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3D Inversion of AEM Data Based on a Hybrid IE-FE Method and the Moving Sensitivity Domain Approach with a Direct SolverNormal access

Authors: L. Cox, M. Endo and M. Zhdanov
Event name: 77th EAGE Conference and Exhibition 2015
Session: Electromagnetic Methods III
Publication date: 01 June 2015
DOI: 10.3997/2214-4609.201413225
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.21Mb )
Price: € 20

Summary:
The moving sensitivity domain method has been very successful in 3D inversion of the data from large airborne EM surveys. The modeling method was based on the integral equation (IE) method. However, in survey areas with rough topography and very high contrast, modelling based on the finite element (FE) method has advantages. We use the combined advantages of the IE and the FE methods in a hybrid scheme with the moving sensitivity domain to create a stable and efficient modeling method. To increase computational efficiency, we have reformulated the moving sensitivity domain so that multiple transmitters are contained in each sensitivity domain. This allows the economical use of a direct solver, because the sensitivity domain’s system matrix can be directly decomposed and then used for multiple transmitter positions. We show that there are an optimal number of transmitters to place in each subdomain: too many and the domain size become unwieldy, too few and the advantages of the direct solver are lost. We apply this technique to data from Germany’s Federal Institute of Geosciences and Natural Resources frequency domain AEM system. We validate the method by comparison with previously published results and our own 1D and 3D inversion results.


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