Adelaide was the second stop for the DISC in Australia (and was a little cooler and wetter than Perth!). To date, this audience was the group with the strongest background in EM geophysics. Many of the participants work with Geoscience Australia or CSIRO, several are professors, postdocs or graduate students at the University of Adelaide, and several are with smaller mining or consulting companies. A number of participants had direct connections with two of the case histories presented during the course: the Mt. Isa and Bookpurnong case histories, either having been involved in data collection or having worked with data from those sites.
Day 1: DISC Course
Day 1 took place downtown at the Hotel Richmond and started with introductions from each of the 30 participants. Applications of particular interest included:
- mineral exploration, in fact, several participants are now helping review the Mt. Isa case history on EM GeoSci
- water, monitoring the salinization of the Murray river
- airborne EM and setting standards for the data and meta-data delivered by providers (we will come back to this when discussing DISC Lab),
- magnetotellurics (several of the participants are involved in AusLAMP, an ambitious project to collect MT data over the entirety of Australia, tectonic studies)
From the participants
“Fantastic — Great explanations with useful examples. Comprehensive and very helpful” — Graham Heinson, Professor
“Exceptional, accessible and understandable. Lecturer’s enthusiasm is contagious” — Jim Allender, Geophysicist
“Great overview of EM. Very intense course. Good balance: theory, insight, case studies” — Luk Peeters, Research Scientist- Hydrogeologist
“Well presented and good overview of EM theory and methods for the non-geophysicist. The ‘Apps’ are excellent for visualizing and understanding of all the different parameters and effects of EM currents” — Andy Burtt, Senior Geologist
“Good value. Packed a lot in. Would recommend to other geologists in exploration. Found it a great way to bridge my knowledge with contractors and geophysicists.” — Barry Vanderstelt, Exploration Geologist
“Very good. I liked the focus on establishing a collaboration platform. The course has the potential of raising the bar and establishing common terminology.” — Yusen Ley-Cooper, Geophysicist
All presentation material from Adelaide is available at: http://disc2017.geosci.xyz/adelaide
Day 2: DISC Lab
DISC Lab was held at the University of Adelaide. We started with some additional material that was not covered in Day 1, including further discussion Induced polarization and the Tli Kwi Cho case history.
Following the additional presentation material from the DISC team, 9 participants were willing to share the projects they are working on.
Presentations from participants
James Ohanga (slides) works with Groundwater Imaging. He introduced applications for which they are using EM including monitoring for canal and reservoir seepage, characterizing soil moisture, and mapping groundwater and alluvium. Some of the equipment that Groundwater Imaging relies on has been developed in-house, including their Hydrographic Electrical Resistivity & Bathymetry Imager (HERBI) which tows electrodes along the water for conducting a DC resistivity survey and the AgTEM, a time domain EM system that can be towed by a vehicle on land.
Graham Heinson (AusLamp slides, MT for monitoring slides) is a geophysics professor at the University of Adelaide. He gave two presentations — the first related to AusLamp, the second using MT for monitoring subsurface injections. AusLamp (the Australian Lithospheric Architecture Magnetotelluric Project) is a project aimed at collecting long period MT data over all of Australia. The data collected are considered “competitive data” in that they provide information about the geologic history and evolution of the Australian continent. There is significant interest from the mineral exploration side of things as they are interested in locating deep sources of fluids (beneath the electrically conductive regolith that covers most of Australia!). In his second presentation, Graham discussed the potential use of natural source EM methods for monitoring injection / extraction of subsurface fluids associated with the development on unconventional resources (eg. Hydraulic fracturing for oil and gas or engineered geothermal, extracting methane from coal seams, …). These problems have lots of constraints: we know volumes of fluids injected or extracted and can obtain information about physical properties of fluids, but we are also looking for subtle changes through time in the electrical resistivity associated with the injection / extraction.
Chris Li (slides) is a PhD student with Graham Heinson and is starting his PhD work on using geophysics to improve groundwater models that are used for making decisions on how to manage groundwater resources. He is interested in using NMR and EM to obtain information about groundwater salinity and in investigating how geophysical data can be included in groundwater models, as model inputs, calibration constraints or potentially moving towards joint inversions.
Luk Peeters (slides) is a hydrologist at CSIRO with a background in groundwater and uncertainty analysis. He is part of the supervising team for the Deep Earth Imaging Future Science Program, discussed in the Perth article. He is introduced challenges in water resource assessment: Where can we find a source of water, with low enough salinity (eg. for irrigated agriculture), and importantly, a source of water that can be extracted without compromising baseflow to springs, rivers or existing water-wells? Having reliable groundwater models is essential for making these management decisions, and Luk is interested in improving groundwater modelling by incorporating geophysics as well as tracers.
