b'AEGC 2023Short abstractsdata with sufficient resolution for gravity to be used as astorage, survey design and acquisition systems. Regional-scale complementary dataset on a prospect scale for both 2D and 3Dcompilations of these data are created by merging grids of geological interp and targeting. Airborne electromagnetics hasthese individual surveys together with the aim of creating a been used to map carbonaceous units within the stratigraphicseamless image. These compilations do not convey the variation sequence, map the depth of cover, and alteration. Passive seismicin quality of the underlying datasets.(HVSR) methods have also been deployed on a large scale to map the depth of cover. A depth of cover map generated from drilling,In 2022 NTGS collaborated with Intrepid Geophysics to audit HVSR, and AEM allows for the effect of deep palaeochannelsthe compilation of regional-scale airborne magnetic and to be accounted for while interpreting affected datasets (bothradiometric data in the Northern Territory. The project assessed geophysical and geochemical). Acoustic impedance contrasts63 survey projects which each contained multiple individual within the conformable stratigraphic sequence at DBS aresurvey parts of varying age and quality. The outcomes of this sufficient to appear as significant seismic reflectors. A recent 3Daudit are being used to quantify the quality of existing data and seismic survey imaged the anticlinorium to depth and down- inform future acquisition projects.plunge, and also mapped parasitic folds along the limbs of the DBS anticlinorium that represent exploration targets. Direct hydrocarbon indications from fluid contacts - stop calling them flatspots!New data, new insights into the Tasmanian cover. Jarrod Dunne, James ParsonsMark Duffett QIntegral Pty LtdMineral Resources Tasmania So called flatspots rarely have the appearance of flatness, Exploration beyond the exposed richly endowed Paleozoic andeven at proven gas and oil fields and on seismic data that Proterozoic terranes of Tasmania has been hampered by thehas been converted to depth using best-practice methods. Permo-Triassic sediments, Jurassic dolerite and Cenozoic basaltThe appearance of fluid contacts on seismic reflection data is that together blanket much of the centre and south-east of theinfluenced by several controls, most notably, fluid type; burial State. The dolerite and basalt are particularly problematic fordepth; saturation; and the size of the flatspot anomaly relative geophysical exploration, being generally magnetic, dense andto the imaging velocity resolution. Whilst these controls are high velocity; also the basalt is often conductive. As a result,important, most cases of non-flatness are caused by lateral both precompetitive and commercial exploration effort hasvelocity variation in the overburden. Often the structural form been largely confined to the uncovered areas. of the trap itself is the cause.Only in recent years has this situation changed. ApproximatelyNon-flat seismic hydrocarbon contacts are observed at shallow 90 000 line km of magnetic and radiometric data have beengas hazards in Sakhalin, Russia; at oil fields in the Santos Basin, flown over central and south-eastern Tasmania across twoBrazil; and gas on oil accumulations in the Browse Basin, Australia. major surveys in 2021 and 2022. This has increased TasmaniasSo it appears that non-flat flatspots are ubiquitous, suggesting an coverage of contemporary high quality, semi-regionalurgent name change is required for this form ofDHI.resolution (200 metre line spacing) magnetics and radiometricsThe interpretation of DHIs is aided by a new 2D synthetic by almost a third. modelling method that characterises the time-depth behaviour The new data reveal a great deal of internal structure andof a field or prospect simultaneously with its amplitude compositional variation within Tasmanias cover units,response. The software interactively models seismic cross-particularly the dolerite. Many of these features have notsections using rock physics or seismic velocities to compute AvO previously been recognised. Among them are extensive faultsynthetics at significant layer boundaries. Hydrocarbon porefill networks and changes in apparent magnetisation that may beeffects can be modelled using Gassmann fluid substitution to related to grain size and other primary petrological controls onmodify the elastic properties within the proposed trap.magnetite characteristics. DHIs are thus characterised at (1) the top of the trap; (2) the The new airborne data are complemented by significantbase of the trap (if base sealed); and (3) at the contacts between recent passive seismic and magnetotelluric datasets acquireddifferent fluid types, such as a gas/water contact; oil/water within the same region over the last decade. These havecontact; or gas/oil contact. We propose a more representative successfully illuminated major aspects of the geology beneathterminology, referring to DHIs as either top reservoir indicators; the cover units. base reservoir indicators or contact indicators, thus removing the rarely met implication that flatspots ought to appear flat Evolution of regional-scale airborne magnetic andon a depth converted seismic section.radiometric data in the NT.Adding rocks to data: Integrating drill core imagery and Tania Dhu 1, Mike Morse2 down-hole data with machine learning.1 Northern Territory Geological SurveyRian Dutch 1,2,Tom Carmichael1, Mahsa Paknezhad1 and 2 Intrepid Geophysics Nathanael Pittaway1Regional-scale airborne magnetic and radiometric data in1 Datarock Pty Ltd the Northern Territory, Australia, has been acquired by the2 University of AdelaideNorthern Territory Government, Commonwealth Government and exploration industry since the 1970s. The quality of theseThe ability to incorporate geological texture into logging is individual surveys vary with advances in data processing andincredibly important to distinguish subtle changes in rock 93 PREVIEW FEBRUARY 2023'