川东南地区下三叠统飞仙关组层序地层与鲕滩展布特征研究

在川东南地区，以层序地层学原理为指导，通过综合分析野外露头剖面和钻井等资料，分析了飞仙关组和鲕滩的发育特征。飞仙关组发育完整，可以识别出两个三级层序底界面，均为Ⅱ型层序的岩性、岩相转换面。第1层序海侵期主要发育混积陆棚环境，从第1层序高位期开始研究区进入碳酸盐岩台地演化阶段，鲕粒滩开始发育。第1层序高位期至第2层序高位早期，主要为开阔台地沉积环境，灰岩和鲕粒灰岩为主要岩石类型；第2层序高位晚期，沉积局限台地环境的紫红色泥页岩、白云岩夹石膏层。鲕粒滩主要发育于第1层序高位期和第2层序高位早期。第1层序高位期鲕滩呈北西—南东向展布，第2层序高位早期鲕滩则为北东—南西向展布。鲕粒滩分布以第2层序高位早期较佳，为潜在的最有利勘探层位。

Sequence stratigraphy and oolitic beach distribution of lower Triassic Feixianguan formation in southeastern Sichuan Basin

Guided by principle of sequence stratigraphy,by comprehensively analyzing field outcrop profile and drilling data,the development characteristics of Feixianguan formation and oolitic beach reservoirs in southeastern Sichuan Basin were analyzed.The Feixianguan formation develops completely,the bottom boundaries of two third-order sequence (SQ1 and SQ2) can be recognized,which both are lithologic and lithofacies conversion interface of Ⅱ type sequence.The SQ1 mainly develops mixed shelf during transgressive period.At the beginning of high systems tract (HST) of the SQ1,the environment of the research area changes into carbonated platform evolution period,and oolitic beaches begin to develop.From HST of SQ1 to the early HST of SQ2,the environment of the area is mainly of open platform,the rock is mainly of micrite and oolitic limestone.During the late HST of SQ2,purple mudstone,shale and gypsum interbedded dolomite deposits within restricted platform.Oolitic beaches mainly develop in the HST of SQ1 and the early HST of SQ2.The oolitic beaches distribute northwest-southeast during the HST of SQ1 and distribute northeast-southwest in the early HST of SQ2.The oolitic beaches have best distribution characteristics in the early HST of SQ2,and the reservoirs of this period are the most favorable potential exploration target.