砂质辫状河心滩坝的发育演化过程探讨——沉积数值模拟与现代沉积分析启示  

Discussion on Evolution of Bar in Sandy Braided River: Insights from sediment numerical simulation and modern bar

作　　者：张可[1] 吴胜和[1] 冯文杰[1] 郑定业 喻宸 刘照玮 

机构地区：[1]中国石油大学(北京)地球科学学院油气资源与探测国家重点实验室,北京102249 [2]中国石化石油勘探开发研究院,北京100083

出　　处：《沉积学报》2018年第1期81-91,共11页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41372116);国家重大科技专项(2011ZX05009-003)~~

摘　　要：心滩坝作为辫状河中一种重要的沉积单元,国内外学者基于地下储层、露头、现代沉积进行了大量研究,但并未建立完整的心滩坝发育演化模式,明确心滩坝两侧辫状水道对其的影响。因此,采用沉积数值模拟技术(Delft3D)再现心滩坝的生长与演化过程,并且通过现代沉积相互验证,建立了心滩坝演化模式。研究表明:1)心滩坝的演化过程可划分为三个阶段,心滩坝的形成、生长及向下游方向迁移,心滩坝的侧向迁移,"坝尾沉积"及复合心滩坝的形成;2)由于两侧辫状水道的冲刷作用,心滩坝头部两侧均遭受侵蚀,表现为坝体向下游方向迁移,随着发育演化时间的增长,向下游迁移速率逐渐减小,最终坝体稳定;3)心滩坝中下部由于两侧辫状水道的不对称性,一侧侵蚀,一侧沉积,心滩坝侧向迁移;4)沉积物在心滩坝尾部卸载,形成"坝尾沉积",其发育程度取决于两侧辫状水道水动力强度,水动力越强,"坝尾沉积"越发育,随着"坝尾沉积"的不断延长,最终充填心滩坝之间的辫状水道,形成复合心滩坝。The sandy braided rivers are widely distributed in the continental facies basin and the bar is important as a sedimentary unit. Domestic and overseas scholars have done researches based on the reservoirs,outcrop and modern sediments. However,no pattern of bar evolution has been built and the influence of braided channel on bar has not been clarified. Therefore,the paper uses the sediment numerical simulation to reproduce the evolution of bar,and verify through modern sediments,and finally build the pattern of bar evolution. The research shows that,firstly,the bar evolution can be divided into three stage,including the formation,growth and migration of the bar,lateral migration of the bar and the formation bar tail which lead to compound bar. Secondly,the head of the bar is eroded by the braided channel,which leads bar migration to downstream. As evolution time goes on,migration rate reduces gradually,and then the bar stabilizes on the position. Thirdly,because of the asymmetry of braided channel,sediment deposits on one side and sediment erodes on another side of the bar. The bar migrates laterally. At last,the sediment deposits on the tail of the bar and the bar tail formed. The length of the bar tail reveals the discharge of channel. The larger the discharge of channel is,the longer bar tail is. The elongation of bar tail induces the closure the braided channel and forms compound bar.

关 键 词：砂质辫状河 沉积数值模拟 心滩坝 辫状水道 演化过程 

分 类 号：P343.1[天文地球—水文科学]