Interpretation and removal of EM coupling in IP data

Abstract

We have computed EM coupling responses for the dipole-dipole IP array over realistic 3-D bodies using a volume integral equation approach. The objectives of these simulations are to gain insight regarding negative EM coupling over good conductors, to analyze the phase extrapolation method of removing EM coupling, and to determine whether interpretation of the EM coupling can help resolve the resistivity structure. Our results show that a good conductor, especially if it is shallow, can produce a complex pattern of negative and positive coupling in a pseudosection. Extrapolating three-frequency phase data to zero frequency eliminates EM coupling in most cases; however, residual EM effects may be present in extremely low-resistivity environments. We are studying ways of utilizing EM coupling to provide information about 3-D bodies beyond that produced by DC resistivity data.