The frequency dependence of complex electrical conductivity in the frequency range from 10~(-3)to lo3 Hertz has been investigated for a variety of microcracked rocks from the German continental deep drilling project(KTB),Northern Bavaria.The laboratory measurements were made with a computer controlled four-electrode system on plugs saturated with brine of different salinity.It has been found that the complex electrical conductivity may be described using well kmown models applied for shaly sands.The main feature of the conductivity spectra is a constant phase angle over the investigated frequency range combined with a nearly identical power law frequency dependence of the real as well as the imagmary parts.The results of the study show that complex electrical parameters dependent on(1)the crack porosity and surface area to porosity ratio,(2)the conductivity and other properties of the crack filling water,and(3)orientation and genesis of the nlicrocrack network.Complex conductivity measurements allow an uncomplicated separation of electrical volume and interface effects.Moreover,the results suggest that determination of specific surface area and other rnicrocrack network characteristics of crystalline rocks directly from complex electrical measurements can be made.
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