Can Accurate Estimates Of Permeability Be Obtained From Measurements Of Dielectric Properties?

A laboratory study was conducted to investigate relationships between dielectric properties and hydraulic<br>permeability of sand-clay mixtures. The mixtures were generated in such a way as to vary systematically parameters<br>such as porosity, clay volume fraction and specific surface. Each of these parameters affects both dielectric properties<br>and permeability. For each mixture, measurements were made of porosity, clay content, permeability and dielectric<br>constant at two levels of water saturation (room dry and fully saturated). For the suite of mixtures generated,<br>porosity ranges from 0.240 to 0.605, clay content ranges from 0.000 to 1.000, and permeability ranges from<br>5.3~10~‘~ to 2.7~10~~ cm2. At a frequency of 1 MHz, the dielectric constant ranges from 3.54 (dry quartz sand) to<br>49.4 (saturated kaolinite clay). Crossplots are used to investigate relationships between various parameters. Results<br>show that many relationships such as porosity-permeability and dielectric constant-permeability are multivalued and<br>involve critical points or minima in some parameter. In addition, the experimental data are compared to predictions<br>from three interrelated petrophysical models: (1) a microgeometrical model which describes the relationship between<br>porosity and clay content in sand-clay mixtures, (2) a permeability model based on the Kozeny-Carmen equation, and<br>(3) a dielectric model which incorporates geometric information through the use of wetted matrix parameters.<br>Results show excellent agreement between predicted and observed data. At least for these mixtures, permeability<br>estimates accurate to within an order of magnitude may indeed be derived from dielectric measurements. Such<br>petrophysical relationships can be used in ground penetrating radar and very early time electromagnetic surveys to<br>estimate permeability values and connectivity functions in the field.