新疆克拉玛依油田三叠系克下组冲积扇内部构型

Internal architecture of alluvial fan in the Triassic Lower Karamay Formation in Karamay Oilfield,Xinjiang

应用研究区丰富的密井网和邻近露头资料,探讨了新疆克拉玛依油田三叠系克下组冲积扇内部构型单元的层次划分系统,并建立相应的沉积构型模式。在冲积扇的扇根、扇中和扇缘各亚相带,进一步划分了3个级次的构型要素以表达其内的沉积复杂性。扇根亚相主要由主槽、片流带和漫洪带组成,其中,在主槽内主要发育槽流砾石(岩)体(可细分为砾石坝和流沟)与泥石流沉积,在片流带内主要发育片流砂砾体(可细分为砾石坝和流沟),在漫洪带主要发育漫洪砂体和漫洪细粒沉积,总体构型样式以广泛分布的砾石坝夹含流沟和漫洪沉积的"泛连通体"为特征;扇中亚相主要由辫流带和漫流带组成,其中,辫流带的主体构型要素为辫流水道(可细分为砂坝和沟道),总体构型样式为复合宽带状辫流水道砂体与漫流细粒沉积侧向相间、垂向互层为特征;扇缘亚相主要由径流带和漫流带组成,其中,径流带的主体构型要素为径流水道,总体构型样式以窄带状径流水道和漫流砂体镶嵌于漫流—湿地泥岩之中为特征。

Based on abundant borehole data of close-spacing wells and outcrop analogue,this paper mainly deals with the hierarchical system of internal architecture of alluvial fan and establishes the corresponding architectural model in the Triassic Lower Karamay Formation in Karamay Oilfield.Three orders of architectural elements are divided in each subfacies belt within alluvial fan to further demonstrate its depositional complexity.Inner fan,which can be dividied into main trench,sheet-flood belt,and overbank,is characterized by main trench-fill and sheet-flood sand-gravel deposits with thin discrete fine layer,resulting in a kind of pano-connective sand-gravel body.And in the main trench,gravel body（gravel bar and gulley deposits）and debris flow deposits are developed.In the sheet-flood belt,sand-gravel deposits（gravel bar and gulley deposits）are developed.In the overbank belt,sandbody and fine deposits are developed.Middle fan,which can be divided into braided-stream belt and overbank,is characterized by the pattern of lateral apartment and vertical interbedding of channel sand-gravel deposits with overbank fine ones.Braided fluvial belt mainly consists of braided channels,which can be divided further into sandy bar and gulley deposit.Outer fan,which can be divided into runoff belt and marshy,is characterized by narrow-belt runoff channel sandbodies inlaid into overbank and/or marshy mudstone.