Permittivity measurements of artificial sediment with high conductivity using open-ended coaxial probe

Abstract

Microwave dielectric properties serve as critical diagnostic parameters in geophysical studies, enabling quantitative evaluation of factors such as water saturation and matrix structure. Open-ended coaxial probes (OCP) are widely used for broadband microwave dielectric measurements in highly mineralized loose geophysical sample like soil, sediments etc., where electrode polarization (EP) effects severely degrade measurement accuracy and obscure the Maxwell-Wagner (M-W) polarization near the lower frequency limit of OCP. Notably, the EP effect is highly sensitive to the electrode surface, and variations in the measurement process can significantly impact the accuracy of the EP correction model. To address these issues, this study proposes an optimized EP correction method based on the constant phase angle element (CPE) model. By calibrating with brine of the same conductivity as the sample after the initial measurement, consistency in electrode surface and conductivity conditions is ensured. This study establishes a transfer mechanism between the two scenarios, effectively removing EP's impact on complex permittivity measurements below several hundred MHz in highly mineralized sediment. Experimental results on artificial sediments revealed that M-W polarization strength increases with decreasing sand particle size, and with increasing brine mineralization and saturation. Additionally, clays with high cation exchange capacity enhance dispersion below 100 MHz and shift it to higher frequency. Further measurements on hydrate reservoir marine sediment confirm the method's effectiveness in complex natural samples. By eliminating the interference of EP, this study provides a reliable solution for accurate dielectric measurements in highly mineralized sediment, offering significant value for investigating seafloor sediments and soils.