This study compares cover thickness estimates from geophysical techniques acquired prior to drilling to preliminary results from the Coompana Drilling Program in the far west of South Australia. Prior to drilling, geophysical techniques consisting of magnetotellurics (MT) and reflection and refraction seismic were deployed to estimate the thickness of Cenozoic cover sediments at the proposed drill-sites. The estimates of cover thickness assisted with planning the Coompana Drilling Program and helped to de-risk the stratigraphic drilling by providing estimates of cover thickness.

The Neoproterozoic to Paleozoic Thomson Orogen is a major component of the Tasmanides of eastern Australia that extends through large portions of central and southwest Queensland and northwest New South Wales. Much of the Thomson Orogen is buried under younger sedimentary basins (some up to several kilometres thick) and regolith cover, making it one of the most poorly understood elements of Australia’s geology. As a result, the mineral potential of the region is also poorly defined. The Southern Thomson Project (the Project) is a collaborative investigation between the Commonwealth of Australia (Geoscience Australia – GA) and its partners the State of New South Wales (Department of Trade and Investment, Geological Survey of New South Wales – GSNSW) and the State of Queensland (Department of Natural Resources and Mines, Geological Survey of Queensland – GSQ). The Project aims to better understand the geological character and mineral potential of the southern Thomson Orogen region, focusing on the border between New South Wales and Queensland, by acquiring and interpreting multi-disciplinary geophysical, geochemical and geological data. The primary intended impact of this work is to provide the mineral exploration industry with pre-competitive data and knowledge that reduces risk and encourages mineral exploration in the region.

<div>Elastic seismic waves propagate in the solid Earth and contain valuable information for inferring subsurface physical properties. Traditionally, the data acquisition requires active artificial sources for generating seismic waves, which can be air-gun arrays for offshore seismic surveys, and explosive or vibroseis sources for onshore seismic surveys. Active-source seismic data have a wide frequency spectrum often from 4 Hz to 50 Hz and contain reflected and refracted P and S waves and surface waves, which have been widely used for obtaining high-resolution images of subsurface structures across industry and academia in the past decades. In this report, we study the feasibility of combining seismic data from borehole drilling (drilling noise) and the state-of-the-art seismic imaging technique, reverse time migration, for a direct migration (imaging) of drilling-generated seismic noise data without intermediate steps (such as seismic interferometry for virtual common-source seismic data), in the aim of obtaining subsurface structural images. The developed imaging method enables informed decision-making during the drilling process by revealing the three-dimensional structure beneath the drill rig. With precise knowledge of the depth to bedrock and the surrounding geological formations, better planning can be achieved, significantly reducing both costs and time.</div>