Experimental study on dielectric spectra of artificial mud cakes and research on dielectric dispersion models

Dielectric logging technology is limited by its shallow probe depth, and the influence of mud cake cannot be ignored. By measuring the dielectric spectrum of 25 artificial mud cakes with different electrical properties, the electrical characteristics and dielectric dispersion model of mud cakes are revealed in this paper. The mud cake was prepared by mixing barite, bentonite, kaolin, sodium chloride and water, and the effect of salinity, clay mineral content and clay mineral type on the electrical properties of the mud cake was studied and discussed by using the terminal open-circuit coaxial reflection method. The experimental results show that in the low frequency band, the dielectric constant of mud cake increases with the increase of montmorillonite proportion, the increase with the increase of clay mineral content and salinity, and the relationship with salinity is linear positive, and the relationship with clay mineral content is more complex, showing a quadratic function increase. In the high frequency band, the dielectric constant increases with the increase of clay mineral content, and is less affected by clay mineral type and salinity. The modified Shaly Sand model (SHSD) dielectric dispersion model can effectively describe this law. The results of this study provide basic data and theoretical basis for environmental correction and forward and inverse research of sweep frequency dielectric logging data.