Novel Application of Multifrequency Dielectric Technique for Hydraulic Fracture Characterization in Different Rock Formations

The multifrequency dielectric technique has emerged as a promising petrophysical tool for estimating water saturation and calibrating Archie parameters, with growing potential for fracture characterization. However, most previous studies in this area have focused on numerical models or synthetic systems. This study presents a novel experimental approach for characterizing hydraulic fractures in sandstone and carbonate formations using multifrequency dielectric measurements under both dry and brine-saturated conditions. Rock samples were subjected to routine core analysis to determine porosity, permeability, and mineralogy. Nuclear Magnetic Resonance (NMR) was employed to assess pore systems and porosity distribution. An open-ended coaxial dielectric probe, operating between 1 MHz and 3 GHz, was used to measure relative permittivity and electrical conductivity before and after inducing hydraulic fractures with controlled vertical and horizontal orientations. Measurements were taken at various distances from the fracture (near and far) and under dry and brine-saturated states using 3 wt.% KCl brine. The results demonstrate that dielectric dispersion is highly sensitive to fracture presence and geometry. The permittivity was increased by 22 units on average, from around 45 to more than 60 for carbonate rocks, while the increase varied between 15 and 35 units for sandstone rocks. Also, measurements taken near the fracture showed stronger dielectric responses due to enhanced fluid connectivity and polarization effects. The conductivity increased by around 12 to 34% in fractured carbonate and sandstone samples, respectively. Fracture orientation had a notable impact, with vertical fractures producing relatively higher conductivity and permittivity compared to horizontal fractures. In contrast, NMR was unable to distinguish fracture orientation due to its bulk measurement nature. This study establishes a robust and experimentally validated method for characterizing hydraulic fractures using multifrequency dielectric measurements. The approach offers enhanced resolution of fracture orientation, connectivity, and localization, with significant implications for both conventional and unconventional reservoir development.