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珠江口盆地陆丰南地区文昌组沉积古环境恢复及烃源岩有机质富集主控因素研究 被引量:3

Sedimentary paleoenvironment and main controlling factors of organic enrichment in source rocks of the Wenchang Formation in southern Lufeng,Pearl River Mouth Basin
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摘要 文昌组为陆丰南地区主力烃源岩发育层段,为了恢复文昌期沉积古环境,探讨优质烃源岩有机质富集主控因素,选用166组文昌组泥岩样品的主、微量元素测试数据,采用元素地球化学方法,在研究区首次详尽分析文昌期不同次洼、不同层段的古盐度、古气候、古水深和古氧相的纵横向演变规律,并探讨部分钻井出现盐度异常的原因及三芳甲藻甾烷、球藻对古环境的指示意义,结合TOC、古生产力和陆源输入变化研究,明确了研究区优质烃源岩的主控因素。结果表明:陆丰南地区始新统文昌组沉积期水体以淡水环境为主,局部层段盐度微弱增加,垂向上,从文四段向文一+二段水体盐度逐渐降低,横向上,文四段沉积期,陆丰15洼水体盐度最高,文三段—文一+二段沉积期,陆丰13东洼水体盐度较高。推测陆丰南地区文昌组水体盐度变化受到海侵影响,文四段沉积期,海侵影响主要集中在陆丰15洼,文三段沉积期,海侵影响扩大至陆丰15洼和陆丰13东洼东侧,进入文一+二段沉积期,受海侵影响程度较小。球藻及三芳甲藻甾烷在研究区不能作为水体咸化或者海侵的判别指标,球藻含量变化与古气候、古生产力、古水深关系密切,受古盐度变化影响有限。陆丰南地区文四段沉积期古气候温湿,古水深最大,还原性最强,进入文三段、文一+二段,气候温湿程度、水深和还原性均有所降低;文四段沉积期陆丰13东洼水深最大,其次为陆丰15洼,还原性陆丰13东洼最强,其次为陆丰13西洼。文昌组烃源岩有机质富集主要受控于古生产力和古陆源输入,其次受古气候和古水深控制,古氧相变化对有机质富集控制作用较弱,高古生产力主导着文昌组优质烃源岩的形成及分布,主要发育生产力富集模式。 The Wenchang Formation is the main source rock development interval in the southern Lufeng area.In order to restore the sedimentary paleoenvironment of the Wenchang period and explore the main controlling factors of organic enrichment in high-quality source rocks,the major and trace element data of 166 mudstone samples from the Wenchang Formation are analyzed.The elemental geochemical method is used to analyze the paleosalinity,paleoclimate,paleowater depth and the vertical and horizontal evolution of the paleo-oxygen phases in different subsags and different intervals of the Wenchang period for the first time in the study area.The causes of salinity anomalies in some wells and the indicative significance of triaromatic steranes and chlorella to the paleoenvironment are discussed;combined with TOC,paleoproductivity and terrestrial input changes,the main controlling factors of high-quality hydrocarbon source rocks in the study area are clarified.The results show that the water body of the Eocene Wenchang Formation is mainly freshwater during the deposition period,with slight increase in salinity in the local layer.Vertically,the salinity of the water body gradually decreases from the 4 th to the 1 st+2 nd members of the Wenchang Formation;horizontally,water salinity is highest in the Lufeng 15 subsag during deposition of the 4 th member,and relatively high in the Lufeng 13 eastern subsag during deposition of the 3 rd to the 1 st+2 nd members.It considers the change in water salinity in the Wenchang Formation is due to transgression effect,where water transgression is mainly concentrated in the Lufeng 15 subsag during deposition of the 4 th member,and expands to the eastern Lufeng 15 subsag and Lufeng 13 eastern subsag during deposition of the 3 rd member.Granodiscus and triaromatic dinoflagellate sterane cannot be used as indicators of water salinization or transgression in the study area.The change in Granodiscus content is closely related to paleoclimate,paleoproductivity and paleowater depth,but not much affect
作者 何雁兵 雷永昌 邱欣卫 肖张波 郑仰帝 刘冬青 HE Yanbing;LEI Yongchang;QIU Xinwei;XIAO Zhangbo;ZHENG Yangdi;LIU Dongqing(Shenzhen Branch of CNOOC Ltd.,Shenzhen 518054,China;CNOOC Deepwater Development Ltd.,Shenzhen 518054,China)
出处 《地学前缘》 EI CAS CSCD 北大核心 2024年第2期359-376,共18页 Earth Science Frontiers
基金 中海油重大生产科研项目“珠江口盆地(东部)浅水区古近系油气成藏条件及勘探突破方向(SCKY-2020-SZ-21)”。
关键词 陆丰凹陷 文昌组 元素地球化学 沉积古环境 光面球藻 古生产力 烃源岩 Lufeng Sag Wenchang Formation element geochemistry sedimentary palaeoenvironment Granodiscus paleoproductivity source rocks
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