Application of borehole radar for subsurface physical measurement

Borehole radar is a subsurface detection tool originally designed for imaging geological targets in resistive formations. As the formation becomes conductive, radar becomes ineffective for subsurface imaging because of the high attenuation of electromagnetic waves. In this paper, borehole radar is proven to be capable of measuring the surrounding conductivity and dielectric constant at 60–90 MHz, even in a conductive formation. Although the conductivity measurement is not sensitive, as it is less than 0.001 S m-1, the dielectric constant measurement is sensitive in all, ranging from 5 to 25. In the petroleum industry, these parameters can be used to discern water-bearing or oil-bearing layers even if the formation water is not saline. The vertical resolution of both the conductivity and the dielectric constant are similar to the separation between the two receivers. The measured data exhibit stability and are in good agreement with the borehole television image.