摘要：

干旱型分支河流体系规模较大、砂体发育,可形成大规模油气储集层,是国内外学者关注和研究的热点领域。文中以干旱型分支河流体系为研究对象,通过水槽沉积模拟实验研究了其动态演化过程、沉积特征及内部构型样式。研究表明: 在干旱型分支河流体系中,朵体是基本的沉积单元,其沉积演化在整个体系的形成和发展中占据核心地位。根据形成过程,可以将朵体划分为侧积型、摆动型、加积型3种类型,其构型特征在剖面上分别呈侧向、无序和垂向堆叠,朵体的发育位置、规模与形态也具有明显差别。其中,侧积型朵体主要发育于扇体侧缘,其面积、长度、宽度均较大,长宽比和宽厚比也较大,形态偏扇形; 摆动型朵体主要发育于扇体前缘,其面积、长度、宽度及其长宽比和宽厚比同样较大,平面上呈扇形; 加积型朵体主要发育于扇根两侧,其面积与长度、宽度均相对较小,长宽比及宽厚比也相对较小,呈舌型。干旱型分支河流体系演化过程中存在“水道下切→朵体前积→朵体侧向迁移→朵体溯源迁移→水道再次下切”的自旋回过程,该过程在分支河流体系演化的不同阶段表现出一定的规律性和周期性。研究结果对分析干旱型分支河流体系的沉积过程、沉积特征、内部构型等具有一定的参考意义。

关键词: 干旱型分支河流体系, 水槽实验, 沉积演化, 朵体类型, 沉积构型, 自旋回过程

Abstract:

Arid distributive fluvial systems (ADFS) have attracted considerable academic interest due to their large spatial extent and potential for hydrocarbon reservoir development. This study focuses on the arid distributive fluvial system, analyzing its dynamic evolution, depositional characteristics, and internal configuration through flume experiments. The findings are as follows: (1) In arid distributive fluvial systems, lobes act as the fundamental depositional building blocks, exerting primary control over system formation and evolution. (2) Based on their formation processes, lobes can be categorized into three types: lateral, oscillating, and accretionary. In cross-sectional view, these types display characteristic stacking patterns: lateral, irregular, and vertical, respectively. Lateral lobes develop primarily along the fan margins and are characterized by large area, length, and width, with high aspect and width-to-thickness ratios and a lobate geometry. Oscillatory lobes occur at the fan front, sharing similar dimensions and morphology. In contrast, accretionary lobes are smaller, develop near the fan apex, and exhibit lower aspect and width-to-thickness ratios, with a tongue-shaped geometry. (3) Throughout the evolution of the arid distributive fluvial system, a cyclical process of 'channel incision-lobe front accumulation-lobe lateral migration-lobe backward migration-channel re-incision' is observed, demonstrating regularity and periodicity at various stages of the system's evolution. These findings enhance the understanding of sedimentary processes, internal architectures, and spatial evolution within arid distributive fluvial systems, and offer guidance for reservoir prediction in analogous depositional settings.

Key words: arid distributive fluvial system, flume experiment, sedimentary evolution, lobe type, sedimentary configuration, autogentic cycle

中图分类号: 

• P512.2