辫状河三角洲沉积特征与生长演变规律——水槽沉积模拟实验研究  

Sedimentary characteristics and evolution of a braided river delta———Insights from a flume experiment

作　　者：何艺玮 房元龙 冯文杰[1] 刘远航 范洋 郭华粘 张佩 贾风娟 HE Yiwei;FANG Yuanlong;FENG Wenjie;LIU Yuanhang;FAN Yang;GUO Huazhan;ZHANG Pei;JIA Fengjuan(School of Earth Sciences,Yangtze University,Wuhan,430100;Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao,Shandong,266071;University of Chinese Academy of Sciences,Beijing,100049;Research Institute of Petroleum Exploration&Development,Qinghai Oilfield Company,Dunhuang,Gansu,736202)

机构地区：[1]长江大学地球科学学院,武汉430100 [2]中国科学院海洋研究所海洋地质与环境重点实验室,山东青岛266071 [3]中国科学院大学,北京100049 [4]中石油青海油田分公司勘探开发研究院,甘肃敦煌736202

出　　处：《地质论评》2023年第4期1564-1580,共17页Geological Review

基　　金：国家自然科学基金资助项目“砂质辫状河心滩坝沉积构型模式与沉积动力学机制研究”(编号:41802123)的成果~~。

摘　　要：辫状河三角洲是一类常见的沉积体系,也是一类常见的油气储层,其沉积特征、沉积演化过程及内部结构一直受到沉积学研究的关注。为明确辫状河三角洲沉积特征、演化过程及生长演变规律,笔者等通过水槽实验模拟辫状河三角洲在平缓的水下底形上逐步发育的过程,并采用三维激光扫描仪、延时拍照等手段进行精准的沉积地貌监测和定量沉积学分析。研究表明:(1)辫状河三角洲沉积演化过程中,三角洲的规模、水流分散样式、沉积体表面地貌特征及沉积物分布样式存在阶段性差异,可据此将实验辫状河三角洲的演化分为3个阶段。(2)在最初阶段,辫状河携带沉积物直接入“湖”堆积并形成朵状河口坝,入“湖”水流无明显的水道化特征,随着朵状河口坝逐渐堆积露出水面,三角洲平原初步形成,平原上河道开始分流并导致后续河口坝转变为连续的弧形坝分布于先期沉积体周缘,这一阶段三角洲平均半径快速增加;进入第二阶段后,三角洲平均半径增速减缓,供给河道进入三角洲平原后形成1~2条主干分流河道与多条次级分流河道,并在主干河道河口区形成弧形的前缘朵体;到第三阶段,三角洲平原面积已经较大,其平均半径增速进一步降低,平原上分流河道的分叉性更强、宽度更小,不同分流河道规模接近并可同时将沉积物输送到三角洲前缘多个部位发生沉积,在同一时期形成多个孤立的小规模的前缘朵体。(3)在整个沉积演化过程中,伴随着三角洲规模的逐渐增大,分流河道的宽度逐步减小、流程变长、分流河道数量逐步增加,三角洲前缘沉积由少量弧形的连续分布朵体转变为多个孤立分布的小规模朵体。(4)在第二、三阶段,分流河道表现为多个侵蚀—回填的自旋回演化过程,形成了多套自旋回沉积复合体。(5)辫状河三角洲前积层存在自下而上、由近向远表现为沉Objective:Braided river delta is a common sedimentary system and a common oil and gas reservoir.Its sedimentary characteristics,sedimentary evolution process and internal structure have always been concerned by sedimentology research.Methods:An experimental braided river delta was simulated above a flat bedform.The sedimentary process and topography were recorded with a time-lapsed camera and a 3D laser scanner.Quantitively sedimentary process analysis was performed to investigate the sedimentary characteristics,evolution process and internal sedimentary architecture of the experimental braided river delta.Results:①In the evolution of the braided river delta,its dimension,flow pattern,surface morphology and sediment distribution showed three stages of differences.②In the initial stage,the braided river carried sediment directly into the“lake”and a lobe-shaped mouth bar was constructed.The water flowing into the lake does not have channelization characteristics.As the flower-shaped mouth bars gradually accumulated and emerged from the water surface,the delta plain was initially formed,and the river channels on the plain began to diverge,causing the subsequent mouth bars to transform into continuous arc-shaped bars distributed around the edge of the previous sedimentary body.The average radius of the delta increased rapidly at this stage.After entering the second stage,the growth rate of the average radius of the delta slows down,one or two main distributary channels and multiple secondary distributary channels were formed,and an arc-shaped lobe was formed in the river mouth area of the main channel.By the third stage,the area of the delta plain was larger,and its average radius growth rate was further reduced.The distributary channels on the plain were more bifurcated and smaller in width.Distributary channels were similar in scale and could transport sediments to the delta front at the same time.Deposition occurred in many parts of the delta edge,and multiple isolated small-scale mouth bars were formed in

关 键 词：辫状河三角洲 水槽实验 沉积特征 演变规律 内部结构 

分 类 号：P343.5[天文地球—水文科学] P512.2[天文地球—地球物理学] TV148[水利工程—水力学及河流动力学]