Recovering IP information from broadband EM measurements

Abstract

Fast electromagnetic (EM) inverse techniques can be applied to induced polarization (IP) data, especially when induction effects complicate the interpretation of IP measurements. The EM inverse modeling algorithm automatically compensates for induction effects and can be used to solve for complex conductivity. A synthetic example is initially presented that demonstrates the successful recovery of dispersion information from an interpretation problem containing EM coupling effects. A pole dipole array operating from 0.01 Hz to 10 kHz is chosen as the system to be studied over a layered, conducting earth. The results show the deterioration in sensitivity to deep conductors at higher frequencies over 100Hz. Below this limit relatively good information is recovered. The procedure is found to be relatively insensitive to the amount of regularisation employed to stabilize the inverse problem. It is also noted that good estimates of the dispersion can be made even when the conductivity structure is poorly defined by the inverse modeling.