Multi-EMMulti-Method Inversion to Determine the ElectricalConductivity Distribution of the Subsurface Using Parallel Computing Architectures

Multi-EM

SummaryElectromagnetic (EM) techniques are nowadays routinely used ingeodynamic research or to characterize hydrocarbon reservoirsin offshore petroleum exploration. Moreover, distinct electricalconductivity properties make EM techniques prime geophysicaltools to characterize saline aquifers for geothermal reservoirs orCO2 storage. Still, the interpretation techniques need to be im-proved. With the Multi-EM project we attempt to enhance resolu-tion properties by combining quasi-static geoelectric potentialfield and electromagnetic diffusion methods in a multi-scale en-vironment. This collaborative effort combines research groupsfrom applied and numerical geophysics, information technologyand numerical mathematics.

IntroductionThe electrical conductivity of the subsurface can be explored usinga variety of techniques. Here, we focus on the DC resistivity me-thod, transient electromagnetics (TEM), natural source magne-totellurics (MT) and controlled source electromagnetics (CSEM).The resolution power of the individual method depends on the ex-perimental design, the strength, geometry, and signature of thesource field, and the characteristics of the subsurface current sy-stem. The table below compiles the pros and cons of each methodalong with typical application areas to show the diversity of EMexploration.

Multi-method, multi-scale, multi-dimensional inversion

Joint multi-scale multi-method EM inversion strategies aim atcombining the strengths of different methods to obtain enhancedresolution power. The combination of various sensitivity patternsis expected to result in (i) better coverage of the model space (ii)more complete and better resolved reconstructions of the sub-surface conductivity structure and (iii) reduction of model ambi-guities.Considering the enormous numerical complexity of multi-methodthree-dimensional inversion, the new algorithms are designed forparallel computing architectures integrating memory and run-time efficient state-of-the-art numerical simulation techniques.

Synthetic experiment

a) ”True model” b) MT resolves the conductive parts (red) but failsto image the thin resistive (blue) sheet c) CSEM can resolve resistivestructures better, whereas conductor is not well resolved d) Jointinversion combines the advantages of the individual methods andresults in a model close to the “True model”.

Contact personResearch project Multi-EM

Dr. Oliver Rittertelephone +49 (0331) 28812 57oliver.ritter@gfz-potsdam.de

Prof. Klaus Spitzertelephone +49 (03731) 392722

klaus.spitzer@geophysik.tu-freiberg.de

Coordination office GEOTECHNOLOGIENAlexandra Scherer

telephone +49 (331) 288-1074 kontakt@geotechmarket.de

www.geotechmarket.de

Technological potential and advantages:

- High-resolution electrical image of the subsurface- Variety of geoengineering and geoscientific applications- Cost effective subsurface imaging- Complementary to seismic exploration techniques

Inquiry for cooperation:

The field of application is not restricted. The multi-scale approachoffers a wide range of possibilities even outside geo-related fields.For further questions, please feel free to contact us.

The project Multi-EM was supported by the GEOTECHNOLOGIEN program of the Federal Ministry of Education and Research.