Oil & Gas Geology ›› 2012, Vol. 33 ›› Issue (3): 432-441.doi: 10.11743/ogg20120313

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Characteristics of Silurian Paleo-oil reservoirs and their significance for petroleum exploration on the southeast margin of Sichuan Basin

Ma Wenxin1, Liu Shugen1, Huang Wenming2, Zhang Changjun1, Xu Guosheng1, Yuan Haifeng1   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China;
    2. Research Institute of Exploration and Development, CNPC Chuanqing Drilling Engeering Company Limited, Chengdu, Sichuan 610051, China
  • Received:2011-12-02 Revised:2012-05-10 Online:2012-06-28 Published:2012-07-10

Abstract:

In order to understand the hydrocarbon accumulation characteristics of the Silurian carbonates on the southeast margin of Sichuan Basin,this paper studied reef-shoal facies sedimentary features and paleo-oil reservoirs in the Lower Silurian Shiniulan Formation based on the comprehensive field and laboratory research of petrography and geochemical analysis.The Lower Silurian Shiniulan Formation is composed of upward-shallowing three cyclic deposits,of which the third cyclic deposits are bioherm-shoal facies on platform margin occurring along Lintanchang-Liangcun-Dingshan structures.The reservoirs of reef-shoal facies are rich in bitumen,indicating that they are lithologic paleo-oil reservoirs of shoal-reef type.These paleo-oil reservoirs are small in resource scale and scatter in regional distribution.Their resources are estimated to be about 6.62?103 t.The oil of the paleo-oil reservoir is mainly sourced from the Sinian paleo-oil reservoir,partly from the Silurian source rocks.The formation and destruction of the Shiniulan paleo-oil reservoir includes the following process:the Sinian oil reservoirs were destroyed and the escaping oil accumulated in the Shiniulan Formation to form the oil reservoir(Late Triassic to Early Jurassic).The oil of the oil reservoir was cracked to gas due to the long term deep burial,to lead to the gas reservoir(Middle Jurassic to Middle Cretaceous).Finally,the gas reservoir was destroyed by folding and quick uplifting(since 80 Ma).The exploration prospect in the Silurian in southeast Sichuan Basin is not as good as in the eastern Sichuan-eastern Chongqing.

Key words: reef-shoal facies, Silurian, geochemistry, paleo-oil reservoir, Sichuan Basin

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