SA

Discovery Day is the premier event for the GSSA and collaborating organisations to deliver data and its geoscientific value to our stakeholders, in particular the minerals industry. This year the wide range of activities of the GSSA will be covered, in particular, the results of recent geological mapping in the central Gawler Craton region, geochemical investigations into the mantle beneath the Gawler Craton and a summary of commodity trends viewed from a South Australian perspective. In addition, we will be having a panel session that looks at the emerging technologies for non-destructive analysis of geological material relevant for mineral exploration.

Discovery Day will also feature an exhibition space with posters and interactive displays of South Australian geology and recent geoscience, including a review of the geology and tectonics of the Kanmantoo Group in the east of South Australia, new geophysical datasets from GCAS. The South Australian Museum exhibit is sure to be a favourite with some spectacular minerals from South Australia on show.

More information and to register

Our next technical event is a lunch on Monday 19th November, by Dr Kristina Tietze, visiting from GFZ, Potsdam, Germany. Kristina’s talk is titled, ‘Imaging fluid imprints along active and fossil margins with 3D magnetotelluric inversion – examples from the San Andreas fault and the Gawler craton.’ Abstract and bio below. This event is co-hosted by the Geological Survey of South Australia, Department for Energy and Mining. Lunch will be provided.

Date & Time: Monday 19th November, 12-1 pm

Location: Rm 4.06A/B, Level 4, 11 Waymouth St (ANZ building), Adelaide.

RSVP: To Philip Heath at Philip.Heath@sa.gov.au by midday, Friday 16th November for catering purposes (and please let Phil know if you have any dietary requirements).

Abstract

Presence of fluids alters stress distribution and lowers mechanical strength of rocks. Moreover, fluids transport minerals e.g. from the mantle into the crust and play an important role in the formation of mineral deposits. Thus, imaging the distribution of fluids is crucial to unravel current and past tectonic regimes as well as to understand the prevalence of mineral resources.

Mapping the electrical resistivity structure is particularly useful in this respect as fluid phases and their remnants usually reduce electrical resistivity of rock formations. Magnetotelluric (MT) measurements are capable of recovering the electrical resistivity structure from surface to mantle depths and may be one of the best means to image fluid networks over wide regions.

At the San Andreas fault (SAF) near Parkfield, 2D and 3D MT surveying with more than 250 sites revealed “along-strike” changes on fluid systems at lower crustal to upper mantle depths where the fault changes its mechanical behaviour from creeping to being locked and where the source region of non-volcanic tremors has been located. Narrow, subvertical low-resistive features were interpreted as a migration pathways for fluids from the mantle into the SAF system which lead to fault weakening and associated creep. Where the fault is locked, a crustal fluid channel is absent. Fluids are suggested to be trapped beneath an impermeable layer at mantle depths and co-located NVT events may be caused by episodic fluid release.

In this context, a new MT inversion approach using the MT phase tensor was implemented which improves 3D resistivity models where data is distorted by near-surface inhomogeneities below the resolution scale of the MT experiment. For the SAF data set, application of the new scheme resulted in more reliable images of the 12 km deep sedimentary basin of the Central Valley. Currently, a comparative study of the new and conventional inversion schemes is run for a set of ~280 AusLAMP sites across South Australia where MT is used to uncover former tectonic processes along fossil margins and understand their relation to mineral deposits.

Biography

Kristina joined the German Research Centre for Geosciences (GFZ Potsdam, Germany) in 2007 after completing her Diploma studies in Geophysics at the Johann Wolfgang Goethe University, Frankfurt. As member of the Geo-Electromagnetics working group she focused on application and development of 3D modelling and inversion approaches for magnetotelluric (MT) data. In 2012, she received her PhD from Freie Universität Berlin and GFZ Potsdam for studies of the electrical conductivity structure along the San Andreas fault system with 3D MT inversion. From 2012-2017 she has been heading a project on developing controlled-source electromagnetic methods for monitoring of fluid flow in reservoirs at GFZ Potsdam.

Currently, she is a visiting researcher at the Geological Survey of South Australia and the University of Adelaide working on 3D inversion and modelling of MT data from the AusLAMP project.

