川东北元坝地区上三叠统须家河组沉积特征研究

Sedimentary Character of Upper Triassic Series Xujiahe Formation in Yuanba Area of Northeastern Sichuan

川东北元坝地区须家河组沉积特征一直认为以湖相沉积为主,缺少大型河流三角洲沉积体系。综合应用钻井、岩心、露头、分析测试数据及地震资料对该地区上三叠统须家河组沉积特征进行系统研究,发现元坝地区沉积与前人认识存在较大差异;其一元坝地区地层特征与周边地区特征相似,岩性上可以划分5个岩性段,其中须一段、须三段、须五段以细粒沉积为主,可作为全区地层对比划分的标志层;其二须二、须四段发育辫状河三角洲沉平原-前缘沉积体系,辫状河道沉积极为发育,是研究区储层发育的主要层位;其三河流三角洲沉积的物源来至北偏东向的米仓山造山带,而不是前人认为的龙门山造山带,这种近源补给模式是研究区发育大型河流三角洲沉积建造的关键因素。

Some geologists thought that sediment type of upper Triassic series Xujiahe formation is lacustrine facies,not large-scale river-delta sediments in Yuanba area of northeastern Sichuan.These viewpoint may not correct according to ours recent research in the area.Founding analysing wells,rock core,outcrop,seismic data that Xujiahe formation stratigraphic character in Yuanba is similar to other areas that strata can be divided 5 rock section.Section 1,3,5 is mud-siltstone and correction mark in basin.Section 2,4 is sandstone and large-scale braided river delta plain-dalta front including braided channel-main reservoir,Key of river delta sediments formed is provenance that come from Micang mountain orogenic belt,not Longmen mountain orogenic belt.