Outcrop-Based Analysis of a DeepWater Gravity Flow Sediments in Lake: A Case Study from the Chang 7 of Yaoqu Section, Ordos Basin
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Laboratory of Exploration Technologies for Oil and Gas Resources (Yangtze University), Ministry of Education,Wuhan, 430100, China

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    Abstract:

    Outcrop based sedimentary section plays an irreplaceable role in detailed anatomy for internal architecture of sedimentary bodies and building accurate geological model of underground. Taking the Chang 7 of Yaoqu Section developed in the south of Ordos Basin as an example, the type, characteristics, vertical sequence and sedimentary environment of deep-water gravity flow deposits of deep-water lithofacies were anatomized, employing the research thought of geology, field outcrops and sedimentology. According to this study, 5 lithotypesincluding massive fine silt facies, Bouma Sequence siltstone facies, horizontal lamination bedding mudstone facies, massive mudstone facies and tuff facies, 5 kinds of sedimentary elements including debris flow deposit, turbidite deposit, slump deposit, deep-water original deposit and tephra deposit. 5 kinds of sedimentary element constitue the vertical distribution form of A,B,C,D in vertical direction. On this basis, in combination with the regional geological features, it suggested that the sedimentary system developed in Chang 7 mainly include lake and channel gravity flow deposit. Lacustrine facies could further determine the shore-shallow lake facies, deep-water in situ sedimentary micro facies, the most developed lithofacies association is class D. Channel gravity flow deposit could be furtherly divided into 4 subphases such as near source channel, far source channel, embankment and front lobe bodies, 3 micro phases such as sandy bebris flow deposit, turbidite deposit and slump deposit are also included. Near source channel embankment formed class A, class C and class B lithofacies associations, far source channel embankment formed class B and class C lithofacies associations, front lobe developed class C lithofacies association. The profile phase analysis showed that the top quality hydrocarbon rock and gravity flow sandbody in study area could form better “lower-generation and upper storage” tight lithology oil and gas reservoir.

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LV Qiqi, LUO Shunshe, FU Jinhua, XIANG Ji, NIU Xiaobing, GONG Chen, XU Liming, FENG Shengbin, LI Shixiang.2017. Outcrop-Based Analysis of a DeepWater Gravity Flow Sediments in Lake: A Case Study from the Chang 7 of Yaoqu Section, Ordos Basin[J]. Acta Geologica Sinica,91(3):617-628

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History
  • Received:May 07,2015
  • Revised:January 03,2016
  • Adopted:January 28,2016
  • Online: March 16,2017
  • Published: