MECHANISMS OF INDUCED POLARIZATION IN ELECTRON-CONDUCTING MINERAL INCLUSIONS WITHIN ROCKS: RESULTS OF LABORATORY STUDIES
G.V. Gurin
OOO NPP VIRG-Rudgeofizika, St. Petersburg, Russia
Keywords: Induced polarization, rock polarization mechanism, rock polarization model, steady-state polarizability, interfacial electric potential
Abstract
The unique relationship between induced polarization parameters and the structure of interface and pore space in rocks sustains considerable interest in applied science, driving the continuously expanding range of application of this method. The physicochemical theory of induced polarization in rocks contains significant gaps, which stem from the complexity of the processes generating secondary electric fields within rocks. To date, laboratory investigation results remain the primary source of new knowledge about the mechanisms and processes occurring in rocks under the influence of an electric field. Over the past decade, several new hypotheses, mechanisms, and models of induced polarization in rocks containing electron-conducting mineral inclusions have been proposed; their key features are described in our article. These hypotheses are actively discussed and used for interpreting induced polarization data obtained in laboratory studies and field tests. We present the results of an experimental study of induced polarization at the shungite - pore moisture interface, conducted on a synthetic capillary model of rocks containing an electron-conducting mineral inclusion. Based on voltammetric measurements, the principal characteristics of shungite polarization in an aqueous NaCl solution are established. The magnitude of exchange currents, the dynamics of interfacial polarization at different current densities, and the features of interfacial potential relaxation are estimated. Our study features the first presentation of measurements of electric currents flowing within the model and inside the shungite inclusion - the induced polarization currents. It is proven that the relaxation of the electric field in the model and that of the induced polarization currents exhibit identical dependences. The proportionality between the polarization intensity of the shungite inclusion and the normal current component at the shungite - pore moisture interface is experimentally confirmed. The resulting materials point to the dominant role of the electrode polarization mechanism for electron-conducting mineral inclusions in rocks. A description of the most probable induced polarization mechanism at the mineral inclusion - pore moisture interface in rocks is provided.
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