Resistivity of granite and sandstone varies with frequency and water saturation

Exploring the effects of excitation polarization and moisture saturation on rock resistivity is crucial for evaluating resistivity-related technologies and engineering, such as electrical exploration. This study selected granite and sandstone from Shandong and Wanzhou to evaluate the rock resistivity at various frequencies (0.1 ~ 200 kHz) and saturations (0 ~ 100%). Under conditions of low saturation of granite and sandstone, the results indicate that the resistivity of the rock sample will rise with increasing saturation due to the excitation polarization effect. As the saturation corresponding to the peak resistivity is approached, the influence of pore water on resistivity replaces the primary role of the excitation polarization effect, resulting in a fall in the resistivity of the rock sample with the increase in saturation. Furthermore, the exponential function relationship between peak saturation and frequency is positively correlated, and peak saturation increases rapidly with increasing frequency due to the disappearance of interface polarization at 104 ~ 105 Hz, with an increase of about 60%.