SA/NT 2019 Joint PESA-ASEG-SPE-YPP Mentoring Program

Thanks to all who attended the September Spring Fling Event which included an introduction to the 2019 Joint Mentoring Program. This program is being offered on a collaborative basis by PESA SA/NT, ASEG SA/NT and SPE SA Section to provide an opportunity for Early Career Young Professionals (YPs) to obtain local support in their career development from experienced professional members.

The Mentoring Program is designed to facilitate face-to face mentoring sessions through which industry insights, knowledge and experience are shared to foster the professional and personal development of mentees.

The 2019 program, consisting of six mentoring sessions, will be launched in February/March 2019 and will conclude in November 2019. Detailed information regarding the program and eligibility can be found in the program flyer.

If you are interested in participating in the 2019 Program as a mentor or mentee, please complete and submit the registration form by COB October 31st, 2018. Applicants must be a current member of either PESA SA/NT, ASEG SA/NT OR SPE SA. (See attached detailed program flyer and registration form).

Potential mentors, please do take the time to consider this request, I envision it will be a highly rewarding experience for both mentors and mentees, and the donation of your time would be very greatly appreciated.

Please do not hesitate to contact me with any questions at sa-ntpresident@aseg.org.au

Kind Regards

Kate Robertson

ASEG SA/NT Branch President

Alison Kirkby: Integration of seismic, magnetotelluric and magnetic data to reveal crustal structure in the Arunta region, Central Australia

This presentation will show results from recent 3D inversions of magnetotelluric data along the 09GA-GA1 deep magnetotelluric and seismic reflection transect. The data were acquired from 39 broadband and 18 long period stations. The broadband data have been reprocessed, yielding an extended bandwidth of 0.004 to 1300 s. A 3D isotropic resistivity model provides a good fit to the data; however the presence of off-profile features with a similar spacing to the stations may suggest the presence of anisotropy in the Irindina Province. The resistivity model indicates at lying structure in the Davenport Province and overlying Georgina Basin, which contrasts with a tendency toward sub-vertical structure in the Aileron Province in the southern half of the line. Conductivity anomalies in the Aileron Province coincide with peaks in magnetic susceptibility as defined by inversions of Total Magnetic Intensity data, and are therefore interpreted in terms of a magnetic alteration mineral such as magnetite or an iron sulphide.

Biography

Alison joined Geoscience Australia in 2008 after completing her MSc in Geology at the University of Auckland. She worked in the Geothermal Section at GA until 2013. In 2013, she commenced a PhD at the University of Adelaide with Graham Heinson, looking at the resistivity characteristics of fractured rocks. After completing her PhD in 2016, she joined the MT and Seismic section at GA. Her current work involves developing the MTPy software package for MT data analysis, and the modelling and interpretation of new MT datasets.

The SA/NT Branch is holding a Spring Fling

A night of Drinks, Nibbles and Conversation jointly presented with PESA, The Young Petroleum Professionals, the SPE and the ASEG.

The cost is $10 per head.

RSVP to Lewis.Maxwell@santos.com by 21 st September.

RiAus present Scinema

Join us for the largest science film festival in the southern hemisphere, the SCINEMA International Science Film Festival presented by Australia's Science Channel, RiAus.

We will be screening a compilation of short films on Numbers and Data (program below), recommended for those curious to see how numbers and data shape our culture and drive our decisions.

Everyone is welcome to this event, hosted by the SA/NT branch of the Australian Society of Exploration Geophysicists (ASEG) at a cost of $10 pp includes film, beer, wine (for those 18 years+), softdrink, and pizza. Please arrive at 6 pm for pizza with the film starting at 6:30 pm.

Cost: $10 per person

Book through Eventbrite or by email to SA/NT Branch president.

Seismic Full Waveform Inversion for Fundamental Scientific and Industrial Problems.

Seismic waveform inversion is a powerful method used to quantify the elastic property of the subsurface. Although the development of seismic waveform inversion started in the early 1980s and was applied to solve scientific problems, it became popular in industry only about 15 years ago. One of the key elements in the success of seismic waveform inversion has been the increase of the acquisition of long offset seismic data from 3 km in the early 1990s to more than 15 km today. Not only did long offset data provide refraction arrivals, but it also allowed recording of wide-angle reflections, including critical angles, providing unique information about the subsurface geology.

