The features of numerical VEMKZ data interpretation in deviated and horizontal wells entering oil-saturated and water-saturated formations are observed. On the basis of mathematical modeling of VEMKZ signals for typical hole path of horizontal wells the effects caused by crossing bed boundaries and thin layers with high resistivity are shown. The influence of electrical anisotropy on signals has been investigated. The influence of borehole rugosities and tool eccentricity was studied. The programs of numerical modeling have been developed at Institute of Petroleum Geology and Geophysics (IPGG) Siberian Branch of Russian Academy of Sciences. Algorithms and methodological procedures are used for numerical interpretation of VEMKZ data (including SKL set data) in case of thin reservoir, electrically contrasting shoulder beds and thin interlayers. The eccentricity, borehole rugosity, sine-shaped and spiral well bore influence on signals was investigated in case of typical hole and tool diameters, the programs of numerical correction have been developed. The fact that influence of electrical anisotropy in deviated well causes apparent resistivity increase is demonstrated. Numerical inversion VEMKZ data obtained in well entering terrigenous reservoir under-lied by thin layer with high resistivity have been processed. Starting model for inversion is generated by taking direct current data into account. Examples of real VEMKZ data interpretation are demonstrated. For investigations in deviated and horizontal wells the approach for finding true formation resistivity in thin reservoir using high-frequency induction measurements was proposed. This approach based on numerical signal modeling for deviated tool in horizontally-stratified earth. Algorithms for electrical anisotropy evaluating and thin-layer parameters estimating are observed.

The study focuses on processing methods for high-frequency induction data from deviated and horizontal wells. Simulation of electromagnetic fields with analytical algorithms is used to study how the resistivity of rocks above and below the well influences the acquired data. The simulations show that the contribution of under- and overlying layers into the recorded responses is considerable and depends on resistivity contrasts between the layers and on the position of logging arrays relative to the layer boundaries. This fact has to be taken into account when estimating true resistivity of reservoirs and when inverting induction logs from horizontal wells for reservoir characterization. The method is applied to oil- and water-saturated reservoirs in West Siberia, which contain high-resistivity impermeable layers leading to overestimation of apparent resistivity. Due regard for the effect of these layers in inversion of induction logs provides high-quality resistivity estimates.

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