The approach of the new millennium saw some significant changes in the mining exploration industry including increased use of the acoustic scanner (ATV) and sonic downhole logging tools. MBGS realised that although these tools were often included with the traditional logging suite, their application was not being fully utilised. In 2000 MBGS partnered with Seedsman Geotechnics and formed ASIMS – Acoustic scanner and Sonic log Interpretation MBGS and Seedsman.

For 20 years, ASIMS has been at the forefront of acoustic scanner interpretation and sonic log analysis, carried out by experienced geologists. For the last two decades ASIMS has assisted clients throughout Australia and overseas on predominantly coal projects in NSW (Hunter Valley, Western and Southern coalfields, Gloucester Basin), Queensland (Bowen, Surat and Galilee basins), Western Australia (Canning and Collie basins), Colombia, Mozambique, Indonesia, Canada and Alaska. In later years, metalliferous projects in NSW and South Australia have utilised ASIMS’ capability to provide orientation data on sub-surface discontinuity features that tend to influence block caving characteristics.

The ASIMS team comprises two Senior Geologists, Stacey Pell and Kim Straub, who have over 40 years of experience between them. Both spent their early years in the field learning the geology trade by supervising exploration drill rigs, and in the process have gained the type of expertise and geological understanding that only comes from working at ‘the coal face’. They have presented at several conferences, authored papers and worked closely with Seedsman Geotechnics on a variety of geotechnical projects.

And what exactly does ASIMS find in the acoustic scanner and sonic logs? Accurate defect orientation data within coal-bearing sequences and hard rock domains, definition of geotechnical joint sets (not averages of the data), Principal Horizontal Stress (PHS) directions, calculated UCS data, Rock Strength Index (RSI) and massive units. All of these are critical for open cut and underground mine planning in such areas as validating the structural model, designing the pit wall and roof/ rib supports, optimizing orientation of the longwall face and panels, planning for gas drainage and hazard reduction.

Case study – Applying the data to an open cut issue: An open cut mine in the NSW Hunter Valley recently experienced significant geotechnical issues with pit wall stability, where the interaction of joint sets caused wedge failures along the endwall and sterilisation of around 1Mt of coal. ASIMS used the interpreted acoustic scanner data from approximately 100 holes to create a joint domain model, supporting the successful re-design of the endwall orientation. This allowed parts of the previously sterilised coal to be recovered.

This case study is available on the MBGS website under Publications, and an updated paper will be available soon!

But what about automated picking? Not the preferred method for this team. ASIMS has found that automatic picking software tends to over-represent low angle features, often overlooks critical geotechnical defects that are more steeply dipping (particularly joints and faults), fails to provide precision on depositional bedding dip or direction and can misclassify defects. With ASIMS, every defect is manually picked, and if available core photographs can be cross-checked against geotechnical and lithological logs in the cored sections. Manual picking results in a high confidence data set that accurately reflects the geotechnical properties within each borehole. This type of expertise means that orientation data can even be extracted from poorly drilled and/or non-core boreholes, ensuring the highest possible range and quality of data for their clients.

The old saying “you get what you pay for” rings true here. ASIMS’ clients understand that manual picking and extracting reliable geotechnical and rock strength data is a sound investment when identifying potential hazards.

Keep an eye out in 2021 for ASIMS’ latest paper, comparing the results of manual and automated picking, it will be an interesting and informative read!