Detecting lateral resistivity inhomogeneities with the Schlumberger array[Link]

A method of detecting lateral resistivity inhomogeneities with a multi‐electrode cable for the Schlumberger array is presented. Using such a cable system, two dipole‐dipole soundings are gathered in addition to the Schlumberger sounding at each point. Offset differences calculated from the dipole‐dipole data give qualitative information about lateral resistivity inhomogeneities. Results from 1D modelling can give quantitative information about the 2D resistivity distribution since the dipole‐dipole soundings are made to either side of the Schlumberger sounding point. Examples from two different locations in Norway are shown. At Reinøya, northern Norway, a dipping layer, confirmed by refraction seismic data, was identified. In a sedimentary basin with a contamination plume at Haslemoen, southern Norway, the method has revealed lateral variations in resistivity. In both cases, the Schlumberger soundings could be fitted with a 1D resistivity model.