Open AccessElectrical spectroscopy of porous rocks: a review—II. Experimental results and interpretation
Author(s) -
Chelidze T. L.,
Gueguen Y.,
Ruffet C.
Publication year - 1999
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.1999.00800.x
Subject(s) - dielectric , permittivity , polarization (electrochemistry) , porosity , induced polarization , materials science , mineralogy , condensed matter physics , electrical resistivity and conductivity , surface area to volume ratio , surface conductivity , porous medium , surface layer , electric field , conductivity , chemistry , physics , composite material , thermodynamics , layer (electronics) , optoelectronics , quantum mechanics
In the frequency range from millihertz to hundreds of megahertz, many different physical and physico‐chemical processes contribute to the electrical polarization of porous water‐bearing rocks. This makes the interpretation of their electrical spectra a complicated problem and requires both elaborate theories and model experiments. At high frequencies, the Maxwell–Wagner–Bruggeman–Hanai (MWBH) theory of effective media, which takes into account only bulk properties, shape and partial volume of components, is very appropriate. At low frequencies, surface films, polarization of the electrical double layer (EDL) and clustering of conductive components can produce very strong polarization; corresponding theoretical models are considered in a companion paper (Chelidze & Gueguen 1999, hereafter referred to as Paper I). This paper is devoted to the review of experimental data and their comparison with theoretical models. Experiments on saturated mineral powders and rocks with various surface areas and surface chemistries confirm the existence of significant surface contributions to the electrical spectra of conductivity and polarization of water‐bearing rocks and the dominance of this contribution over MWBH values at low frequencies. The effective dielectric constant of porous saturated rocks increases with the surface‐to‐volume ratio of the system and strongly depends on the surface charge ( ζ potential). At ζ potential, equal to zero, the low‐frequency dielectric permittivity (DP) is minimal. The experimental data on relaxation times and the magnitude of the surface polarization of water‐bearing porous systems can be satisfactorily explained by theories of film polarization, diffusional polarization generated by deformation of an ‘open’ electrical double layer (EDL) and percolation.