准噶尔盆地西北缘辫状河沉积模式探讨——以七区下侏罗统八道湾组辫状河沉积为例

摘要

Braided-stream deposits are the major depositional system of lower Jurassic in the northwestern margin,Junggar Basin.Based on observation and description of cores,thin-section identification,assay and analysis,and well logging of Badaowan Formation,lower Juassic in No.7 area of Xinjiang oil field,the depositional markers＇ features of braided stream were generalized in which rock types are simple such as;the maturity of rock is low;rock compositions are complicate;plant residue carbides locally concentrate into stratiform;sedimentary structures are plentiful;there is a dual structure that a top layer and a bottom layer vertically overprint and many sand-bodies form pan communicated sandbody.This parper further analysed the changes of color,rock,granularity,sedimentary structure and logging responses in vertical depositional associations of braided stream,which is interpreted as a sequence of channel lag deposit,mid-channel bar and flood plain.Using the spatial distribution of microfacies,it summarized the facies model of braided stream of Badaowan Formation,lower Juassic in No.7 area.These results have vital significance for progressive exploration and adjusted development of oil field.%准噶尔盆地西北缘下侏罗统下部地层主要发育辫状河沉积。以新疆油田七区下侏罗统八道湾组为例,以岩芯观察为基础,综合利用薄片鉴定、分析化验以及测井解释等资料,分析认为该区辫状河的沉积鉴别标志为：岩石类型比较单一;岩石成分复杂,成熟度较低,局部常见富集成层的碳屑;沉积构造丰富,具有＂二元结构＂;砂体具有＂泛连通体＂结构等。在此基础上,进一步从颜色、岩性、粒度、沉积构造和测井曲线特征等方面剖析了河床滞留、心滩和泛滥平原等微相的沉积特征,并结合沉积微相的空间分布规律,探讨了研究区的辫状河沉积模式。该研究成果对油田的滚动勘探和开发调整都具有重要意义。