from 178 drill core samples from six drill holes intersecting units of the Birrindudu Basin including: 99VRNTGSDD1, 99VRNTGSDD2, WLMB001B, LBD2, LMDH4, and ANT003. </div><div><br></div>

<div>NDI Carrara 1 is a deep stratigraphic drill hole completed in 2020 as part of the MinEx CRC National Drilling Initiative (NDI) in collaboration with Geoscience Australia and the Northern Territory Geological Survey. It is the first stratigraphic test of the Carrara Sub-basin, a depocentre newly discovered in the South Nicholson region based on interpretation from seismic surveys (L210 in 2017 and L212 in 2019) acquired as part of the Exploring for the Future program. The drill hole intersected approximately 1120 m of Proterozoic sedimentary rocks unconformably overlain by 630 m of Georgina Basin carbonates.&nbsp;</div><div>Geoscience Australia has undertaken a range of investigations on the lithology, stratigraphy and geotechnical properties of NDI Carrara 1 as well as undertaking a range of analyses of about 500 physical samples recovered through the entire core. Analyses included geochronology, isotope studies, mineralogy, inorganic and organic geochemistry, petrophysics, geomechanics, thermal maturity and petroleum systems investigations.</div><div>Rock-Eval pyrolysis raw data undertaken by Geoscience Australia were reported in Butcher et al. (2021) on selected rock samples to establish their total organic carbon content, hydrocarbon-generating potential and thermal maturity. Interpretation of the Rock-Eval pyrolysis data concluded that a large portion of rocks within the Proterozoic section displayed unreliable Tmax values due to poorly defined S2 peaks resulting from high thermal maturity and low hydrogen content. In order to obtain more reliable Tmax values, Rock-Eval pyrolysis of selected isolated kerogens, where organic matter is concentrated and mineral matrix effects are removed, were conducted and the resulting data are presented in this report.&nbsp;</div><div><br></div>

<b>Legacy service retired 29/11/2022 IMPORTANT NOTICE:</b> This web service has been deprecated. The Australian Onshore and Offshore Boreholes OGC service at https://services.ga.gov.au/gis/boreholes/ows should now be used for accessing Geoscience Australia borehole data. This is an Open Geospatial Consortium (OGC) web service providing access to Australian onshore and offshore borehole data. This web service is intended to complement the borehole GeoSciML-Portrayal v4.0 web service, providing access to the data in a simple, non-standardised structure. The borehole data includes Mineral Drillholes, Petroleum Wells and Water Bores along with a variety of others types. The dataset has been restricted to onshore and offshore Australian boreholes, and bores that have the potential to support geological investigations and assessment of a variety of resources.

A regional hydrocarbon prospectivity study was undertaken in the onshore Canning Basin in Western Australia as part of the Exploring for the Future (EFTF) program, an Australian Government initiative dedicated to driving investment in resource exploration. As part of this program, significant work has been carried out to deliver new pre-competitive data including new seismic acquisition, drilling of stratigraphic wells 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, Barnicarndy 1, was drilled in 2019 in partnership between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA) in the Barnicarndy Graben, 67 km west of Telfer, in the South West Canning Basin. Drilling recovered about 2100 m of continuous core from 580 mRT to the total driller’s depth (TD) of 2680.53 mRT (Normore and Rapaic, 2020). An extensive analytical program was carried out to characterise the lithology, age and depositional environment of these sediments. This included detailed organic geochemistry including isotopic and biomarker analyses of core samples. In order to determine the possible presence of organic contaminants in core samples that may jeopardise interpretation of results, manufactured products used during drilling and sample processing were identified as potential sources of hydrocarbon contamination and were investigated for their hydrocarbon content. In addition, in order to test if any hydrocarbon contamination was occurring due to contact with these manufactured products, water samples from the sumps and surface samples of drill muds from specific depths were collected and analysed as well.

The Browse Basin, located offshore on Australia's North West Shelf, contains major natural gas accumulations, some of which present high abundances of helium. The basin also contains large quantities of CO2 with some wells containing up to ~18 mol% CO2. Currently there is no information as to the origins of He and CO2 within the Browse Basin, despite this providing important information to the evolution of the natural gas. By understanding where components of the gas originate, it is possible to make predictions about areas that may be high in CO2, which would be problematic for production; conversely areas rich in He could present a second revenue stream from the same well.

<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.</div><div><br></div><div>The Paleo to Mesoproterozoic Birrindudu Basin is an underexplored frontier basin located in northwestern Northern Territory and northeastern Western Australia. The Birrindudu Basin is a region of focus for the second phase of the EFTF program (2020–2024) as it contains strata of similar age to the prospective McArthur Basin, South Nicholson region and Mount Isa Province, but remains comparatively poorly understood.</div><div><br></div><div>Geoscience Australia have undertaken (via the service provider, FIT, Schlumberger) Fluid Inclusion Petrography and Microthermometry analysis of samples for the drillhole 99VRNTGSDD1, Birrindudu Basin, located in the northwest Northern Territory (Company reference number MT#F1230005c).</div><div><br></div><div>This eCat Record accompanies the report containing the results of fluid inclusion stratigraphy on this drillhole (eCat record 148973).</div>