[en] The technique of the determination of residual oil-saturation coefficient of inundated interbeds using pulsed neutron-neutron logging (PNNL) is described. The time PNNL-aided measurements were carried out when boring prospecting boreholes at the Tuymasinskoe oil deposit for the determination of the oil saturation coefficient. Results of the determination of the residual oil saturation coefficient of inundated strata are discussed using prospecting borehole investigation data. Time measurements by the PNNL method permit to evaluate qualitatively the extent to which the stratum is being exploited and together with other geophysical logging techniques permit to determine the value fo the current oil output from inundated interbeds under the assumption that oil saturation, residual oil saturation and current saturation coefficients are specified. A drawback of this technique is that time periods between measurements are rather long. The method may have an extensive application for the regular control of development of deposits