Sequence stratigraphic framework and sedimentary facies prediction in Dongying Formation of Nanpu Sag

The Nanpu Sag is a downfaulted lacustrine basin with strike-slip faulting.The Palaeogene Dongying Formation is dominated by the depositional system of alluvial fan facies,fan delta facies(braided delta facies) and lacustrine facies.With the high resolution sequence stratigraphy and the correlation analysis of cores,logs and seismic data,different orders of sequence boundaries and facies sequence are identified and the isochronous stratigraphic framework and the depositional evolutional model of Dongying Formation are built and used to predict the distribution of reservoirs.The study shows that stratigraphic sequence boundary,maximum flood surface,sedimentary facies and structural settings are the dominant factors controlling the distribution of favorable sand bodies and oil reservoirs in the Dongying Formation.The distribution of oil reservoirs is dominated by such characteristics as relatively vertical concentration and area zonation.A lot of hydrocarbon reservoirs are concentrated in Ed_1 that underlies the maximum flood surface vertically.Those discovered reservoirs are typically distributed in the second strike-slip fault zone in Nanpu Sag.