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The geo-electric method allows mapping of resistivity and induced polarization effects in the subsurface. It permits detection of diagenetic alteration zones with micro-pyrite crystals, situated some distance above hydrocarbon accumulations due to leakage from a non-perfect top seal. Geo-electric surveying (DNME) uses special parameters for monitoring the electric earth response in time. Inversion of relaxation curves is done to establish a depth model, whereby non-uniqueness of the solution is a well known problem. Additional constraints are needed for a plausible scenario. Two basic components are measured: the electromagnetic and induced polarisation response. A synthetic model illustrates their contributions in spite of the non additive character. The inversion is done in a 1D mode with a Cole-Cole simulation. The modelled response at a recording station has been compared with that of the known 3D model. The discrepancy is better than 0.1 %, illustrating the validity of the inversion modelling. A considerable amount of successful study cases has been performed in Russia, like the Severo Guljaevskaya study in the Barents Sea. The geo-electric technique reduces risks attached to drilling of new hydrocarbon prospects and provides a better ranking at a reasonable cost.

—The paper considers the manifestation of electromagnetic (EM) signal over the conducting polarizable ground on the measuring lines located on the axis of the source and inside it (for the symmetric Schlumberger installation). The research is based on a numerical experiment. Calculations of the EM response from one-dimensional models were carried out. The polarizability is taken into account by the frequency-dependent resistivity, using the Cole-Cole model. We describe the results of a numerical experiment on calculation of the induction signal over a conductive polarizable medium on grounded 2- and 3-electrode measuring lines located in the axial and equatorial zones of the source. It is shown that the induced polarization and the polarization associated with galvanic and eddy current are manifested in different ways.

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