Oil & Gas Geology ›› 2017, Vol. 38 ›› Issue (2): 259-269.doi: 10.11743/ogg20170206

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Sedimentary filling evolution of small-scale lake basins during intensive faulting:an example from the Shahezi Formation of Songzhan region in Xujiaweizi fault depression,Songliao Basin

Cai Quansheng1,2, Hu Mingyi1,2, Hu Zhonggui2, Deng Meng4   

  1. 1. Key Laboratory of Oil and Gas Resources and Exploration Technology, Ministry of Education, Yangtze University, Wuhan, Hubei 430100, China;
    2. School of Geosciences, Yangtze University, Wuhan, Hubei 430100, China;
    3. Hubei Cooperative Innovation Center of Unconventional Oil and Gas, Wuhan, Hubei 430100, China;
    4. Exploration and Development Research Institute, Tianjin Branch of CNOOC Limited, Tianjin 300452, China
  • Received:2016-09-15 Revised:2017-02-15 Online:2017-04-28 Published:2017-05-04

Abstract: The Songzhan region in northern Xujiaweizi Fault Depression of Songliao Basin is a small-scale faulted basin.The latest drilling data shows great gas potential in the basin and a possible replacement of the depleting deep gas zones in Daqing Oilfield.We chose the Shahezi Formation in the basin as a research object to analyze the stratigraphic sequences,sedimentary systems and filling-up history of small scale lake basins during intensive faulting based on previous studies as well as data of core,mud logging,conventional logging and 3D seismic survey.The result shows that the Shahezi Formation can be divided into one second-order sequence and four third-order sequences,with the latter being further subdivided into LST,TST and HST,according to lake flooding surfaces.Four kinds of sedimentary facies,including braided delta,fan delta,lacustrine and volcaniclastic facies,were recognized.The filling-up history of the Formation appears to be quite different from that of large-scale fault basins.Fan deltas dominated both steep and gentle slopes at the early stage of intensive faulting.And zonation of sedimentary facies was only distinctive with the expansion of the basin.How-ever,they were segmented into many shore-shallow lacustrine sedimentary zones with multiple depocenters due to a sediment supply shortage in the short axis of the basin.As a result,the thickness of layers in the basin varies greatly from one area to another.We proposed in the paper a sedimentary model for the continental narrow faulted lake basins based on the study of the filling-up history of the Shahezi Formation.

Key words: sedimentary facies, sequence stratigraphy, sedimentary model, Shahezi Formation, Xujiaweizi Fault Depression, Songliao Basin

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