川中北部通江地区上三叠统香溪群沉积相研究

Research on Sedimentary Facies of the Upper Triassic Xiangxi Formation in Tongjiang Area of the North of Central Sichuan

四川盆地上三叠统香溪群(有的称香溪组或须家河组)是盆地内主要天然气储层之一,近年来勘探形势喜人。通过对四川北部通江地区上三叠统香溪群沉积环境的研究,结合地层和岩石学特征,加之通江地区上三叠统香溪群时四川盆地各周缘山系为构造活动期,因此认为上三叠统香溪群的沉积环境为湿地扇相、河流相和湖泊相的沉积组合,物源经冲积扇、河流搬运入湖,发育砾质坝、沙砾质坝、沙质坝、滨湖、浅湖相的滩、坝与滨岸沙、泥坪、沼泽微相等。同时,根据研究区各有关时代的沉积相、亚相、微相的划分及特征,将研究区内沉积环境及相的发育演化特征综合成湿地冲积扇-辨状河、曲流河-湖泊环境演化的综合沉积相展布模式。

Xiangxi formation of the upper Triassic in Sichuan basin is one of main reservoir bed for natural gas in this basin. The exploration situation is gratifying in recent years. According to the study of depositional environments of this formation, combining with the characters of formation and petrology, we think that the sedimentary facies of this formation is the depositional association of the humid fan facies, river facies and lacustrine facies. Material sources are moved into the lake by alluvial fans and rivers. Gravelly bars, sandy and gravelly bars, sandy bars, shore lakes, shoals of shallow lake fans, bars and onshore sands, mud terraces, and marsh microfacies are developed; moreover, by the classification and character of the sedimentary facies, subfacies and microfacies of each related epoch in the investigation area, we sum the sedimentary environment and characters of development and evolution of facies in this area up as a aggregative model of the humid alluvial fan-braided river and meander-lacustrine environment evolution.