Cross-hole resistivity tomography using different electrode configurations

This paper investigates the relative merits and effectiveness of cross-hole resistivity tomography using different electrode configurations for four popular electrode arrays: pole-pole, pole-bipole, bipole-pole and bipole-bipole. By examination of two synthetic models (a dipping conductive strip and a dislocated fault), it is shown that besides the popular pole-pole array, some specified three- and four-electrode configurations, such as pole-bipole AM-N, bipole-pole AM-B and bipole-bipole AM-BN with their multispacing cross-hole profiling and scanning surveys, are useful for cross-hole resistivity tomography. These configurations, compared with the pole-pole array, may reduce or eliminate the effect of remote electrodes (systematic error) and yield satisfactory images with 20% noise-contaminated data. It is also shown that the configurations which have either both current electrodes or both potential electrodes in the same borehole, i.e. pole-bipole A-MN, bipole-pole AB-M and bipole-bipole AB-MN, have a singularity problem in data acquizition, namely low readings of the potential or potential difference in cross-hole surveying, so that the data are easily obscured by background noise and yield images inferior to those from other configurations.