Uniaxial Complex Relative Permittivity Tensor Measurement of Rocks From 40 Hz to 4.5 GHz

We develop a set of combined measurement techniques and calculation workflows to determine the complex uniaxial dielectric tensor of a rock sample from 40 Hz to 4.5 GHz. This unique method provides the ability to develop interpretation models bridging electrical logging tools with their corresponding operational frequencies and measurement direction. It further highlights the presence and importance of accounting for electrical anisotropy dispersion in formation evaluation. This permits the industry to initiate the desired electrical logging programs and apply appropriate borehole raw data corrections. The required workflow utilizes three measurement systems, which when combined result in measuring the electrical dispersion over a broad frequency range in the radial and axial directions on the same vertical rock sample. The measurement process is grouped into a high-frequency device from 10 MHz to 4.5 GHz and a low-frequency system from 40 Hz to 100 MHz. The high frequency is a two-port coax to circular waveguide and is described in this paper for measuring broadband data of dielectric dispersion properties of reservoir rocks in both anisotropic directions. The low frequency consists of combining both parallel plate capacitor and one-port coax with a circular waveguide terminated by a short (0 Ω) or open (infinite ohms) to obtain dispersion curves in both the axial and radial directions. The theoretical basis of each of the above systems is described. Two reservoir rocks are tested and their results are reported. In conclusion, the added value this laboratory capability presents will yield a higher quality of borehole data and a more quantitatively accurate petrophysical interpretation.