Water Complex Permittivity Model for Dielectric Logging

Abstract

Abstract In recent years, high-frequency dielectric tools have become an increasingly accepted service for providing saturation, water salinity, and textural information. To obtain these petrophysical quantities from the measured dielectric data, a mixing law is used that relates the bulk formation complex permittivity (relative permittivity and conductivity) to the constituents of the system, including the water present in the pores. Several mixing laws have already been published in the literature. This paper is concerned with an integral part of all of them, which is the prediction of the water complex permittivity as a function of salinity, temperature, and pressure. The water complex permittivity is known to vary with salinity, temperature, pressure, and frequency of operation. We have established a dielectric water model as a function of these four quantities, and have recently validated this model with dielectric laboratory experiments on several water samples at high temperature and pressure. In this paper we fully disclose the model so that it can be used and adapted by the industry. We also demonstrate with a sensitivity analysis that using the correct water model is critical to the accuracy of the final petrophysical outputs.