长7段油页岩复电阻率频散特征及温度敏感性分析OA

As an unconventional oil and gas resource with huge reserves,oil shale has attracted much attention.Studying the frequency dispersion and temperature sensitivity of the complex resistivity of oil shale is conducive to deepening the exploration and in-situ heating recovery technology of oil shale.In this study,experiments are conducted by sealing with soft silicone and heating in a water bath to measure the impedance spectra of the Chang7 oil shale in the temperature range of 25～95℃and the frequency range of 4 Hz～5 MHz.The experimental data are fitted with the second-order Cole-Cole model,and a systematic study is carried out on the parameter sensitivity and the influence of temperature on the complex resistivity characteristics.The results show that:① The complex resistivity dispersion of oil shale shows a dual polarization mechanism.The real part of the resistivity decreases stepwise with multiple slopes as the frequency increases,and the imaginary part of the resistivity shows a double-peak evolution characteristic.② The increase in temperature leads to an increase in ion mobility,a shortening of polarization relaxation time,and a weakening of energy dissipation.The absolute values of the real and imaginary parts of the complex resistivity decrease overall,and both the first polarization frequency and the interface polarization frequency increase exponentially with temperature.③ The first-order derivative of the real part of the resistivity with respect to the logarithm of the frequency is highly correlated with the imaginary part of the resistivity.The attenuation rate of the real part of the resistivity is the fastest when the polarization intensity is the highest.④ The determination coefficient R2 of the second-order Cole-Cole model fitting is generally higher than 0.98.The zero-frequency resistivity and relaxation time in the model parameters decrease significantly with increasing temperature,the polarization rate decreases in the high-temperature section,and the frequency coefficient fluctuates with temperature.The conclusion is that the second-order Cole-Cole model can effectively describe the dual polarization characteristics of oil shale.The research results deepen the understanding of the coupling relationship between the electrical properties of oil shale and temperature,and can provide a reference for the geophysical exploration and development of oil shale.