石油与天然气地质 ›› 2021, Vol. 42 ›› Issue (4): 931-948.doi: 10.11743/ogg20210414

• 油气地质 • 上一篇    下一篇

异常高有机质沉积富集过程与元素地球化学特征

邱振1(), 韦恒叶2,*(), 刘翰林1, 邵男3, 王玉满1, 张磊夫1, 张琴1   

  1. 1. 中国石油 勘探开发研究院, 北京 100083
    2. 西南石油大学 地球科学与技术学院, 四川 成都 610500
    3. 中国石油天然气集团有限公司 科技管理部, 北京 100007
  • 收稿日期:2021-04-27 出版日期:2021-08-28 发布日期:2021-08-27
  • 通讯作者: 韦恒叶 E-mail:qiuzhen316@163.com; qiuzhen@petrochina.com.cn;weihengye@163.com
  • 第一作者简介:邱振(1984-), 男, 博士、高级工程师, 非常规油气沉积学。E-mail: qiuzhen316@163.com; qiuzhen@petrochina.com.cn
  • 基金项目:
    国家自然科学基金项目(41602119);国家自然科学基金项目(41762003);中石油科技管理部课题项目(2021DJ2001);中石油勘探开发研究院院级项目

Accumulation of sediments with extraordinary high organic matter content: Insight gained through geochemical characterization of indicative elements

Zhen Qiu1(), Hengye Wei2,*(), Hanlin Liu1, Nan Shao3, Yuman Wang1, Leifu Zhang1, Qin Zhang1   

  1. 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
    2. School of Earth Science and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China
    3. Science and Technology Management Department, CNPC, Beijing 100007, China
  • Received:2021-04-27 Online:2021-08-28 Published:2021-08-27
  • Contact: Hengye Wei E-mail:qiuzhen316@163.com; qiuzhen@petrochina.com.cn;weihengye@163.com

摘要:

非常规油气甜点段形成与有机质沉积富集过程密切相关,特别是页岩油气,它们所赋存或与之紧密联系的细粒沉积岩中总有机碳含量(TOC)一般大于3.0%。提出TOC含量≥3.0%的细粒沉积(物)岩称为异常高有机质沉积,以及异常高有机质沉积富集的概念性假设,并指出高的初级生产力水平是其形成的前提和决定性因素,缺氧的水体环境更易形成大规模异常高有机质沉积。基于对有机质沉积聚集过程相关元素的生物地球化学循环特征解剖,以四川盆地五峰组-龙马溪组为例,深入探讨高精度元素地球化学数据约束条件下的异常高有机质沉积富集过程,证实了异常高有机质沉积富集的概念性假设,并得出它们的形成是水体表层高的初级生产力及其与水体循环共同控制着的氧化还原条件这两大因素动态演化的结果。异常高有机质沉积富集过程的研究有助于深化对页岩油气甜点段形成机理的认识,是非常规油气沉积学的重要研究内容之一,可为非常规油气资源勘探开发提供重要理论支撑。

关键词: 异常高含量有机质, 细粒沉积(物)岩, 页岩油气, 非常规油气沉积学, 龙马溪组, 四川盆地

Abstract:

Organic matter (OM) accumulation plays a key role in the development of sweet spots in unconventional oil and gas plays, especially in shale. Fine-grained sedimentary rocks containing or associated with sweet spots generally have TOC content of higher than 3.0%. We define these sediments or sedimentary rocks with TOC ≥ 3.0% as the extraordinary high organic matter (EHOM) deposits, and propose conceptual hypotheses for the accumulation process of EHOM. We suggest that high primary productivity provides prerequisites for OM accumulation and that the anoxia is prone to enhance large scale accumulation of EHOM. We use the Wufeng-Longmaxi formations in the Sichuan Basin to carry out a case study for the discussion on the elemental bio-geochemical cycles during the EHOM accumulation processes. The conceptual hypothesis for EHOM enrichments constrained by elementary geochemistry is verified. Our result shows that the EHOM enrichment in the Wufeng-Longmaxi formations was the results of dynamic evolutions of the high primary productivity and the redox conditions jointly controlled by high primary productivity and water circulation. As one of the research targets of unconventional petroleum sedimentology, this study could help better understanding the forming mechanism of the "sweet-spots" and further support unconventional petroleum exploration and development.

Key words: extraordinary high organic matter content, fine-grained deposits, shale oil and gas, unconventional petroleum sedimentology, Longmaxi Formation, Sichuan Basin

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