摘要
在海相细粒沉积岩中建立高精度层序地层格架可有效预测富有机质发育层段及优质非常规油气储层,格架的建立是目前非常规油气沉积学和细粒层序地层学中的研究难点。本文以川北陡山沱组细粒沉积岩为研究对象,选取典型剖面,通过野外露头精细描述和薄片高精度分析,在陡山沱组浊积序列段和细粒沉积段划分出块状粗砂岩、层理砂岩、富砂质夹层粉砂岩、滑塌揉皱粉砂质泥岩、粒序韵律粉砂质泥岩、断续砂质纹层泥岩和暗纹层泥岩7种“沉积构造+岩性”分类模式的岩相类型;在上部混积序列段划分出细晶云岩、钙质砂岩、球粒灰岩组成的浅水混积岩相组合,以及泥晶灰岩与钙质泥岩形成的深水混积岩相组合,并以此为基础自下而上识别了斜坡相、缓坡相、深水陆棚相、浅水陆棚相、混积潮坪相和混积陆棚相6类沉积相;通过野外露头观察,识别出4个三级层序界面,包括陡山沱组砂岩与南沱组冰碛岩的岩相突变面SB1、冲刷侵蚀面SB2、岩相转换面SB3和SB4;根据岩相叠加样式及沉积构造定量统计,在陡山沱组中划分了56个准层序,18个准层序组,总结了重力流控准层序、浪控缓坡准层序、浪控陆架准层序和混积准层序等4类准层序样式,识别了9个体系域,划分出3个完整的三级层序单元(SQ1-SQ3)和顶部海侵体系域(TST4);结合沉积相和层序特征,认为川北陡山沱组经历了“陡斜坡—缓坡—陆棚—混积台地”填平补齐的演化过程。
Establishing a high-precision sequence stratigraphic framework in marine fine-grained sedimentary rocks is important for an effective prediction of organic-rich intervals and high-quality unconventional oil/gas reservoirs which is still a challenge in unconventional oil/gas sedimentology and fine-grained sequence stratigraphy.Taking the fine-grained sedimentary rocks of the Doushantuo Formation in northern Sichuan as the research object typical sections are selected.Through detailed field investigation of outcrops and high-precision analysis of thin sections,the turbidite sequence section and fine-grained sedimentary section of the Doushantuo Formation are divided into 7 lithofacies types according to sedimentary structure and lithology:(1)massive coarse sandstone,(2)bedding sandstone,(3)sand-rich-interlayer siltstone,(4)collapse-crumpled silty mudstone,(5)grain-rhythmic silty mudstone,(6)intermittent sandy laminar mudstone,and(7)dark-laminar mudstone.The upper mixed sediments are divided into shallow-water mixed lithofacies which include fine-grained dolomite,calcareous sandstone,and spherulitic limestone,and deep-water mixed lithofacies including micrite limestone and calcareous mudstone.On this basis,six types of sedimentary facies are identified from bottom to top:slope facies,gentle-slope facies,deep-water shelf facies,shallow-water shelf facies,mixed tidal-flat facies,and mixed shelf facies.Through field outcrop observation,four third-order sequence boundaries are identified:lithofacies catastrophe surface SB1 of Doushantuo Formation sandstone and Nantuo Formation moraine;scouring contact surface SB2;and lithofacies transformation surfaces SB3 and SB4.According to lithofacies superposition style and sedimentary structural types,56 parasequences and 18 parasequence sets are delineated;four types of parasequence styles-gravity-flow/wave-controlled gentle slope,wave-controlled shelf and mixed parasequences-are summarized;9 system tracts are identified;and three complete third-order sequence units(SQ1-SQ3)and t
作者
匡明志
李一凡
樊太亮
张坦
刘旺威
刘楠
KUANG Mingzhi;LI Yifan;FAN Tailiang;ZHANG Tan;LIU Wangwei;LIU Nan(College of Energy,Chengdu University of Technology,Chengdu 610059,China;School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;Wuxi Institute of Petroleum Geology,Sinopec Petroleum Exploration and Development Research Institute,Wuxi 214035,China;Research Institute of Shaanxi Yanchang Petroleum(Group)Co.,Ltd.,Xi’an 710075,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2023年第4期164-181,共18页
Earth Science Frontiers
基金
国家自然科学基金联合基金项目(U19B6003-01-02)
国家自然科学基金面上项目(42272173)。
关键词
川北坳陷
陡山沱组
细粒沉积
岩相
高频层序
Northern Sichuan depression
Doushantuo Formation
fine-grained sedimentation
lithofacies
high-frequency sequence
