石油学报 ›› 2019, Vol. 40 ›› Issue (s1): 153-165.DOI: 10.7623/syxb2019S1013

• 地质勘探 • 上一篇    下一篇

珠江口盆地东部始新世-渐新世沉积环境演变及对烃源条件的影响

张丽丽, 舒誉, 蔡国富, 龙祖烈, 刘冬青, 王菲   

  1. 中海石油(中国)有限公司深圳分公司研究院 广东深圳 518067
  • 收稿日期:2018-07-10 修回日期:2018-11-23 出版日期:2019-07-25 发布日期:2019-07-15
  • 通讯作者: 张丽丽,女,1978年10月生,2002年获中国地质大学(武汉)学士学位,2008年获中国科学院南海海洋研究所博士学位,现为中海石油(中国)有限公司深圳分公司研究院工程师,主要从事地层对比及油气地质等方面的研究。Email:zhanglili@cnooc.com.cn
  • 作者简介:张丽丽,女,1978年10月生,2002年获中国地质大学(武汉)学士学位,2008年获中国科学院南海海洋研究所博士学位,现为中海石油(中国)有限公司深圳分公司研究院工程师,主要从事地层对比及油气地质等方面的研究。Email:zhanglili@cnooc.com.cn
  • 基金资助:

    国家科技重大专项(2016ZX05024-004-004、2016ZX05024-002-008)资助。

Eocene-Oligocene sedimentary environment evolution and its impact on hydrocarbon source conditions in eastern Pearl River Mouth Basin

Zhang Lili, Shu Yu, Cai Guofu, Long Zulie, Liu Dongqing, Wang Fei   

  1. Research Institute of Shenzhen Branch of CNOOC China Limited, Guangdong Shenzhen 518067, China
  • Received:2018-07-10 Revised:2018-11-23 Online:2019-07-25 Published:2019-07-15

摘要:

综合利用已钻井沉积物中的微体古生物化石(孢粉、藻类、有孔虫、钙质超微化石)记录和有机地球化学指标等,分析珠江口盆地东部始新世-渐新世海侵的历史过程及其对烃源岩的影响。研究结果表明:早中始新世文昌组沉积期(文昌期),盆地沉积以陆相湖泊-三角洲沉积体系为主,沉积物中古生物以陆相孢粉、高含量的淡水藻类化石为主,但盆地南部荔湾凹陷和东部的韩江凹陷个别层段沉积物中出现海相标志的有孔虫和钙质超微化石,说明该时期这两个凹陷遭遇过海侵,该时期烃源岩以中深湖-浅湖相泥岩为主,为湖生低等植物源、富含无定型有机质、I-Ⅱ1型干酪根;晚始新世恩平组沉积期(恩平期),盆地北部各凹陷仍以陆相浅水湖泊-河流三角洲沉积体系为主,沉积物中古生物以陆相孢粉为主、含少量淡水藻类化石,但盆地南部的荔湾凹陷则以海相陆架沉积为主,整套地层中可见海相微体古生物化石,泥岩有机地球化学分析显示含三芳甲藻甾烷,白云凹陷在恩平期末遭受海侵影响,该时期烃源岩以陆源高等植物源、富含煤质、Ⅲ型干酪根为主;渐新世珠海组沉积期(珠海期),早期盆地北部珠一坳陷为剥蚀区,未接受沉积,珠二坳陷沉积以三角洲-滨岸-陆架沉积体系为主,珠海期中-晚期,随着海平面上升,整个盆地沉没于海平面之下,接受古珠江三角洲-陆架-陆坡沉积,此时期仅白云凹陷海相泥岩成熟,为有效的烃源岩,其余地区泥岩由于埋深和地温等原因,尚未成熟。沉积记录中微体古生物组合和有机地球化学指标很好地记录了始新世以来构造活动强度影响下珠江口盆地沉积环境的演变过程及对烃源条件的影响,对盆地东部、南部低勘探程度区的资源潜力有重要的类比分析意义。

关键词: 珠江口盆地, 始新世, 沉积环境, 微体古生物, 烃源条件

Abstract:

The microlithic paleontological fossils (spore, algae, foraminifera, and calcareous microfossils) recorded in drilled sediments and organic geochemical indicators are comprehensively used to analyze the Eocene-Oligocene transgression history process in the Pearl River Mouth Basin (east) and its impact on source rocks. The results show that in the sedimentary period of Wenchang Formation in the Early Middle Eocene (Wenchang Period), the basin sediments are dominated by the continental lake-delta sedimentary system, and the paleophytes in the sediments are mainly terrestrial sporopollen and high-content fresh water algae fossils. However, the marine markers of foraminifera and calcareous microfossils appear in the sediments of Liwan Depression in the southern basin and Hanjiang Depression in the east, indicating that these two depressions encountered transgression during this period, when source rocks are mainly composed of medium-deep lake-shallow lake facies, formed by lacustrine lower plants, rich in amorphous organic matter and type I-Ⅱ1 kerogen. In the sedimentary period of late Eocene Enping Formation (Enping Period), the depressions in the northern basin are still dominated by the continental shallow lake-river delta sedimentary system. The paleophytes in the sediments are mainly terrestrial sporopollen, containing a small amount of fresh water algae fossils. However, the Liwan Depression in the southern basin is mainly composed of marine shelf deposits, and marine micropaleontology fossils can be seen in the whole set of strata, containing triaryldinostanes as indicated by the organic geochemical analysis of mudstones. Baiyun Depression was affected by transgression at the end of Enping Period. During this period, the source rocks were dominated by terrestrial high plants, rich in coal-bearing type Ⅲ kerogen. During the sedimentary period of Oligocene Zhuhai Formation (Zhuhai Period), the Zhu Ⅱ Depression in the northern basin during the early period was an ablation zone without accepting sedimentation, but the Zhu Ⅱ Depression was deposited as a delta-shore-shelf sedimentary system. In the middle-late period of Zhuhai, with the sea level rising, the whole basin sank under the sea and accepted the paleo-Pearl River Delta-continental shelf-continental slope sediment. During this period, only the marine mudstone of Baiyun Depression was mature as effective source rocks. The mudstones in the area were not yet mature due to burial depth and ground temperature. The micro-paleontological assemblages and organic geochemical indicators in the sedimentary records well recorded the evolution of the sedimentary environment in the Pearl River Mouth Basin and the impact on hydrocarbon source conditions under the influence of tectonic activity intensity since the Eocene, which is of great significance to the analogy analysis on the resource potential of the low exploration area in the eastern and southern basin.

Key words: Pearl River Mouth Basin, Eocene, sedimentary environment, microfossils, hydrocarbon source conditions

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