Dielectric constant measurements of sweep frequency and its effect from 20 MHz to 1000 MHz

Abstract

The array dielectric tool (ADT) can be used in situations where the formation water resistivity is variable or unknown and allows for obtaining Archie's cementation exponent (m) in combination with other porosity logging methods. However, few laboratory measurements of the dielectric dispersion properties at wide frequencies (20 MHz–1000 MHz) have been shown till now, which hinders our understanding of the petrophysical mechanisms. In this study, we introduce the dielectric constant measurements of a sweep frequency in the range of 20–1000 MHz based on the parallel-disk capacitor method. In order to easier control the variables, such as the m and the porosity, artificial cores with changeable m values were manufactured from glass beads. The relationships between the core dielectric constant and the frequency, saturation, salinity, and pore texture were investigated in the MHz to GHz range. It is shown that the frequency, water saturation, salinity, and pore texture affect the dielectric dispersion of cores. Additionally, a modified formula for predicting m with a high-frequency dielectric constant was developed based on core sample data. This study provides a better understanding of the dielectric dispersion mechanism and the modified formula for calculating m can improve the analysis of well log data.