Experimental data for the real part of the dielectric constant (K') of three sandstone samples are considered as a function of the level of water saturation (S w ) in the frequency range 60 kHz to 4 MHz. Existing theoretical models have previously shown poor agreement with K' versus S w data for rock samples, undoubtedly due to the complexity involved in adequately accounting for geometrical and electrochemical effects. In analyzing the data presented here, we find a pronounced increase in K' in the low saturation region which in all cases can be attributed to the establishment of geometrical and surface effects associated with the rock-water interface. When this increase in K' is accounted for by defining wetted matrix parameters, the data show excellent agreement with existing theoretical models.

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