David McInnes (slides) is with Geoscience Australia (GA) and is involved in managing and quality controlling geophysical data with GA. One of the common problems encountered with managing (and resurrecting) historical data is that often the meta-data is lost, or was never captured in the first place, so all you are left with is a data file with numbers and no information on how it was filtered, what the waveform was, … For interpretations a decade or two ago, compute resources were much more limited and a plot of the data may have been all that was done, so the meta-data were not perceived to be significant. Now, however, we can perform 3D simulations and inversion, but to do so requires that we know the details of the survey. This requires a shift in how data are delivered and stored, and Geoscience Australia is working on developing and promoting standards for data delivery of airborne EM data sets in Australia. David also introduced the Australian National Virtual Geophysical Laboratory initiative — an effort to make data and compute resources widely accessible, particularly for industry, for working with geophysical data in Australia.
Laz Katona (slides) is a geoscientist with the Geologic survey of South Australia. He presented work on a collaborative project with GeoIntrepid Consulting Services modelling and inverting airborne electromagnetic data with recently-developed 1D and 2.5D EM inversion codes. They are re-inverting historic data with updated inversion algorithms; the aim is to pull new information out of the old data. One application of particular interest with these data is uranium exploration in Southern Australia. These data and report are publicly available and those who are interested are encouraged to compare their results!
Yusen ley-Cooper (slides) works with Geoscience Australia and he presented 2 topics. First he introduced AusEM, an ambitious 4 year project that will include the collection of airborne EM survey over 10⁶ km² of Australia. It is affiliated with the AusLamp project under the “Exploring for the future” initiative by Geoscience Australia (and the first flights started the day of DISC lab!). Yusen also provided an overview of how legacy Airborne EM data sets are being reprocessed and re-purposed. After 5 years, airborne EM data sets flown for mineral exploration are turned over to Geoscience Australia. In order to perform quantitative modelling and inversion, the specifications of the airborne EM system must be adequately characterized. Inaccuracies in parameters such as the area under the curve or ramp-off character in the transmitter waveform can have significant impacts in the electromagnetic responses. He presented a slide that describes a number of AEM systems that Geoscience Australia has data from and how they have changed through time-this prompted some discussion in the group! Interestingly, many of the legacy data sets that were originally collected for mineral exploration are now being re-examined in an environmental context for the purpose of characterizing groundwater.
Matthew Hutchens (slides) is exploring ideas around using DC resistivity for Opal exploration in Australia. Opal is mined from the Bulldog Shale, an electrically conductive unit. The Bulldog Shale is variable, some regions are considered “good sandstone” where opal is hosted as a replacement of bio-features (eg. shells, burrows), and other regions are considered “bad sandstone” or “blue ground” which are weathered. There are questions around which physical properties might be diagnostic for finding more prospective regions.
Kleanthis Simyrdanis (slides) is working on locating and mapping shipwrecks at the Murray River. There are more than 77 shipwrecks in the Murray river, but it is difficult to see them as the Murray river is quite murky. There is a known shipwreck, called ‘Crowie’ which has been previously mapped using Side Scan Sonar and Multi Beam. This will serve as a base-case for testing the use of towed DC and EM techniques (either floating on the surface or submerged) for detecting and mapping shipwrecks.
Following the presentations from participants, we introduced SimPEG and walked through a couple simulation and inversion examples, including the example of a frequency domain EM sounding over a conductive sphere as shown in the EM Fundamentals presentation on Day 1. We also introduced the SimPEG forum as a means to connect with the SimPEG community. With that, we wrapped up DISC Adelaide.
A few adventures
Wanting to experience some “authentic” Australian cuisine, we asked around and were told by Mike McWilliams (from Perth) that a pie floater is a classic Adelaide cuisine. What is a pie floater you ask… Well. It is a savoury pie in pea soup. Sounds strange, looks strange, and in fact the owner of the pie stand who made it for us had never had one herself — but it was good! One shared between the two of us was enough for the entire day.
Following the DISC presentation, David McInnes and John Paine invited us to join them for a Thai food dinner. Among the dishes, we tried some Barramundi, a fish common to Australia. This was certainly the best Thai food I have ever had.
On our final full day in Adelaide, we took a bus up into the Adelaide Hills. As we climbed, we went through some weather swings — intense wind, some raid and a couple breaks with sunshine. Thinking that Australia is all about beaches and surfing, both Doug and I were a little under-prepared for the fact that August is in fact winter there. We went to the town of Hahndorf, which was a German settlement and still maintains a lot of German influence. From the town, we walked to the Hahndorf Hills winery (with a bit of rain, but we saw 4 rainbows on the way there!) and had a sampling of wine paired with chocolate. Not a bad afternoon.
Thanks to the ASEG for support in organizing the Adelaide DISC, in particular Josh Sage and Emma Brand.