川南五峰组-龙马溪组页岩岩相特征及沉积作用  

Shale Facies Characteristics and Sedimentation of the Wufeng Formation-Longmaxi Formation in the Southern Sichuan Basin

作　　者：刘雨迪 梁超 操应长[1,2] 吴靖[3] 韩豫 谢浩然 罗子良 马哓月 LIU YuDi;LIANG Chao;CAO YingChang;WU Jing;HAN Yu;XIE HaoRan;LUO ZiLiang;MA XiaoYue(School of Geosciences,China University of Petroleum(East China),Qingdao,Shandong 266580,China;Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao,Shandong 266580,China;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国石油大学(华东)深层油气重点实验室,山东青岛266580 [3]山东科技大学地球科学与工程学院,山东青岛266590

出　　处：《沉积学报》2024年第5期1832-1848,共17页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41902134,42172165);中央高校基本科研业务费专项资金(22CX06001A);泰山学者工程(TSQN201812030)。

摘　　要：【目的】川南地区上奥陶统和下志留统黑色页岩是页岩气勘探的主要目标,探究此套页岩的岩相划分、沉积环境以及沉积过程,可为页岩气勘探开发提供理论依据。【方法】通过岩心、光学显微镜以及扫描电镜的观察与分析,根据矿物组成及含量、沉积构造特征,并综合考虑生物作用及成岩作用对岩相进行划分;利用氧化—还原指标(U/Th、V/Cr、V/(V+Ni)、Ni/Co)、海平面变化指标(Ce^(*))、水体滞留程度指标(Mo/TOC)、古气候指标(Sr/Cu)、古盐度指标(Sr/Ba)以及古生产力指标(Cu、生源Ba)对古环境进行分析,并基于岩心和薄片观察、X射线荧光扫描以及矿物X衍射全岩分析对沉积过程进行识别。【结果】五峰组—龙马溪组页岩识别出六种岩相:生物硅质页岩、黏土质页岩、(长英质—钙质)粉砂页岩、钙质粉砂页岩、钙质页岩以及长英质粉砂页岩。沉积环境自下而上经历五个阶段的变化。五峰组—龙马溪组页岩主要是在低能条件下悬浮沉积形成,也在五峰组中部和龙马溪组下部发育上升流沉积,五峰组顶部发育少量风暴流沉积,在龙马溪组上部也见有重力滑塌、碎屑流、和浊流沉积。【结论】沉积环境的频繁变化以及沉积过程的多样性控制了岩相的类型与特征,进一步导致不同岩相的有机质含量、孔隙度、含气量等储层品质因素存在显著差异,后续仍需在页岩岩相与储层品质等方面加强研究,为页岩气的勘探与开发提供理论依据。[Objective and Methods]The black shales of the Upper Ordovician and Lower Silurian in the southern Sichuan Basin are the main target of shale gas exploration,having attracted extensive attention among domestic and foreign scholars.To provide the theoretical basis for shale exploration and development in the future,the lithofacies division,sedimentary environment,and depositional processes of shale are explored.Through core observation and analysis using optical and scanning electron microscopes,the lithofacies are divided based on mineral composition and content,sedimentary structural characteristics,and comprehensive consideration of biological process and diagenesis.The paleoenvironment is analyzed by oxidation-reduction(U/Th,V/Cr,V/(V+Ni),Ni/Co),sea level change(Ce*),hydrographic restriction(Mo/TOC),paleo-climate(Sr/Cu),paleo-salinity(Sr/Ba),and paleo-productivity(Cu,biogenic Ba)indices.Depositional processes are identified by core and thin section observation,X-ray fluorescence scanning,and mineral X-ray diffraction whole rock analysis.[Results]Six lithofacies are identified from the shales of the Wufeng Formation-Longmaxi Formation:biological siliceous,clayey,(felsic-calcareous)silty,calcareous silty,calcareous,and felsic silty shale.The shale sedimentary environment of the Wufeng Formation-Longmaxi Formation underwent five stages of bottom-up changes.The paleo-climate shifted from warm and humid at the bottom of the Wufeng Formation to dry and hot at the middle to dry and cold at the top,and then from dry and hot at the lower part of the Longmaxi Formation to warm and humid at the middle and upper sections.In the lower parts of the Wufeng and Longmaxi formations,the sea level had risen owing to two large-scale transgressions.When the sea level is high,the extent of basin retention is weak,strong in reduction,low in salinity,and high in paleo-productivity.The glacier event at the top of Wufeng Formation caused the sea level to drop.When the sea level is low,the extent of basin retention is strong,weak in red

关 键 词：五峰组—龙马溪组 岩相特征 古环境 沉积过程 沉积模式 

分 类 号：P618.13[天文地球—矿床学]