Despite its variable nature, the electrical and magnetic induced polarization of rocks in the presence of alternating current phenomenologically manifests itself as an electromagnetic (EM) process. Geophysicists have come to this conclusion in a stepwise manner through the development of the transient EM method (TEM) or transient sounding method, especially in the near zone. As will be discussed, the special role of the combined transmitter and receiver loops configuration used in this method is notable in that the induction signal generated with this construction is always positive. Studying the causes of a sign change in an experimentally observed signal resulted in the determination of the influence of electrical induced polarization (IP).
The suggested work content includes the phenomenological theory of electromagnetic field in polarizable media, as well as the separation description of induction and polarization fields on the basis of mathematical modeling and field experiments.
As a probable cause for a transient process sign change observed in combined loops, the IP influence was first mentioned in the introduction to “The manual for TEM application in mining geophysics” [a group of authors, edited by Kamenetsky, 1976]. Significant contributions to the study of the IP effect as an EM phenomenon have been made by many Russian and foreign geophysicists: Barsukov, Fainberg, 2002; Chernyshev, Trigubovich, 2012; Daev, Talalov, 1996; Dias, 2000; Gubatenko, 1991; Kamenetskaya, 1968; Kamenersky, 1997; Kamenetsky, Timofeev, 1984; Kamenetsky, Stettler, Trigubovich, 2010; Kormiltsev, 1981; Kormiltsev, Mezentsev,1989; Kozhevnikov, 1990; Krylov, Bobrov, 1997; Lee, 1981; Sidorov, Yakhin, 1979; Sheinmann, 1969; Svetov, 2008; Tabarovsky, Epov, 1990; Trigubovich, Epov, 1997; Trigubovich, Persova, Soloveychik, 2009; Van’yan, 1997; Wait, 1959; Weidelt, 1982; Zhdanov, 2008, 2009, 2012, among others.
To solve the direct and inverse problems of modern EM prospecting, a general phenomenological theory of EM field in a polarizable-dispersive geological medium (GPhT for short) covering all possible types of rocks, including homogeneous types, is required. The EM properties (conductivity , permittivity and magnetic permeability ) of this medium depend on transient time and field frequency in the time and frequency domains, respectively.
The previously relied-upon EM sounding theory does not take into account the above phenomena. In this case, the data inversion leads to distorted information about the properties of the medium in question, which can lead to an incorrect further interpretation.
GPhT-based data inversion makes the following possible:
- diagnosing the polarization-dispersion influence,
- determining the true (non-distorted) EM properties of a medium,
- defining the polarization-dispersion response separately, which can yield additional useful information in applying the geological interpretation.
The theory described below develops the ideas of S. М. Sheinmann  and, particularly, V. V. Kormiltsev , who was the first to introduce polarizability into electrodynamic equations. We have further developed this approach into the most generic formulation possible, where nothing is postulated a priori except the dependence of the medium’s EM properties on the transient time or the EM field frequency. Similar to many other researchers, we have used the well-known Cole-Cole formula to describe the dependency mentioned above. The rigorous proof of the applicability of this formula can be found in the work of M. S. Zhdanov .