Abstract
Laboratory experiment of electrical resistivity measurement using an alternative current (AC) impedance method is important to interpret the electrical survey and logging data, and to understand the electrical properties of rocks and sediments. This study investigated the accuracy and applicability of the AC impedance method by measuring resistors of known resistance (Experiment 1), electrolyte solutions of known resistivity (Experiment 2), and rocks and deep-sea core samples (Experiment 3). We confirmed that the accuracy of the measurement system was the same as that provided by manufacture in the Experiment 1. Two-electrode method was used for the Experiment 2, and the results showed that resistivity and phase angle increased with lowering of frequency and decreasing of the sample resistivity. The resistivity data was more accurate when the phase angle was close to zero. In the Experiment 3, we examined the way to prevent overestimation and underestimation of resistivity by drying and wetting of the sample surface, respectively, and wrapping a sample with parafilm was the most effective. In addition, we measured the samples of various porosity using two- and four-electrode methods. Four-electrode method had an advantage that is applicable to wide range of frequency (102 to 105 Hz) because of its less influence of electrode polarization at low frequency, but reliable data ware also obtained using two-electrode method by measuring highly resistive samples or measuring with high frequency. Our data showed both two- and four-electrode methods were applicable to samples of various porosity (0.3 to 67％).
