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According to the authors, one of the important processes that have made their contribution to the formation of secondary porosity in the Bazhenov rocks are the epigenesis processes. Keeping in mind that these processes are related to the development of high reservoir properties of productive rocks, their importance for the prediction of promising areas where free oil may occur is significant. Unconventional reservoirs with mobile hydrocarbons are confined to weakened zones of the sedimentary mantle where oil generation is caused by conditioned heating related to certain hydrothermal-metasomatic processes in the basement rocks and structural features of the sedimentary mantle while boundaries of non-structural traps are defined by decompression zones. The exploration methods that can be used in a license block should be in accordance with the amount of geologic information available and determine target parameters for further more detailed and expensive explorations such as high-resolution 3D seismics and exploratory drilling.
The paper analyses the relevance of the obtained exploration results as well as the applicability of high-precision geophysical methods, such as detailed gravimetric and magnetic surveying and areal geochemical surveying, to identify unconventional and non-structural traps. The reason for integrating potential field data with seismic data is determined by the fact that information obtained by each of these methods has its specific characteristics. Anomalies of potential fields related to magnetic and density properties of rocks reflect, first of all, their composition and superimposed processes (tectonic impacts, hydrothermal-metasomatic changes, etc.) which allows obtaining data on physical characteristics of the geological environment in addition to seismic data that are crucial, mainly, to study structural features. Second, gravitational and magnetic fields anomalies are caused, primarily, by high-angle boundaries while the seismic method, in contrast, is focused on tracking low-angle boundaries. It means that these two methods may complement each other helping identify subvertical tectonic and subhorizontal lithological and stratigraphic boundaries.
