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Interpretation of geoelectric measurements

Class at Faculty of Science |
MG452P64

Syllabus

1. Direct inversion of resistivity sounding curves - downward transformation, resistivity gradient medium. Multilayer model - Zohdy`s algorithm. Influence of 2D inhomogeneities in resistivity sounding.

2. 2D modelling in resistivity method - principle of direct problem, RES2DMOD program, computations for various electrode arrays and models. Principle of 2D inversion - interpretation of multielectrode surface measurements, borehole-borehole and borehole-surface-borehole measurements, processing of field data.

3. Direct problem (1D) in magnetotelluric sounding, approximate inversion - Bostick`s transformation and its practical realization.

4. Interpretation in VLF-R method - E-polarization, H-polarization, model curves, interpretation in two-layer case. Inductive variant of VLF method - analysis of model curves with respect to overburden, conductive and geometric factors, response of surface inhomogeneities. Program VLFMOD - practical usage.

5. Shallow EM profiling - conductivity meters (e.g. EM-31), orientation of dipoles, methodics of measurement, response of typical 2D structures, approximate 1D forward problem, comparison with resistivity sounding.

6. Transient sounding (near zone) - data processing, transformation of measured voltage to H-component and apparent resistivity (asymptotic and full formula), approximate direct inversion (halfspace model, thin sheet model).

7. Electrical properties of rocks in time-varying EM field - wave number and related parameters, frequency dispersion of permittivity and conductivity, effective parameters, limit cases, georadar frequency band.

8. Georadar - reflection and refraction of EM plane wave, characteristics of georadar systém, radiation pattern of electric dipole, main wave types, resolving capabilities, methodics of measurement (sounding, profiling).

9. Airborne EM methods - principles, geometry of basic systems (active, passive), time domain and frequency domain methods. Borehole EM methods - basic variants, transmitters, receivers, methodics of measurements.

10. Principles of some non-traditional or new geoelectrical methods - e.g. magnetic resistivity method, time domain reflectometry (TDR), metal detectors, surface nuclear magnetic resonance method (NMR).

Annotation

Direct inversion of resistivity sounding curves, multilayer model. 2D modelling in resistivity method, principle of 2D inversion. Direct 1D problem in MT, approximate inversion.

Interpre-tation in VLF method, program VLFMOD. Shallow EM profiling.

Interpretation procedures in transient sounding (near zone). Electrical properties of rocks in time-varying EM field, geora-dar.

Airborne EM methods, borehole EM methods. Principles of some non-traditional or new geoelectrical methods.