Lixian Slope Shahejie Formation Sequence Stratigraphy Study

The Shahejie Formation is the major exploration target of Lixian Slope. As exploration becomes more and more difficult, the exploratory objects transfer gradually from the structure reservoirs which are easy to be distinguished to subtle reservoirs, such as lithologic or stratigraphic reservoirs. So, more accurate research results of sedimentary facies and sandbody distribution are needed urgently. The key target of sequence stratigraphy is just to construct isochronous lithologic framework for the study on facies and depositional systems, then to predict the reservoir distribution and reservoir-cap rock assemblage more efficiently.Using plentiful geological and geophysical data, and based on the fundamental principles of sequence stratigraphy, the isochronal framework of sequence stratigraphy was established. Based on the identification of facies markers in core, log, seismic and palaeontologic, the depositional system distribution in isochronal frame of sequence stratigraphy were discussed.Based on the boundary marks of sequence stratigraphies at all levels, all the sequences and their boundaries of the Shahejie Formation were delineated. The Palaeogene Formation can be subdivided into three2nd-order sequences with ten3rd-order sequences. The Kongdian Formation and the forth members of the Shahejie Formation is the first of the2nd-order sequences.The third members of the Shahejie Formation and the second members of the Shahejie Formation is the second of the2nd-order sequences. The first members of the Shahejie Formation and Dongying Formation is the third of the2nd-order sequences.The ten3rd-order sequences is the Kongdian Formation (SQ1), the forth members of the Shahejie Formation (SQ2), the lower member of Es3(SQ3), the middle member of Es3(SQ4), the upper member of Es3(SQ5), the second members of the Shahejie Formation (SQ6), the first members of the Shahejie Formation (SQ7), the third members of the Dongying Formation (SQ8), the second members of the Dongying Formation (SQ9) and the first members of the Dongying Formation (SQ10).Through sequence stratigraphic subdivision and correlation of key wells and seismic sections, the sequence stratigraphic framework was established.On the base of the sedimentary facies analysis of single well and combining with the characteristics of logging curves and the testing results, braided river delta, lacustrine and braided river are identified in the isochronal framework of sequence stratigraphy of SQ5-SQ7. By studying depositional system in isochronal frame of sequence stratigraphy, the distribution rules of sedimentary facies were studied in detail. The SQ5is the braided delta front and coastal lake deposition system. The early of SQ6is braided delta plane, braided delta front and coastal lake deposition system. The late of SQ6is braided river deposition system. The early of SQ7is the shallow lake and semi-deep lake deposition system. It have a lot of the sandy shore-bar and carbonate shore-bar deposition. The late of SQ7is braided delta plane and braided delta front deposition system.