Oil & Gas Geology ›› 2018, Vol. 39 ›› Issue (6): 1280-1292.doi: 10.11743/ogg20180617

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Analysis of the “Source-to-Sink” system in the 2nd member of the Paleogene Dongying Formation in the eastern slope of Chengdao in Bozhong Say,Bohai Bay Basin

YangKe1,2, DongYanlei1,2, Zhu Xiaomin1,2, Pan Rong1,2, Zhang Mengyu1,2, Wu Wei1,2, Wang Heng1,2   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China;
    2. College of Geosciences, China University of Petroleum(Beijing), Beijing 102249, China
  • Received:2018-06-13 Revised:2018-08-20 Online:2018-12-28 Published:2018-10-22

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Abstract: “Source-to-Sink” system is a hot topic in recent sedimentology research.The eastern slope of Chengdao,which constitutes a complete “Source-to-Sink” system together with Chengbei low salient and its surrounding depositional areas,is a transitional slope zone from Chengbei low salient to Shanan and Bozhong Sags,and located in Bohai Bay Basin.Based on the core,logging and 3D seismic data,we defined the basement rock types of provenance,reconstructed the palaeogeomorphology of the 2nd member of Dongying Formation(Dong 2 member),made a quantitative analysis of elements in the “Source-to-Sink” system,finely mapped the sand bodies within the depositional area,and established the coupling model of the “Source-to-Sink” system in the eastern slope of Chengdao.The results show that the isolated flood sublacustrine fan deposits,being predominant in the Dong 2 member,are all sourced from Chengbei low salient,and their basement rocks are composed mainly of clastic and pyroclastic rocks.The distribution patterns and scales of sand bodies in depositional areas are mainly controlled by source type,relief,area of catchment,size of transportation pathways,slope break zone,palaeomorphology of depositional area and so on.Among them,the total volume of sediments imputing into the depositional area is closely related to the relief and the catchment area.The larger the relief(averaging at about 1 280 m)and catchment area(averaging at around 7 km2)are,the larger the scale of the fan system will be;on the contrary,the fan system contracts accordingly.In addition,the palaeogeomorphology in the depositional area and slope break zone also exert an important control on the size of fan system.Two types of slope break zones were recognized in this study,namely the topographic and fault slope break zones.The angles of the slope break zones range between 3.9° and 9.8°,and show a positive correlation with both the fan body thickness and area.Meanwhile,the size of transportation channels(width/depth ratio and cross-sectional area)also determines the distribution characteristics of sand bodies.In summary,the elements in the “Source-to-Sink” system in the study area are relatively stable during the deposition of the study interval.Finally,we proposed a multi-factor coupling model of source areas with multiple lithologies(provenances)-channels of paleo-ravines or fault troughs within provenance-transportation pathways of topographic/fault slope break zones(transportational area)- isolated flood sublacustrine fan(sinks).This model establishes the relationship between the size of sand bodies and their provenances,and provides potential implications for predicting favorable sand bodies in future oil and gas exploration.

Key words: “Source-to-Sink” system, Dongying Formation, eastern slope of Chengdao, Jiyang Depression, Bohai Bay Basin

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