Abstract:The model experiments showed that the Dias model is suitable for the requirement of IP parameters abstraction of reservoir within the 0.1~300Hz frequency and 1~10km depth ranges in the sounding frequency range of extra-low electromagnetic frequency with larger-power manually-fixed source. Considered the IP parameters of reservoir, there exist obvious abnormalities among the curves of apparent resistivity, apparent resistivity ratio BρT, apparent phase and apparent phase ratio BφT, which showed as follows: ① all BρT abnormal peaks are less than 1, showing that partial separation of proliferated current impedance from polarization impedance of medium and "recognition" of pure DC impedance can be implemented in the sounding frequency range of extra-low electromagnetic frequency with larger-power manually-fixed source; ② there is significant influence of fault-surface type of resistivity on response curves and consistent rule appears in three different depth levels of reservoir (shallow, mid and bottom), for all frequency segments, the frequency descending orders relative to BρT and BφT peaks are A,O,Q, K and H type respectively, among which the peak frequencies in A, O and Q types are higher and the peak frequencies in K and H types are similar to each other and smaller; ③ there is clear positive correlation between abnormal peaks of ratios, their relative frequencies and thickness of oil/gas-bearing polarization bed, which can be used for judging the thickness of polarization bed, and there is correspondent relationship between abnormal peaks of ratios and buried depth of oil/gas-bearing polarization bed, which can be used for judging the buried depth of polarization bed, but it is no easy to judge because there is no clear correspondent relationship between them.