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以层序地层学理论为指导,通过对岩芯、地震、测井、录井以及分析化验等资料的综合研究,建立了海拉尔盆地乌尔逊凹陷南屯组层序地层格架。将南屯组划分为2个三级层序和7个四级层序;并对层序格架内的沉积相划分和沉积体系进行了研究,确定该区主要发育扇三角洲、辫状河三角洲、湖底扇和湖泊沉积4种沉积体系。扇三角洲主要分布在乌西陡坡带,辫状河三角洲分布在乌东、乌北、乌南缓坡带,湖底扇主要分布在乌南和乌北洼槽中心的深湖相中,而湖泊主要分布在凹陷的中心及扇三角洲、辫状河三角洲的侧翼,从凹陷边缘到中心,沉积相由扇三角洲、辫状河三角洲沉积逐渐变为滨浅湖、深湖—半深湖沉积,整体呈南北分异、东西成带的格局。不同时期的沉积特征、沉积相展布表现各异,总体表现出水体由浅变深,再变浅,沉积范围逐渐扩大,扇三角洲、辫状河三角洲呈先退积,后进积的特点。通过对沉积相的精细研究,为该区下一步油气的勘探与开发奠定了基础。
Guided by the theory of sequence stratigraphy, the sequence stratigraphic framework of the Nantun Formation in the Wuerxun Depression of the Hailar Basin is established through a comprehensive study of core, seismic, logging, well logging and analytical laboratory data. The Nantun Formation is divided into two third-level sequences and seven fourth-level sequences. The division and depositional system of sedimentary facies in the sequence framework are studied, and the main developed fan delta, braided river delta , Sublacustrine fan and lake sedimentary system of four kinds of deposition. The fan delta mainly distributes in the steep slope of the Uxig basin. The braided river delta distributes in the gentle slope belt of Wudong, Wubei and Wunan. The sublacustrine fan is mainly distributed in the deep lacustrine facies in the center of Wunan and Wubei depression, while the lakes are mainly distributed In the center of the sag and the fan delta, the flanks of the braided river delta, from the edge of the depression to the center, the sedimentary facies gradually change into the shallow lake and the semi-deep lake sediments by the deposition of fan delta and braided river delta, Differentiation, something into a pattern. Sedimentary characteristics and sedimentary facies distribution in different periods show different characteristics, showing that the water body changes from shallow to deep and then shallow, and the sedimentary range gradually expands. The fan delta and braided river delta are characterized by sedimentation and sedimentation. Through the careful study of sedimentary facies, it laid the foundation for the exploration and development of the next oil and gas in the area.