Variability of specific electrical resistance in measurements at currents of different frequencies

This paper deals with the results of laboratory experiments aimed at investigating the effect of current frequency on specific electrical resistivity. In measurements by the methods of electrical exploration, resistivity is the main electrophysical characteristic of a medium both on direct and alternating current. In practice, when solving inverse problems, geophysicists often incorrectly correlate resistivity values measured by the res istivity methods with the results of the highfrequency electromagnetic methods, which leads to the construction of obviously erroneous physical-and-geological models and petrophysical relations. Experimental and methodological electrical exploration works confirm the dependence of electrophysical properties of rocks on the current frequency and serve as a basis for the construction of probabilistic regression equations. However, the small number of laboratory studies on the frequency dispersion of electrophysical parameters of rocks disallow the statistical analysis of the data, including the methods of regression and correlation analysis. To investigate the frequency dispersion of resistivity of different genesis samples, and to confirm or supplement the already known empirical functional relationships, experimental laboratory measurements were made at the Exploration Geophysics Laboratory at the Empress Catherine II St. Petersburg Mining University using the device PetrOhm for measuring the electrical properties of rocks. Cylindrical rock samples of different genetic type and electrical conductivity were prepared for measuring electrical resistance as a function of current frequency. As a result, the qualitative and quantitative relations are obtained for the studied samples with the total value of approximation reliability mostly more than 0.97, which allows using the obtained dependences for constructing the models of geoelectric sections based on the results of AC measurements and classical resistivity methods.