新疆博斯腾湖北缘现代冲积扇与扇三角洲平原分支河流体系的沉积特征与意义

辫状分支河流体系的展布特征能够更好地预测有利储层发育位置。位于新疆焉耆盆地博斯腾湖北缘的黄水沟冲积扇和清水河扇三角洲平原发育典型的分支河道,形成分支河流体系。基于野外勘察和沉积露头的详细观察,从"源"到"汇"分析黄水沟冲积扇和清水河扇三角洲平原中分支河流体系辫状河道的沉积特征和控制因素,将黄水沟冲积扇划分为3个区带、清水河扇三角洲平原划分为4个区带。不同区带沉积特征的变化主要表现为沉积物卸载量减少、粒径随搬运距离的增加而降低、水动力减弱、河道宽度变窄。分支河流体系所显示的河道沉积范围比单个河道相模式更大,在有利储层预测方面具有一定的优势。在现今干旱气候与构造背景相同的条件下,物源的供给、河流的卸载量、沉积物的扩散能力和扇体的坡度等是控制冲积扇和扇三角洲分支河流体系沉积差异的主要因素。

Sedimentary characteristics and significance of distributive fluvial system of modern alluvial fan and fan delta plain in the northern margin of Bosten lake,Xinjiang

The distribution characteristics of distributive fluvial system can help accurately predict the location of favorable reservoir.Typical branch channels are developed in the Huangshuigou alluvial fan and the Qingshuihe fan delta plain at the northern margin of Bosten lake in Yanqi Basin of Xinjiang, thus forming a distributive fluvial system. Based on detailed observations of sedimentary outcrops and field surveys, the sedimentary characteristics and controlling factors for braided channels of the distributive fluvid system in the Huangshuigou alluvial fan and the Qingshuihe fan delta plain are analyzed from "source" to "sink". The Huangshuigou alluvial fan is divided into three zones, and the Qingshuihe fan delta plain is divided into four zones. The variation of sedimentary characteristics in different zones is mainly manifested by the decrease of sediment unloading and hydrodynamic force, the decreasing particle size with the increasing of transport distance, and the narrowing of river channel. The distributive fluvial system shows a larger sedimentary range than a single channel phase, presenting certain advantages in favorable reservoir prediction. Under the same conditions of current arid climate and tectonic setting, the supply of provenance, unloading of rivers, sediment diffusion, and slope of the fan are the main factors controlling the sedimentation differences between alluvial fans and fan delta distributive fluvial systems.