摘要
上扬子地区下寒武统页岩展现出了良好的页岩气勘探前景,是中国乃至全球开展古老层系海相页岩气勘探研究的重要领域。利用高分辨率层序地层学方法在海相细粒沉积岩中建立高精度层序地层格架,对川西南地区下寒武统进行层序划分与对比,可有效预测富有机质发育层段,指导非常规油气勘探。本文以川西南地区下寒武统麦地坪组-筇竹寺组细粒沉积岩为研究对象,选取金石103井,通过岩心精细描述和高精度薄片分析,将麦地坪组-筇竹寺组划分为磷质岩、弱纹层硅质泥岩、硅质粉砂质泥岩、变形层理泥质粉砂岩、块状硅质粉砂岩、暗纹层粉砂质泥岩、透镜状粒序泥质粉砂岩、波状纹层泥质粉砂岩、贫纹层粉砂质泥岩、富纹层泥质粉砂岩和钙质胶结硅质粉砂岩等11种岩相类型,并以此为基础识别了混积潮坪、泥质深水陆棚、砂泥质深水陆棚、泥质浅水陆棚和砂泥质浅水陆棚5类沉积相;通过岩心精细观察,识别出了3个三级层序界面,包括震旦系-寒武系不整合面SB1、麦地坪组-筇竹寺组岩性突变面SB2和岩性组合转换面SB3。根据岩相叠加样式及沉积构造定量统计,在麦地坪组-筇竹寺组中划分了35个准层序、14个准层序组,总结了由潮汐流控主导的“磷质颗粒灰岩+磷质-钙质砂岩+钙质-磷质泥质粉砂岩”(HST1准层序单元)、受重力流和底流协同作用的“钙质胶结粉砂岩+块状粉砂岩/变形层理泥质粉砂岩+暗纹层粉砂质泥岩”(HST2准层序单元)、受风暴浪作用为主导底流作用协同影响的“透镜状粒序泥质粉砂岩/波状纹层泥质粉砂岩/变形层理泥质粉砂岩+暗纹层粉砂质泥岩”(TST3准层序单元)和受波浪与重力流共同影响的“钙质胶结粉砂岩+富纹层状泥质粉砂岩+贫纹层状粉砂质泥岩”(HST3准层序单元)等4类典型准层序叠加样式,识别了6个体系域,划分出3个完整的三级层�
The Lower Cambrian shale in Upper Yangtze has good shale gas prospects and is of great importance for the exploration and research of deep marine shale gas in China and even in the world.This paper carried out high-resolution sequence-stratigraphic analysis of the fine-grained marine sediment rocks in the Lower Cambrian,southwestern Sichuan to establish a high-precision sequence-stratigraphic framework of the rock formation which can be used,by sequence comparison analysis,to effectively predict the organic-rich intervals and guide unconventional oil and gas exploration in the region.The fine-grained sedimentary rocks of the Lower Cambrian Maidiping-Qiongzhusi Formations in well Jinshi 103 were examined through elaborate core description and high-precision thin section analysis.The rock formations were divided into 11 lithofacies types:phosphatic rocks;weak-laminar siliceous mudstone;siliceous silty mudstone;deformed bedding argillaceous siltstone;massive siliceous siltstone;dark-laminar silty mudstone;lenticular sequence argillaceous siltstone;wavy lamellar argillaceous siltstone;lean laminated silty mudstone;laminar-rich argillaceous siltstone;and calcareous cementation siliceous siltstone.On this basis,five sedimentary facies types were identified:mixed tidal flat;muddy deep-water shelf;sandy argillaceous deep-water shelf;muddy shallow-water shelf;and sandy muddy shallow-water shelf.By fine core observation,three third-order sequence boundaries—Sinian-Cambrian unconformable surface,SB1,and lithological interfaces between contrasted lithologies,SB2,and between lithologic assemblages,SB3,within the studied rock formation—were identified.Based on quantitative statistical analysis of lithofacies superposition styles and sedimentary structures,35 parasequences and 14 parasequence sets were delineated in the studied rock formation.Four parasequence superposition styles were summarized:“phosphorite grainstone+calcareous phosphatic sandstone+calcareous phosphatic argillaceous siltstone”parasequence unit(HST1)c
作者
袁钰轩
李一凡
樊太亮
杜伟
陈格格
张坦
匡明志
刘旺威
YUAN Yuxuan;LI Yifan;FAN Tailiang;DU Wei;CHEN Gege;ZHANG Tan;KUANG Mingzhi;LIU Wangwei(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100083,China;College of Energy,Chengdu University of Technology,Chengdu 610059,China;Wuxi Institute of Petroleum Geology,Petroleum Exploration and Development Research Institute,SINOPEC,Wuxi 214035,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2023年第6期162-180,共19页
Earth Science Frontiers
基金
国家自然科学基金联合基金项目“海相深层油气富集机理与关键工程技术基础研究(U19B6003-01-02)”
国家自然科学基金面上项目“古气候-古环境高频协同演化作用下的富有机质页岩形成机制:以中上扬子地区陡山沱组为例(42272173)”。
关键词
川西凹陷
麦地坪组-筇竹寺组
细粒沉积
岩相
高频层序
western Sichuan depression
Maidiping-Qiongzhusi Formations
fine-grained sediments
lithofacies
high-frequency sequence
