Relationship between Surface Conductivity and Induced Polarisation Parameters
A. Weller, L. Slater and S. Nordsiek
Event name: Near Surface Geoscience 2013 - 19th EAGE European Meeting of Environmental and Engineering Geophysics
Session: Laboratory Studies of Soil and Rock Physics
Publication date: 09 September 2013
Info: Extended abstract, PDF ( 285.39Kb )
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Interpretation of resistivity measurements is often uncertain as resistivity is controlled by pore fluid chemistry, moisture content and lithology. Induced polarisation measurements may help to reduce this uncertainty as they are primarily controlled by lithology and, relative to resistivity measurements, weakly dependent on pore fluid chemistry. In order to exploit this potential, we have investigated the relationship between the surface conductivity appearing in petrophysical models for resistivity and the imaginary conductivity measured with induced polarisation. It has previously been suggested that imaginary conductivity can be used to estimate the surface conductivity if the ratio of surface polarisation to surface conduction (l) is known. However, a detailed investigation of this ratio has not hitherto been reported. We performed a study on an extensive database of sandstone and unconsolidated samples where resistivity and induced polarisation measurements were acquired as a function of salinity. The surface conductivity was estimated assuming a simple parallel conduction model where conduction through interconnected pores and conduction along interconnected pore surfaces add in parallel. The surface conductivity exhibits a weak salinity dependence that is similar in shape to the salinity dependence of the imaginary conductivity. This finding suggests that l is only weakly dependent on salinity.