Experimental study of mechanoelectric transformations in low saturated rocks

Abstract

The results of study of the electrical response of dry and slightly saturated with salted water (NaCl) or kerosene cores of Berea sandstone to acoustic effect in the frequency range of 0.5–10 kHz are presented herein. A strong lateral inhomogeneity by saturation was created during the experiments. The electrical response is sensitive to the addition of all types of fluid in the rock samples. At the same time, the reaction to the addition of highly concentrated salt solution in the samples is weak, while the reaction to the addition of weak concentrated salt solution and kerosene is strong. A high correlation is observed between the shape of the electrical response spectra of dry and damped cores, up to 0.9. For kerosene, the shape of the spectrum varies greatly, the rank correlation coefficient of the shape of the spectra is 0.3. The fact of a significant increase in electrical response on addition of non-polar fluid (kerosene) to the core is beyond the theoretical framework and may be associated with the creation of strong lateral petrophysical heterogeneity by saturation. The strong sensitivity of the amplitude of the electroseismic response of rocks to very weak but non-homogeneous saturation is interesting for the development of remote methods for determination of the type of fluid saturation of rocks, when searching for minerals and for the development of the methods for prediction of geophysical catastrophes.