Radio-wave detection and estimation of sub-surface hydraulic fractures at MF band

In this paper we present a radio technique for detecting and measuring the extent of hydraulic fractures in subsurface rock layers using MF band. The method is based on transmission measurements among elements of vertical and horizontal arrays in the borehole before and after fracking process. To realize this system a novel super-miniaturized borehole antenna operating at 2MHz is also presented. The proposed antenna is based on a ferrite-loaded helical dipole antenna optimized to fit a volume λ₀/1337 × λ₀/1337 × λ₀/80 while maintain a high radiation efficiency of about 10%.