湖平面变化背景下指状砂坝型浅水三角洲沉积响应过程:基于水槽沉积模拟实验  

Sedimentary Response of a Fingered Bar-Type Shoal Water Delta to Lake Level Fluctuations:Insights from Flume Tank Experiments

作　　者：任大伟[1] 魏思源 尹太举[1] 陈少伟 房久顺 赵文凯 REN Dawei;WEI Siyuan;YIN Taiju;CHEN Shaowei;FANG Jiushun;ZHAO Wenkai(School of Geosciences,Yangtze University,Wuhan,Hubei 430100,China;School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;Tianjin Branch of CNOOC China Limited,Tianjin 300459,China;Drilling and Production Technology Research Institute,Qinghai Oilfield Company,PetroChina,Dunhuang,Gansu 736202,China)

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]中国地质大学(北京)能源学院,北京100083 [3]中海石油(中国)有限公司天津分公司,天津300459 [4]中国石油青海油田公司钻采工艺研究院,甘肃敦煌736202

出　　处：《现代地质》2024年第6期1511-1522,共12页Geoscience

基　　金：国家自然科学基金项目(41672119);国家自然科学基金重点项目(42130813)。

摘　　要：指状砂坝型浅水三角洲是由一个或多个河口坝-天然堤-河道组成的指状坝构成,它发育在水体较浅、构造相对稳定、水平面频繁波动的湖(海)盆中。为探究频繁湖水位变化与指状砂坝型浅水三角洲发育的关系及其内部沉积单元的形成过程与响应机制,利用水槽模拟实验正演还原了湖水位频繁升降条件下指状砂坝型三角洲的发育演化过程。实验设计18个期次的洪-枯水期的湖平面周期性变化,耗时108 h,利用3D激光扫描仪进行精准的沉积地貌监测和定量沉积学分析。研究发现:指状砂坝型浅水三角洲自下而上发育底积层-前积层-顶积层;河道、河口坝、天然堤彼此相互关联、相互影响,河道携带沉积物在河口形成河口坝,河口坝淤积叠置并逐渐转化为天然堤,稳固的天然堤降低了河道摆动频率,使得河道能携带沉积物不断向湖区延伸搬运;单一河道的指状砂坝型浅水三角洲发育受控于河道、天然堤及河口坝三者建设关系的动态平衡,水位和流量的周期性旋回加速了这一平衡关系的建立;指状砂坝型浅水三角洲的发育过程中,沉积物主要堆积在河口,河道呈条带状剥蚀,河口两侧泥沙卸载速率不一致导致了河道左右摆动。通过实验数据分析总结出湖水位变化背景下指状砂坝型浅水三角洲的沉积响应过程及其内部单元的动态演化规律,为研究浅水三角洲演化过程及该类油气藏勘探开发提供重要参考。The finger-bar-type shoal water delta is composed of one or more finger bar composed of mouth bar-natural levee-river channel.This type of delta develops in lake or sea basins with shallow water bodies,relatively stable tectonics,and frequent horizontal fluctuations.This study aims to explore the relationship between frequent lake level fluctuations and the development of finger-bar-type shoal water deltas,along with the formation and response mechanism of their internal sedimentary units.A flume tank experiment was conducted to simulate the development and evolution of bar finger under conditions of frequent lake level rise and fall.The simulation experiments were designed for a 18-cycle model of lake level fluctuations during alternating flood and dry periods.The experiment lasted 108 hours,involving precise monitoring of sedimentary geomorphology and quantitative sedimentological analysis using a 3D laser scanner.The river channel,mouth bar,and natural levee are interrelated and interact with one another.The river channel carries sediments that form a mouth bar at the river mouth,which gradually accumulates and transforms into a natural levee.The solid natural levee reduces the frequency of channel oscillation,allowing the river channel to continuously transport and extend sediments into the lake area.The development of a single-channel finger-bar-type shoal water delta is controlled by the dynamic balance among the river channel,natural levee,and mouth bar,as well as the periodic water level cycles.Additionally,the flow accelerates the establishment of this balanced relationship.The development of the finger-bar-type shoal water delta is characterized by sediment accumulation primarily at the river mouth and strip-like denudation of the river channel.Inconsistent sediment unloading on either side of the estuary cause the river channel to oscillate from side to side.The analysis of the experimental data reveals changes in the sedimentary response of the finger-bar-type shoal water delta.The study summarized th

关 键 词：浅水三角洲 指状砂坝 水槽实验 沉积演化 

分 类 号：P618.13[天文地球—矿床学]