Video: Dielectric Constant Interpretation: Comparison of the Salinity Dependence of the Real and Imaginary Response
- Michael Myers (University of Houston)
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- Society of Petroleum Engineers
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- 2019. Copyright is retained by the author. This presentation is distributed by SPE with the permission of the author. Contact the author for permission to use material from this video.
- Shaly Sands, Dielectric Constant, Salinity Dependence
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In this paper the dielectric constant of shaly sands both the real and imaginary parts is investigated and compared. An empirical model has been developed in the one MHz to one GHz frequency range for the real part of the dielectric constant. The equations developed involve the same pore systems as those governing the conductivity response. The dielectric constant contains an additionalfrequency independent high frequency limit. The dispersive terms are due to the clays and interfacial phenomena. The salinity and frequency dependence of these parameters are then discussed.
This salinity dependence of the dielectric model is compared to the salinity dependence both predicted and measured for the conductivity. Conductive inclusions are modeled similar to previously published work (Myers 1989) The Hanai-Bruggeman equation plays the central role which is consistent with Archie's equation but allows for conductive inclusions. The model for dispersed clays incorporates the effects of clay geometry and demonstrates that the conductivity is intimately related to the geometry and length scales involved in the clay conduction. The increase in the effective clay-counter ion mobility with increasing salinity is due to the coupling between the conductivity of the clays and the conductivity of the brine. It also demonstrates that the shape of the conductivity curve depends on the ratio of intergranular to clay porosity.