In clay bearing rocks, the presence of a connate brine results in the so-called surface effects: electric double layer polarization (i.e., Stern layer polarization) and Maxwell-Wagner space-charge polarization
. They occur due to the presence of polarizable bound water at the clay-water interface and weakly bounded ions on the surface of mineral particles, which can slowly move under the influence of an external field and contribute toboth the conduction and electric polarization .
In the low-frequency region (f < [10.sup.2] Hz), the dielectric behavior was attributable to the space-charge polarization
. Both frequency-varying [epsilon]' and [epsilon]", dominated by the ionic effect in this frequency region, are proportional to [f.sup.-3/2] and [f.sup.-1] respectively.