川西北地区中三叠统雷口坡组沉积相再认识  

New understanding of sedimentary facies of the Middle Triassic Leikoupo Formation in northwestern Sichuan Basin

作　　者：何利 刘建清 隆轲[2] 谭钦银 宋晓波[2] HE Li;LIU Jianqing;LONG Ke;TAN Qinyin;SONG Xiaobo

机构地区：[1]中国地质调查局成都地质调查中心(西南地质科技创新中心) [2]中国石化西南油气分公司 [3]自然资源部沉积盆地与油气资源重点实验室

出　　处：《海相油气地质》2023年第4期371-380,共10页Marine Origin Petroleum Geology

基　　金：中国石化西南油气分公司项目“川西地区雷口坡组勘探潜力评价”(编号:34450000-20-ZC06070-0033)资助。

摘　　要：基于区域构造背景分析,通过钻井岩心观察、露头剖面调查和薄片鉴定,以及露头-连井剖面对比、骨干地震剖面解释,深化了川西北地区雷口坡组构造-沉积特征及沉积相演化的认识。研究认为:①川西北部江油—绵竹一带雷口坡期处于沉降-沉积中心,晚三叠期坳陷向南扩展至峨眉垮洪洞一带。②雷口坡组自西向东发育台地边缘相、局限台地相及蒸发台地相。台地边缘相发育浅滩亚相,主要包括砂屑滩、鲕粒滩微相;局限台地相由浅滩、潮坪及潟湖亚相组成,包括砂屑滩、藻云坪、灰云坪、潮道、淡化潟湖、咸化潟湖、半咸化潟湖等微相;蒸发台地相由蒸发坪及盐湖亚相组成,主要发育膏坪、云膏坪、膏云坪、云坪,膏质盐湖及石盐盐湖等微相。③台缘浅滩规模大,颗粒为致密的内碎屑及鲕粒;台内滩规模较小,颗粒类型主要为藻屑。建立了雷口坡组“台地边缘相—局限台地相—蒸发台地相”沉积模式,沉积变迁受到沉积基底向西北倾斜的背景及海侵-海退旋回的控制。Based on the analysis of regional tectonic background,the understanding of tectonic-sedimentary characteristics and sedimentary facies evolution of Leikoupo Formation in northwestern Sichuan Basin has been deepened through drilling core observation,outcrop profile investigation,thin section identification,outcrop-well profile correlation and typical seismic profile interpretation.The results show that:(1)The uplift of the Xuefengshan ancient land during the Leikoupo period of the Middle Triassic intensified the geographical background of“low west,high east”in the Upper Yangtze sea.With the continuous uplifting of the Luzhou palaeohigh and Kaijiang palaeohigh,the subsidence center and depocenter during the Leikoupo period was formed in Jiangyou-Mianzhu area of northwestern Sichuan Basin,and in Late Triassic the depression extended southward to the Kuahongdong area of Emei County.(2)Controlled by the geographical background and sea level change,three major sedimentary facies,i.e.,platform margin facies,limited platform facies,and evaporite platform facies,are developed from west to east in Leikoupo Formation.Shoal subfacies is developed in the platform margin facies,which mainly consists of sandy shoal and oolitic shoal microfacies.The limited platform facies consists of shoal,tidal flat and lagoon subfacies,including sandy shoal,algae limestone flat,calcareous dolomite flat,tidal channel,desalinated lagoon,saline lagoon,brackish lagoon,and other microfacies.The evaporite platform facies is composed of evaporite flat and salt lake subfacies,with microfacies of gypsum flat,gypsum-dolomite flat,dolomitegypsum flat,dolomite flat,gypsum-salt lake and halite lake developed in them.(3)The platform margin shoal has a significant scale with densely packed internal clastic and oolitic grains.Conversely,the internal shoal has a smaller scale primarily characterized by algae debris particles.We propose a sedimentary model of"platform margin facies-limited platform facies-evaporite platform facies"in the Leikoupo Formation

关 键 词：沉积特征 沉积演化 沉积模式 雷口坡组 川西北 

分 类 号：TE122.2[石油与天然气工程—油气勘探]