摘要
四川盆地东部(川东)红星地区上二叠统吴家坪组具备良好的页岩气成藏条件,是四川盆地二叠系页岩气勘探的重要接替领域,但对于该套硅泥质烃源岩的形成机理目前仍缺乏明确的认识。除了岩石矿物组成、地球化学成分、宏体化石组合等特征之外,以放射虫为代表的微体化石对于辨别硅质泥页岩沉积的成因也具有重要意义。放射虫是显生宙海洋浮游生态系统的重要组成部分,其组合可以指示沉积环境,而其丰度是古海洋生产力的良好指标。利用酸蚀法分离出放射虫化石,从而鉴别化石的形态组合特征并结合薄片镜下统计,分析了放射虫丰度与总有机碳(TOC)含量的相关性。研究结果表明,川东红星地区HY3井吴家坪组吴二段中发育大量放射虫化石,经鉴定为泡沫虫目和内射球虫目分子,属于典型的浅水放射虫组合(Se组合)。镜下统计表明吴二段放射虫丰度与TOC含量呈现较好的相关性。通过放射虫组合特征,结合吴家坪组沉积序列和古地理背景,推断吴二段烃源岩形成于水深小于60 m的较浅水环境。吴二段有机质富集可能受到初级生产力、氧化还原条件、陆源碎屑输入、上升流等多方面因素的影响,其中高古生产力是吴二段有机质富集的主控因素之一。
[Objective]The upper Permian Wujiaping Formation in the Hongxing area of eastern Sichuan Province has good shale gas accumulation conditions and is also an important successor for Permian shale gas exploration in the Sichuan Basin.However,the formation mechanism of these siliceous-argillaceous source rocks is still unclear.Apart from their petromineralogical characteristics,geochemical composition and macrofossil assemblage(represented by radiolarian)are also important for identifying the genesis of this siliceous-argillaceous source rock.[Methods]Radiolarian is a significant planktonic component of the Phanerozoic marine ecosystem.Various radiolarian assemblages indicate different sedimentary environments,and their abundance is a good indicator of palaeoproductivity.In this study,radiolarians were separated by the acid-etching method to identify different morphological characteristics,and the correlation between radiolarian abundance and total organic carbon(TOC)content was also analysed through thin-section observation.[Results]A large number of radiolarians were found in the Wujiaping Formation in the Well HY3 in the Hongxing area of eastern Sichuan Province.These fossils were identified as Spumellaria and Entactinaria,belonging to a typical shallow-water radiolarian assemblage,namely,the Se assemblage.In the Second Member of the Wujiaping Formation,the radiolarian abundance exhibited a relatively positive correlation with the TOC content.[Conclusion]Based on the radiolarian assemblage characteristics,sedimentary sequence and palaeogeographic background of the Wujiaping Formation,it is inferred that these source rocks from the Second Member of the Wujiaping Formation formed in a shallow-water environment less than 60 m deep.The accumulation of organic matter in the Second Member of the Wujiaping Formation was probably affected by primary productivity,redox conditions,terrigenous debris input and upwelling,among which high palaeoproductivity was one of the main controlling factors.
作者
易雨昊
包汉勇
朱红涛
陆亚秋
孟志勇
李凯
陈发垚
YI Yuhao;BAO Hanyong;ZHU Hongtao;LU Yaqiu;MENG Zhiyong;LI Kai;CHEN Fayao(Exploration and Development Research Institute,SINOPEC Jianghan Oilfield Company,Wuhan 430223,China;School of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,China;School of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,China)
出处
《地质科技通报》
CAS
CSCD
北大核心
2024年第4期167-180,共14页
Bulletin of Geological Science and Technology
基金
中国石油化工股份有限公司科研项目“红星二叠系页岩气有效开发关键技术研究”(P22045)
2022-2023年度湖北省博士后创新实践岗位资助项目。
关键词
吴家坪组
红星地区
放射虫组合
有机质富集
古生产力
总有机碳(TOC)
Wujiaping Formation
Hongxing area
radiolarian assemblage
organic matter accumulation
paleoproductivity
total organic carbon(TOC)
