Emsian-Lower Frasnian play of Blagoveschensky depression: paleogeographic patterns of formation and types of non-anticlinal traps

For successful prospecting for new accumulations in the Devonian series, it is necessary to refocus investigations on the detailed lithological and paleogeographic patterns of reservoir rock occurrence. Prospecting for new lithological objects was carried out on the basis of integrated studies including sedimentological analysis of core and well logs, geological interpretation of close-spaced 2D CDP and 2DW CDP seismic survey lines. The developed geoseismic criteria of deposit genetic type identification allowed delineating and tracing seismic images (seismic facies) of channel (deltaic or delta-front), beach-bar types of deposits in seismic sections, as well as small biohermal buildups and their clastic aprons the prospecting for new objects is associated with. A series of detailed lithological and paleogeographic maps showing zones of different types of terrigenous and carbonate deposit occurrence are prepared for each horizon. The revealed lithofacies and paleogeographic zoning correlate with the reservoir occurrence patterns. Sandy-siltstone reservoirs confined to the arms of subaerial and subaqueous delta parts are favourable for formation of stratigraphic and lithologically screened traps. Accumulations of structural type limited by facies changes are more likely predicted in the zones of delta fans with blanket form of reservoir distribution. Small buildups and their aprons are promising for the prospecting of stratigraphic and lithologically screened traps. Siltstone-argillaceous, argillaceous, and carbonate deposits of shallow marine shelf and still-water interchannel bars form seals and lateral impermeables. The work conducted allowed identifying new prospecting objects and recommending further studies of non-anticlinal traps most morphologically expressed and substantiated by seismic data