扇三角洲流体类型转换及控制因素分析——以青海希里沟扇三角洲为例  

Fluid Transformation and Controlling Factors of the Fan Delta:A case study of the Xiligou delta in Qinghai

作　　者：冯烁 李顺利[1] 于兴河[1] 付超 高明轩 刘倩 FENG Shuo;LI ShunLi;YU XingHe;FU Chao;GAO MingXuan;LIU Qian(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;CNOOC Research Institute,Beijing 100028,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中海油研究总院,北京100028

出　　处：《沉积学报》2024年第2期643-660,共18页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42272124);中央基本科研业务费(2-9-2019-100)。

摘　　要：【目的】扇三角洲广泛发育于沉积盆地边缘及内部,具有规模庞大、类型多样、生储盖配置良好等特点,蕴藏着巨大的油气资源勘探潜力。然而,其流体类型转换和控制因素、沉积过程与特征仍尚不清晰。【方法】以青海希里沟扇三角洲为研究对象,基于野外露头和探槽剖面的精细刻画描述,综合利用14C测年、粒度分析等方法,对希里沟扇三角洲不同时期沉积物粒度、结构、沉积构造等方面特征进行研究。【结果与结论】通过野外露头探槽剖面的精细刻画描述共划分出9类岩相及7种垂向组合序列,识别出碎屑流、片状洪流和牵引流共3种流体类型。根据AMS14C定年标定沉积界面、沉积物粒度、结构等方面特征,将希里沟湖三角洲划分为SI、SII和SIII共3个阶段,其中SI期为碎屑流粗粒沉积期,SII为片状洪流改造沉积期,SIII期为牵引流改造沉积期。通过沉积物粒度敏感组分分析,在希里沟湖扇三角洲平面识别出3期朵叶。结合希里沟三角洲沉积地形坡度和青海湖15 ka以来孢粉浓度变化,证实了希里沟扇三角洲流体类型转换受控于沉积坡度与气候的变化,明确了扇三角洲上平原以碎屑流主导,发育碎屑流主水道、片状洪流沉积为主要的构型单元,扇三角洲下平原以片状洪流主导,发育以辫状水道、辫流坝以及洪漫沉积为主要的构型单元,扇三角洲前缘以牵引流主导,发育以水下分流河道、河口坝以及席状砂为主要的构型单元。[Objective]Fan deltas are widely developed in the margins and interior of sedimentary basins,with a large scale,diverse types,and idea source-reservoir-caprock association,and have huge exploration potential for oil and gas resources.However,its fluid type transition and controlling factors,sedimentary process and characteristics of the fan deltas are still unclear.[Methods]Taking the Xiligou fan delta in Qinghai Province as the research object,based on the fine description of outcrop and trench profiles,the characteristics of grain size,structural characteristics of sediments in the Xiligou fan delta during different periods were studied by comprehensive use of 14C dating and grain size analysis.[Results and Conclusions]Through the fine description of the field outcrop trough section,9 types of lithofacies and 7 vertical combination sequences are divided,and 3 types of fluid types including debris flow,sheet flood and traction flow are identified.According to AMS14C dating,the Xiligou Lake delta is divided into three stages,SI,SII,and SIII by calibrating the characteristics of the sedimentary interface,sediment grain size,and structure.The SI stage is a coarse-grained sedimentary stage of clastic flow,and the SII stage is the deposition of sheet-flood reformation.Stage SIII is the period of traction flow reformation and deposition.Based on the analysis of sedimentary particle size-sensitive components,three lobe stages were identified in the delta plane of Xiligou Lake.A comprehensive analysis of the Xiligou delta slopes and the changes in the sporopollenin concentration in Qinghai Lake since 15 ka shows that the fuid type conversion of the Xiligou fan delta is controlled by the changes in the sedimentary slope and climate.The debris flow channel and sheet flooding sediments are the main architectural units.The lower plain of the fan delta was dominated by sheet flooding,and braided channels,braided bar,and flood-diffusion sediments were the main architectural units.The front of the fan delta was dominated by tr

关 键 词：扇三角洲 沉积过程 流体类型 气候变化 控制因素 

分 类 号：P512.2[天文地球—地质学]