The article presents the results of experimental studies of geologic profile over hydrocarbon deposits in the Republic of Belarus. Experimental studies were carried out at the Marmovichi and the Geologicheskoye fields of hydrocarbon deposits in the Gomel region. Measurement of the phase of the surface impedance of the geological profile over hydrocarbon deposits under the influence of electromagnetic waves with amplitude-frequency modulation was carried out. It has been found that the use of two modes for measuring the phase of surface impedance increases the accuracy of delineation of hydrocarbon deposits. A method at carrier frequencies of 0.1...2 GHz for amplitude-frequency modulated signals has been developed. The above studies can be applied to the development of methods for exploration of hydrocarbon deposits.