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Abstract

Two types of dielectric logging tools are in use: the pad type which operates in the 100 to 1100 MHz frequency range and the mandrel type, which typically operates in the 10 to 100 MHz range. Although both types of tools make the same measurement, the lower frequency tools have a greater depth of investigation and therefore have different applications than the higher frequency pad device. However, logs measured with 10 to 100 MHz tools are more difficult to interpret because of the large frequency-dependent dispersion of the dielectric permittivity below 100 MHz. A model of the frequency dependence of the dielectric permittivity has now been developed that predicts permittivities in the 10 to 100 MHz range from the more easily obtained measurements in the 100 to 1300 MHz range. The predicted permittivities are used to calculate fit parameters for interpretation equations normally used for the higher frequency pad devices. Once these fit parameters are known for measurements in the 10 to 100 MHz range, then the high frequency interpretation methods can be applied in the 10 to 100 MHz range. Thus, by combining the model for the frequency dependence of the dielectric permittivity with existing interpretation methods used for 100 to 1100 mHz tools, an improved interpretation of dielectric logging measurements in the 10 to 100 MHz range is possible.

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