Oil & Gas Geology ›› 2015, Vol. 36 ›› Issue (4): 612-620.doi: 10.11743/ogg20150411

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Sedimentary characteristics of gravelly beach-bar in the Lower Cretaceous Tenggeer Formation of Baiyinchagan sag, Erlian Basin

Gao Hongcan1, Xiao Bin2, Zheng Rongcai3, Liu Yun2, Tan Xianfeng1, Shang Yazhen4, Zhang Bin5   

  1. 1. School of Petroleum Engineering, Chongqing University of Science & Technology, Chongqing 410331, China;
    2. Geophysical Research Institute of Zhongyuan Oilfield Company, SINOPEC, Puyang, Henan 457001, China;
    3. State Key Laboratory of Oil and Gas Reservoir Geology and Exploration, Chengdu University of Technology, Chengdu, Sichuan 610059, China;
    4. Research Institute of Exploration and Development, Zhongyuan Oilfield Company, SINOPEC, Puyang, Henan 457001, China;
    5. No.2 Drilling Company, Zhongyuan Petroleum Engineering Co.Ltd., SINOPEC, Puyang, Henan 457001, China
  • Received:2014-08-26 Revised:2015-05-20 Online:2015-08-08 Published:2015-08-28

Abstract:

In order to demonstrate the sedimentary characteristics of gravelly beach-bar in the Lower Cretaceous Tenggeer Formation in the joint area of the Xilinhaolai and Daerqi of the southern gentle slope of the Baiyinchagan sag, Erlian Basin, abundant cores and logging data were utilized to analyze the spatial distribution, texture, sedimentary structure and vertical sedimentary sequences in the context of regional geological setting.The beach-bar conglomerates occur in the debris flow conglomerates and pebble sandstone-mudstone as thin interbeds, featuring in fair roundness but worse sorting, relative abundance of pebbles with barred and flat shape, and Janus configuration of maximum flat plain/major axis.It is in gradational contact with the underlying debris-flow deposits featuring in reverse grading, while it is in abrupt contact with the overlying shallow lake mudstones or debris-flow deposits, featuring, as a whole, in vertical alternation of reverse and normal grading.The sedimentary model in the study area is dominated by elutriation and winnowing of the early debris-flow deposits by the waves in the waterfront and shallow lacustrine.The fine-grained clasts were transported to the shallow lake to form the sandy beach-bar, while the pebbles stayed to form gravelly beach-bar, with troughs possibly occurring between these two deposits system.They were formed under 4 main conditions, namely the powerful water strength, low relief landform, low system tract(LST)and suitable sedimentary sources.

Key words: gravelly beach-bar, Tenggeer Formation, Lower Cretaceous, Baiyinchagan sag, Erlian Basin

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