Influence of the wettability on the electrical response of microporous systems

The permittivity of different microporous systems, including sintered glass filters, Berea sandstones and reservoir rocks, was measured in the frequen cy range 10(2)-10(10) Hz. For each system, the natural pore wettability was modified to get two different sets of samples: those strongly oil-wet and those water-wet. The samples were saturated with a hydrocarbon oil and wate r at different degrees of water content. Dielectric spectra showed a conduc tivity contribution due to ionic carriers in addition to a Maxwell-Wagner-S illars relaxation, active up to high frequencies. Because of the dominant r ole that wettability plays in the electrical response of partially saturate d microporous solids, water-wet and oil-wet samples showed remarkable diffe rences in the loss tangent spectra, as well as different times and strength s of the Maxwell-Wagner-Sillars relaxation. The dielectric spectra were ana lysed by using some standard models for extracting valuable information abo ut the pore wettability. Moreover, the use of impedance measurements for in situ determination of the wettability of reservoir rocks was evaluated.