Sedimentary System Research In Chengbei In Palaeogene

Chengbei Zone is located in the southeast of Huanghua Depression of Bohai Bay Basin, in the neighborhood of Chengning Uplift. It is a special gentle slope caused by the fault. The research on the characteristics of sedimentary in gentle slope is rare. Dongying Formation which deposit in dormant rift of continental rift basin is different from the Shahejie Formation which deposit intense, constant rift of continental rift basin. Because of the reasons, the paper chooses Dongying Formation in Chengbei Zone to study. Guided by the theory of continental sequence stratigraphy, The aim was to reveal the sequence characteristics and its gentle slope depositional system evolution characteristics in Dongying Formation.Through the analyses of drilling core face, well log face and seismic face, the paper identifies 3 types of sedimentary system, namely delta sedimentary system, lake sedimentary system and gravity current sedimentary system.Based on the datas of drilling core, abundant 3-Dseismicdata, core data and logging data, utilizating the method of continental sequence stratigraphy, according to the characteristics of different levels of sequence boundaries, the paper divides Dongying Formation into 6 third-order sequences and 15 system tracts,On the basis of constitution of region sequence stratigraphic framework, referring to the analysis of paleo-provenances, the percent of sandstone, seismic face and seismic information, the paper analyses the distribution and evolution of sedimentary system of each sequence.constitutes the mode of sedimentary system of the gentle slope of Chengbei zone in Dongying Formation. It is a combination of meandering river delta sedimentary system lake-gravity sedimentary system and current sedimentary system. Through the sequence stratigraphy correlation, the following conclusions are drawn: Sequence boundaries are clear and sequences distribute discontinuously, there are no SQ1 or SQ6 on the top of the gentle slope, and all sequences distribute in the inner of the depression. In the sequence lowstand systems tract(LST) rarely occurs expanding systems tract(EST)Lack sands, while highstand systems tract (HST) develops thick sands, highstand systems tract (HST) is the main department of the sequence. The constitution of the mode will guide the exploration of the petroleum and gas of the zone.