中、上扬子龙马溪组层序划分及对页岩储层发育的控制
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本文为中国石油天然气集团公司重大现场试验项目(编号2019F- 31)资助的成果。


Sequence division of the Longmaxi Formation and their control on shale reservoir development in Middle- Upper Yangtze
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    摘要:

    以详细的岩相研究为基础,利用岩相的垂向叠置关系,结合测井、有机地球化学、沉积特征、矿物学特征、元素地球化学等分析,将中、上扬子下志留统龙马溪组划分为2个具有完整海侵和海退的三级层序,即SQ1~SQ2,平均延时约为2. 5Ma。龙马溪组页岩储层主要发育7种成因类型的微米—纳米级微观储集空间,裂缝储集空间为构造剪裂缝和页理缝2类。通过不同孔径孔隙体积与有机碳含量的关系以及页岩对甲烷吸附能力分析,页岩储层孔隙发育主要受有机碳含量控制。富有机质页岩发育受控于有机质生产力、有机质聚集及有机质保存,最大海泛面附近的δ13Corg介于-31‰~-30‰之间,高活性铁含量介于1. 0%~1. 56%之间,δ13Corg负漂移及高活性铁含量最大,指示了最高的古生产力;沉积速率在最大海泛面附近约为7. 5m/Ma,较低的沉积速率有利于有机碳聚集,其有机碳含量高达2%~6%;最大海泛面附近Th/U比值一般为0. 24~0. 54,V/Cr比值为5. 26~8. 27,表现出强缺氧还原环境,有利于有机质保存。因此,最大海泛面附近为富有机质页岩发育段,是寻找页岩气有利层段。

    Abstract:

    On the basis of detailed lithofacies study, the Longmaxi Formation of Lower Silurian in the MiddleUpper Yangtze is divided into two thirdorder sequences with complete transgression and regression, namely SQ1SQ2, with an average delay of 2.5 Ma. There are mainly seven types of micronano scale microscopic space in the Longmaxi Formation shale reservoir, and fracture reservoir space includes structural shear fracture and foliation fracture. The analysis of relationship between pore volume of different pore size and organic carbon content and methane adsorption capacity of shale indicates that the pore development of shale reservoir was mainly controlled by its organic carbon content. The development of organic rich shales was controlled by organic matter productivity, its accumulation and preservation. The δ13C org near the most flooded surface ranges from -31‰~-30‰, and the content of highly active iron ranges from 1. 0%~1. 56%. The negative drift of δ13 C org and the content of highly active iron are the largest, indicating highest paleoproductivity. The deposition rate is about 7. 5 m/Ma near the most flooded surface. The lower deposition rate is favorable for the accumulation of organic carbon, and the content of organic carbon is as high as 2%~6% in shale.The Th/U ratio is generally 0. 24~0. 54, and V/Cr ratio is 5. 26~8. 27 near the most flooded surface indicating a strong anoxic reducing environment that is conducive to the preservation of organic matter. Therefore, the section of organic rich shale near the most flooded surfaceis favorable for shale gas exploration.

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熊绍云,王鹏万,黄羚,邹辰,贺训云,李昌,徐政语.2020.中、上扬子龙马溪组层序划分及对页岩储层发育的控制[J].地质学报,94(11):3471-3487.
XIONG Shaoyun, WANG Pengwan, HUANG Ling, ZOU Chen, HE Xunyun, LI Chang, XU Zhenyu.2020. Sequence division of the Longmaxi Formation and their control on shale reservoir development in Middle- Upper Yangtze[J]. Acta Geologica Sinica,94(11):3471-3487.

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  • 收稿日期:2019-07-04
  • 最后修改日期:2020-08-31
  • 录用日期:2020-10-06
  • 在线发布日期: 2020-10-10
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