Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (1): 50-66.doi: 10.11743/ogg20190106

• Petroleum Geology • Previous Articles     Next Articles

Petrologic characteristics and genesis analysis of the Ordovician Wufeng Formation-Silurian Longmaxi Formation in Laifeng-Xianfeng area of western Hubei

Wang Xiuping1,2, Mou Chuanlong1,2, Xiao Zhaohui3, Chen Yao3, Wang Qiyu1,2   

  1. 1. Key Laboratory Sedimentary Basins Oil and Gas Resources, Ministry of Land and Resources, Chengdu, Sichuan 610081, China;
    2. Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu, Sichuan 610081, China;
    3. Hubei Shale Gas Development Co., Ltd., Wuhan, Hubei 430060, China
  • Received:2018-01-03 Revised:2018-10-19 Online:2019-02-28 Published:2018-12-08

Abstract:

As part of western Hubei province,Laifeng-Xianfeng area is adjacent to the east of Sichuan Basin,with its Upper Ordovician Wufeng-Lower Silurian Longmaxi Formation dark rock series bearing lower organic abundance.The petrological and mineralogical characteristics of Upper Ordovician Wufeng-Lower Silurian Longmaxi Formations in Laifeng-Xianfeng area, were investigated according to detailed observation of the six outcrop sections and three cores, in combination with polarizing microscope,X-ray diffraction(XRD),field emission scanning electron microscopy(SEM)and organic carbon content(TOC)analysis.Large amount of clastic particles in silt size are developed in the study area whose mineral components are mainly quartz and clay minerals.Besides,siltstones and shales rich in organic matters are the main rock types in this area,which can be divided into four lithologic sections from the bottom-up including carbonaceous and siltyshales,carbonaceous and argillaceous siltstones,argillaceous siltstones and carbonaceous siltyshales.According to instructionsby petrological and mineralogical characteristics and geochemistry of element,and comparison of shale enrichment conditions with the corresponding formation of Sichuan Basin,it can be figured out that the shorter-term anoxic and reducing environment,rapid change of sea level and smaller rate of deposition,render the thickness and abundance of organic matters of organic-rich shales in the Wufeng-Longmaxi Formations in Laifeng-Xianfeng area with higher bioproductivity to be significantly worse than those of the corresponding formation in Sichuan Basin.

Key words: mineral component, rock type, Wufeng-Longmaxi Formations, Laifeng-Xianfeng area, Sichuan Basin, Middle Yangtze region

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