Интерпретация данных зондирования методом становления поля в ближней зоне с учетом индукционно-вызванной поляризации при площадных нефтегазопоисковых исследованиях на юге Сибирской платформы

The main electrical prospecting technique in the study of the geological section of the Siberian platform sedimentary cover is a near-field transient electromagnetic method (TEM) used for oil and gas exploration along with seismic prospecting. In recent years more and more signals complicated by the effect of induction-induced polarization (IIP) are registered. Interpretation of such signals in the horizontally stratified conductive models leads to errors when defining the resistivity of the sedimentary cover horizons located in the target interval of the section. The aim of the study has been to define the IIP-complicated transient response registered during the areal exploration for oil and gas, as well as to develop guidelines for interpreting the TEM data with the account of the induced polarization (IP). Using mathematical modeling, the IP effect has been evaluated for the transient characteristics calculated by the model in which the polarized horizon is located at different depths. Based on the TEM data inversion results considering the IP, the effectiveness of methodology has been validated. According to the inversion results, the IP manifestation is associated with the rocks in the upper part of the section. The nature of IP is explained by the presence of pyrite in the Jurassic and Upper Cambrian sediments. The resistivity distribution for the target horizons with the account of IP is lognormal. Applying the parameter characterizing the TEM curve divergence at the qualitative analysis stage allows the area zoning by the degree of IIP manifestation. Interpretation of the TEM data with the account of IP enhances the accuracy of the TEM data inversion and allows to obtain the models that are consistent with the geological structure of the survey area. Thus, it enables a detailed forecast of the reservoir properties of the subsalt sediments