In this talk, I will elaborate on the early development of the seismic full waveform inversion (FWI) and its application to solve fundamental scientific problems. The first big success of FWI was its application to gas hydrate reflections, also known as bottom simulating reflection (BSR), which showed that the
BSRs are mainly due the presence of a small amount of free methane gas, not a large amount of hydrates stored above the BSR, and hence the total amount of methane stored in marine sediments should be much less than previously estimated. A second major success of FWI was its application to quantify the characteristics of the axial melt lens observed beneath ocean spreading centers. The seismic full waveform inversion results show that one can distinguish between pure melt and partially molten mush within a 50 m thick melt lens, allowing to link the melt delivery from the mantle with the hydrothermal circulation on the seafloor. The application of full waveform inversion to spreading center problems has become an important area of research.

Unlike in sedimentary environment, the seafloor in general scientific environment could be very rough and water depth could be deep, making it very difficult to use the conventional method of background velocity estimation. To address this issue, the surface seismic data could be downward continued to the seafloor, as if both streamer and sources were placed on the seafloor, similar to land geometry. This method allows to bring the refraction starting from zero offset to far offset, which is extremely useful for full waveform inversion of first arrivals. The downward continuation also allows to reduce the seafloor diffraction, increase the moveout of reflection arrivals, and enhance wide-angle reflections, all important for seismic full waveform inversion. The application of a combination of downward continuation and FWI has allowed to quantify gas anomalies in sedimentary basins and fluids at subduction fronts. The waveform inversion also has been used to monitor CO 2 sequestration.

I will explain the intricacy of FWI, based on the physics of waves, specifically the role of amplitudes and converted waves in addressing fundamental scientific problems. The presentation should interest professionals working in the oil and gas sectors, or crustal studies and global seismology.

More details and biography.

'Next week we have a talk by visiting Senior Research Geoscientist Dr Clive Foss from CSIRO Mineral Resources, speaking about 'Paragon Bore – a special place in the South Australian magnetic field.'

This event will be held on Level 7 of 101 Grenfell St, Adelaide in Training Room 1 at 12 pm till 1 pm on Friday 6th July. Bring along a gold coin donation, with a light lunch provided.

Please send through an email to sa-ntpresident@aseg.org.au if you are thinking about coming along, to give us a rough idea of numbers for catering purposes. Don't forget to include any dietary requirements

Finding and exploiting correlations between 3D seismic, log, and engineering data using machine learning or

The future requirements of integrated E&P: Shallow learning – but deep thinking!

Kurt Marfurt's SEG DISC will tour Australia between 11 and 25 July. After each day-long course, Kurt will speak at selected branch technical nights. These talks may be attended by members and non-members alike as with any technical night.

Please check this page for updates on course locations and times in your city. Some of these talks will talk place over lunch.

The day-long course is aimed at:

• Seismic interpreters who want to extract more information from their data.
• Seismic processors and imagers who want to learn how their efforts impact subtle stratigraphic and fracture plays.
• Sedimentologists, stratigraphers, and structural geologists who use large 3D seismic volumes to interpret their plays within a regional, basin-wide context.
• Reservoir engineers whose work is based on detailed 3D reservoir models and whose data are used to calibrate indirect measures of reservoir permeability.
• Team leaders who wish to identify advances in machine learning technology that promise improved efficiency and accuracy in the integration of large data volumes.

Kurt Marfurt's SEG DISC will tour Australia between 11 and 25 July using the schedule

Please check this page for updates on course locations in your city.

The course is aimed at:

• Seismic interpreters who want to extract more information from their data.
• Seismic processors and imagers who want to learn how their efforts impact subtle stratigraphic and fracture plays.
• Sedimentologists, stratigraphers, and structural geologists who use large 3D seismic volumes to interpret their plays within a regional, basin-wide context.
• Reservoir engineers whose work is based on detailed 3D reservoir models and whose data are used to calibrate indirect measures of reservoir permeability.
• Team leaders who wish to identify advances in machine learning technology that promise improved efficiency and accuracy in the integration of large data volumes.

More course details and registration here.