The measurement and interpretation of EM impedance data at frequencies up to 100 kHz

Abstract

Wide frequency range complex impedance measurements obtained with new RAS-1 field equipment, reveals the ground response near a dipole energy source after the reduction of coupling and other measurement errors to insignificant magnitudes. The observed field impedance data has been modelled by the radial and tangential electric fields of a radiating dipole in full-space. Qualitative agreement is obtained for the amplitude measurements up the medium frequency range with qualitative agreement of the phase. Good values of the IP and conductivity can be obtained, and since the position of the attenuation is sensitive to small permeability changes, permeability will be a measureable quantity in many geological environments and may be very prominent in association with mineralization. Permittivity is measureable in more resistive environments at high frequencies. The availability of more accurate measurements is a prerequisite to the use of more refined models of the source and the half-space, taking into account the complex nature of the conductivity, permeability and permittivity, for the purpose of more accurate delineation of inhomogeneities in the ground.