Three-dimensional modeling of frequency- and time-domain electromagnetic methods with induced polarization effects

• Published in: Computers & geosciences 2019-03, Vol.124, p.85-92
• Main Authors: Qi, Youzheng, El-Kaliouby, Hesham, Revil, André, Soueid Ahmed, Abdellahi, Ghorbani, Ahmad, Li, Jianhui
• Format: Article
• Language: English
• Subjects: 3D electromagnetic modeling; Earth Sciences; Finite element; Frequency-domain electromagnetic method (FDEM); Geophysics; Induced polarization (IP); Sciences of the Universe; Transient electromagnetic method (TEM)
• ISSN: 0098-3004; 1873-7803
• DOI: 10.1016/j.cageo.2018.12.011

Electrical conduction describes the ability of porous media to conduct electrical charges and induced polarization (IP) describes their ability to reversibly store electrical charges. An effective conductivity can be defined as a complex number with frequency-dependent components (i.e., the conductivity is also dispersive). Although IP effects have been observed in frequency- and time-domain electromagnetic (FDEM and TDEM, respectively) data for years, most FDEM and TDEM studies still treat the earth using the conductivity alone (therefore neglecting IP effects). Electromagnetic field data inversion and interpretation require a quantitative three-dimensional modeling with dispersive conductivities, which is still a challenging problem. Using the generic partial-differential-equation solver Comsol Multiphysics's application program interface (API) with Matlab, we have successfully developed three-dimensional FDEM and TDEM modeling with IP effects. Benchmarks are performed using analytical solutions and other numerical techniques. Results with and without IP effects are also compared and analyzed to illustrate the importance of taking IP effects into account. Our modeling could be of great importance in quantitatively studying IP effects in the FDEM and TDEM methods, in developing new field configurations, and also in educational purposes. •3D EM modeling with induced polarization effect both in frequency and time domains.•Induced polarization makes the earth conductivity become frequency-dependent.•Fast cosine transform is used to solve the convolution problem in time-domain.•Sign reversal can happen in time-domain EM response for the polarizable earth.•Analyses show induced polarization effect can play an important role in EM response.