Unique technology and software come together in Kazakhstan: International collaboration for airborne EM

The Story so far …

A recent initiative by Aurora Minerals Group, a company specialising in the transfer of new technologies, and attraction of investment in Kazakhstan for resource and infrastructure developments – has seen to the acquisition of new airborne electromagnetic data in 2016-17, by Danish company SkyTEM™
Originally developed for detection of aquifers, today SkyTEM™ and other similar systems are used for the detection of metallic mineralisation. For both applications, the technology relies on differing conductivities of the target materials, compared to their host rocks in a shallow sub-surface geological setting (less than 600 metres). So, airborne EM data can be used to map the boundaries and faults between the different compositions of rocks and groundwater – even for direct constraint of 3D geology models, with the right software to process the signal.

Introducing the latest software for advanced processing and geological interpretation of airborne electromagnetic data: MOKSHA-EM™ by Intrepid Geophysics

Whist the SkyTEM™ technology normally has a very high signal relative to noise level, interferences such as powerlines (cultural) and induced polarization effects (IP) require careful data processing to clean while retaining as much as the signal as possible. MOKSHA-EM™ a new inversion software code developed in-house by Intrepid Geophysics, Australia (as a proprietary GeoModeller module) - can be used to remove noise and perform high precision 2.5D inversions of the AEM data, as has been demonstrated for the Kurtz survey area, Kazakhstan. 

Figure 1: Kurtz PLNI Monitor: The effect of powerlines is removed prior to 2.5D inversion of the airborne EM signal using MOKSHA-EM™

What are the steps ?

  • The 2.5D inversion system set-up details are entered into MOKSHA-EM™
  • A noise estimation is made
  • Apparent background resistivities are estimated
  • Parameters of the inversion are set, such as: Component and channel selection, multi-threading options, re-sampling and smoothing options, and number of iterations
  • 2D tuning and mesh parameters are set

Inversion results for a single line of the Kurtz survey are shown below (Figure 2).

Figure 2: Top: Inverted profiles over observed profiles for each measurement time with early, mid and late times grouped together in two sets of 3 panels ordered from top (Low Moment component) to bottom (High Moment). Middle: Two panels show the impact of noise thresholding on the Low and High Moments. Bottom 1: the 2.5D inversion log conductivity section with excellent definition of realistic sub-surface geology character, traceable and shown to be at depths up to 200 m below surface – Bottom 2: followed by the same section from the Aarhus Workbench 1D SCI inversion (DOI Masked) which is relatively poorer in terms of providing useful geological knowledge.

Final deliverables were prepared for the Kurtz Project using MOKSHA-EM™ and GeoModeller™ software. These included inversion grids and 3D point meshes. After removing some edge effects from the 3D point mesh, the 2.5D inversion results where interpolated throughout the voxet volume of the 3D subsurface below. Now the 3D Log conductivity FEM point mesh can be shown in a 3D perspective view. These products are ready for geological interpretation or integration with further geophysical data and primary geology observations (drilling or mapping) to constrain the final 3D geology model.  

Figure 3: Kurtz AEM Survey project zone, displayed in GeoModeller™ software – Interpolated Log Conductivity shown as points in a 3D Perspective display – Ready for 3D geological interpretation in GeoModeller™.

The Outcome:
The use of dedicated software MOKSHA-EM™  by Intrepid Geophysics to handle and invert airborne EM data by a 2.5D method, results in the highest possible degree of geological knowledge derived for the shallow sub-surface of the project region.
  • Much higher resolution and more geologically-realistic outcomes than ever possible before, compared with conventional 1D modelling codes or CDIs
  • Handling full survey lines, at least 30 km long
  • Rapid results compared with computational-impractical 3D inversion codes for AEM
  • Practical deliverables from a bureau service

Testimonial: "I'd like to express my satisfaction and gratitude for the professional work completed by Intrepid Geophysics.  In mid 2016 we used SkyTEM from Denmark to complete an airborne time domain electromagnetic survey in North Kazakhstan.  The area surveyed had the added difficulty of a power line running through the area, which can cause interference in the acquisition of the data.  I found Intrepid to be highly professional and knowledgeable with regards to the acquisition, processing and interpretation of geophysical data. I have no doubt that the improved 2.5D inversion code re written and improved by Intrepid is an industry standard when dealing with AEM data.  I have no hesitation in recommending Intrepid to any Exploration or Mining professional". Kent Balas, Chief Geologist, Aurora Minerals Group, Republic of Kazakhstan, January 2017

See news article on the Aurora Mineral Group website

For more information about software products mentioned in this blog: MOKSHA-EM™ or GeoModeller™ developed by Intrepid Geophysics in Australia, please contact sales@intrepid-geophysics.com

For a copy of the Kurtz SkyTEM™ data 2.5D inversion project report – an example of what the Intrepid Geophysics’ AEM Bureau Service can provide, please email helen@intrepid-geophysics.com