Effects of surface conductors on the TEM late-time apparent resistivity

Summary For the central-loop induction TEM (transient electromagnetic) method, the effects of surface conductors on the late-time apparent resistivity are investigated. These conductors can be pipelines, power lines, railroad tracks, fences, brine ponds, etc. In this paper, two cases are investigated through numerical simulations: a long, linear conductor parallel to one edge of a square transmitting loop, and a short, linear conductor inside and crossing the edge and outside of the square transmitting loop. These conductors are in contact with the earth over their entire length. This work focuses on the computational simulation of TEM responses for these types of conductors. The TEM responses are calculated using a 3D finite-difference timedomain electromagnetic code. Results of the 3D TEM simulations show that care must be exercised in interpreting the TEM responses in the presence of surface conductors.