Inductive interaction between closely spaced steeply dipping tabular conductors located in a resistive host

Physical scale-model studies of the responses provided by horizontal coplan ar and vertical coincident coil moving-source electromagnetic systems when operated over closely spaced, steeply dipping, tabular conductors located i n a resistive host are presented. For separations of the conductors that pe rmit separate anomalies to be identified, the detected effect of inductive interaction between the conductors depends on the configuration of the expl oration device. As conductors are moved closer together, the horizontal cop lanar coil system produces responses for each conductor that become progres sively weaker than the individual responses when each conductor is isolated . By comparison, vertical coincident coils detect an initial increase of th e anomalies from the individual conductors as the conductor separation is r educed until just before the separate anomalies merge. As the anomalies mer ge, the vertical coincident coil responses decline in magnitude. After the anomalies merge and present the appearance of the response of a single cond uctor, both coil systems record an expected strong increase of response whi ch exceeds the response when the conductors are in contact. These mutual in ductive interactions cause significant variations in the depth estimates pr ovided by horizontal coplanar coils. Depth estimates provided by vertical c oincident coils are always smaller than the true target depths. The vertica l coincident coil configuration displays an ability to identify separate co nductors at significantly smaller conductor separations than can the horizo ntal coplanar coils.