摘要： 扇三角洲是一类非常重要的油气聚集场所,准确可靠的扇三角洲沉积模式,对储集层预测具有重要意义。准噶尔盆地玛北地区三叠系百口泉组发育一套扇三角洲沉积体系,虽然前人做了大量的研究,但在沉积模式方面仍存在一些争议。通过现代沉积考察、前人水槽模拟实验、研究区测井、岩心等资料综合分析发现: (1)玛北地区百口泉组扇三角洲平原发育3类微相,即辫状河道微相、砾质漫滩微相、水上朵前泥微相,同时可见泥石流沉积;玛北地区百口泉组扇三角洲前缘发育2种微相,即砾质浅滩微相、砂质浅滩微相,同时可见碎屑流沉积;(2)扇三角洲平原河道与河道间均为砂砾岩,河道砂砾岩的分选性明显好于河道间砂砾岩;(3)扇三角洲前缘不发育水下分流河道,扇三角洲前缘的砂砾岩主体是由扇三角洲平原片流入湖形成的,呈席状。

关键词: 扇三角洲, 沉积模式, 准噶尔盆地, 玛北地区, 百口泉组

Abstract: Fan deltas are important reservoirs for hydrocarbon accumulation. A reliable depositional model of fan deltas is an essential guide for reservoir prediction. The Lower Triassic Baikouquan Formation in Mabei area of Junggar Basin is characterized by the development of fan-delta systems. Although a lot of studies have been done,it is still controversial about the depositional model of fan delta. Based on a comprehensive analysis of modern depositional systems, flume experiment and a subsurface dataset from the Mabei area,it is found that: (1)In fan-delta plain,three types of depositional microfacies,including braided channel,conglomeratic overbank and subaerial outer-fan mud,have been identified,and debris flow deposits exists;in fan-delta front,two types of depositional microfacies,including conglomerate shoal and sandy shoal,have been identified,and subaqueous debris flow deposits exists;(2)In fan-delta plain,channel and inter-channel are dominated by coarse-grained deposits without muddy deposits,and the deposits of channel is better sorted than inter-channel;(3)Fan delta front is dominated by sheet-like,coarse-grained deposits from sheet flow.

Key words: fan delta, depositional model, Junggar Basin, Mabei area, Baikouquan Formation

中图分类号: 

• P512.2