西南石油大学学报(自然科学版)

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Study on Longmaxi Formation Bottom Boundary in Sichuan Basin

Wang Xingzhi1, Li Yizhen1, Du Yang1,2, Hu Yang2, Li Ye1   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploration,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    2. Geological Exploration & Development Institute,Chuanqing Drilling Engineering Co. Ltd.,CNPC,Chengdu,Sichuan 610052,China
  • Online:2014-02-01 Published:2014-02-01

Abstract:

In order to solve the partitioning problem on the bottom boundary of lower Silurian Longmaxi Formation,based
on previous researches,with the macroscopic and microscopic observation of outcrops and drilling cores and the analysis of
well logging,mineralogical and geochemical data in Sichuan Basin and its peripheral areas,the differences between Longmaxi
and Wufeng Formation show that there are higher limy content,many brachiopods,low GR and high RT logging values,high
calcite content and lower TOC values in the top of Wufeng Formation,while the bottom of Longmaxi Formation have none
limy content,none brachiopods and abundant graptolites,high GR and low RT logging values,high clay and quartz content,
highest TOC values. The study suggested that the detection of limy content and comparison of log are the fast and accurate
methods of demarcating Longmaxi Formation bottom boundary in practical operation,and it can provide some theoretical basis
for furthermore shale gas exploration in Longmaxi Formation of Sichuan Basin.

Key words: Sichuan Basin, Longmaxi Formation, bottom boundary, Wufeng Formation, lower Silurian