Prediction of Thin-Layer Thickness Using Seismic Full-Waveform Modeling

The aim of this work was to select a method for studying the quantitative characteristics of the reservoir properties of the Pre-Jurassic oil and gas complex of Western Siberia by 3D seismic data and to test it on real data. The weathering crust in the Pre-Jurassic complex of Western Siberia is chosen as a methodological example, since reflections from its top and bottom do not differ due to its relatively small thickness (from 0 to 50 meters). The amplitude-frequency response of this interference reflection depends on the thickness, therefore, some seismic attributes may react to it. Full-waveform seismic modeling, using the spectral element method (SEM), was performed for the first time to clarify these relations within the framework of the advanced domestic CAE FIDESYS software developed by graduates and the staff of the Chair of Computational Mechanics of Moscow State University and adapted by the staff and graduate students of the Geology Department of Moscow State University to solve these tasks. This article presents the first results of its practical use. The comparative calculations show that the traditional ray-trace modeling methods previously used in seismology in combination with convolving with reflection coefficients give false results and therefore are not recommended for further use. The proposed and tested technology enables us to construct a forecast map of the thickness of the potentially oil- and gas-bearing weathering crust in the top of the Pre-Jurassic complex in the area of the 3D survey.