Crosshole electric scanning and profiling of a cylindrical conductor: laboratory investigations

Abstract

A 3-D laboratory tank model system was constructed and used to investigate the crosshole DC electric imaging possibilities of a conductive target using a bipole-bipole array, with one current electrode located in each simulated borehole. Both scanning and profiling measurements were made, for five different classes of cylindrical model, depending on the cylinder orientation relative to the plane of the boreholes and whether the target was continuous, terminating, or broken between the points of measurement, and whether the conductor was intersected by one of both boreholes. Each class of model produces a characteristic response, which can be used to identify the conductor and locate its upper and lower boundaries. Data were collected for different bipole separations. Very clear anomalies are produced for the scanning arrangement (both bipoles moved together) for models involving conductor intersection. Electric profiling, which entails one fixed bipole and one mobile bipole, produces a more subtle but nonetheless diagnostic pattern.