Acta Scientiarum Naturalium Universitatis Pekinensis

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Biogenic Silica of Organic-Rich Shale in Sichuan Basin and Its Significance for Shale Gas

WANG Shufang1,2, ZOU Caineng2, DONG Dazhong2, WANG Yuman2, HUANG Jinliang2, GUO Zhaojie1   

  1. 1. The Key Laboratory of Orogenic Belts and Crustal Evolution MOE, School of Earth and Space Sciences, Peking University, Beijing 100871; 2. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083;
  • Received:2013-04-06 Online:2014-05-20 Published:2014-05-20



  1. 1. 造山带与地壳演化教育部重点实验室, 北京大学地球与空间科学学院, 北京100871; 2. 中国石油勘探开发研究院, 北京 100083;

Abstract: Through analysis of shale petrology, TOC, major elements and physical mechanism, this paper studies on silicon genesis of upper Odorvision Wufeng Formation and lower Silurian Longmaxi Formation in Changning- Shuanghe profile of Sichuan Basin. The results indicate that up to 40%?62.7% SiO2 in lower part of the profile is excess. They are characterized by high SiO2, P2O5, Fe2O3 and low Al2O3, TiO2, FeO, MgO content. Al/(Fe+Al+Mn) varies between 0.67?0.71, and Si/(Si+Al+Fe) between 0.89?0.93. In Al-Fe-Mn diagram, they are in biogenic area. TOC of Wufeng Formation is 2%?7.55%, average 3.73% and 0.23%?8.36%, average 1.16% for Longmaxi Formation. Segment of TOC > 2% mainly concentrated in the lower part, with thickness of 21 m. TOC and siliceous content have good positive correlation. Under the microscope, there are a lot of microfossils, such as radiolarians, sponge spicules, indicating the biogenic silica. Biogenic silica indicates sedimentary environment of deep shelf and is conducive to the formation of natural fractures and fracturing treatment, which is of great significance for shale gas exploration and development.

Key words: Sichuan Basin, organic-rich shale, biogenic silica, fracture

摘要: 通过岩石学、有机碳含量、主量元素和力学性质分析, 对四川盆地长宁双河剖面上奥陶统五峰组和下志留统龙马溪组页岩进行硅质成因研究。长宁双河剖面底部页岩过量硅含量为40%~62.7%, 具有高SiO2, P2O5和Fe2O3, 低Al2O3, TiO2, FeO和MgO的特征。Al/(Fe+Al+Mn)比值为0.67~0.71, Si/(Si+Al+Fe)比值为0.89~0.93, 在Al?Fe?Mn图解上落在生物成因区。五峰组有机碳含量(TOC)为2%~7.55%, 平均3.73%。龙马溪组页岩有机碳含量为0.23%~8.36%, 平均1.16%, TOC>2%段集中在剖面底部21 m, TOC与硅质含量具有正相关关系。页岩中发现大量放射虫、海绵骨针等微体化石, 证实硅质为生物成因, 指示页岩沉积环境为深水陆棚, 有利于形成自然裂缝和后期压裂改造, 对页岩气勘探开发具有重要意义。

关键词: 四川盆地, 富有机质页岩, 硅质生物成因, 裂缝

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