鄂尔多斯盆地西南部长7油层组深水重力流沉积岩相特征及分布模式  

Lithofacies Characteristics and Distribution Patterns of Deep Water Gravity Flow Deposits in the Chang 7 Oil Member in the Southwest Ordos Basin

作　　者：王林 吕奇奇[1] 张严 周浩 张蕾 罗奥 陈乐康 WANG Lin;LÜQiQi;ZHANG Yan;ZHOU Hao;ZHANG Lei;LUO Ao;CHEN LeKang(School of Geosciences,Yangtze University,Wuhan 430100,China)

机构地区：[1]长江大学地球科学学院,武汉430100

出　　处：《沉积学报》2025年第1期154-168,共15页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42102170);长江大学国家级大学生创新创业训练计划项目(202210489002)。

摘　　要：【目的】鄂尔多斯盆地三叠系延长组长7油层组广泛发育深水重力流沉积,然而其岩相分布规律、沉积演化过程及沉积模式研究较为薄弱,制约了该区深水油气勘探部署。【方法】以盆地西南部长7油层组为研究对象,依据大量岩心、测录井、薄片鉴定、电镜扫描、粒度数据分析、X射线衍射全岩分析以及矿物鉴定分析等资料,对研究区深水重力流沉积岩石类型、岩相特征、岩相组合、岩相分布特征以及沉积相划分等进行分析,并在此基础上建立了重力流沉积模式。【结果】(1)研究区岩性以灰色、褐灰色细粒级砂岩,灰色、深灰色极细—粉级砂岩,暗色、黑色泥页岩为主,夹少量凝灰岩;矿物成分主要由石英、长石及黏土矿物组成;(2)主要岩相类型包括块状层理细砂岩相(Sm)、正粒序粉砂—细砂岩相(Sa)、条带状(粉砂质)泥岩相(Mh)、似块状泥岩相(Mm)、水平纹层页岩相(Sh)、凝灰岩相(T)等6种岩相类型,并根据不同沉积环境的发育情况总结出四种岩相组合类型:Sm-Mh(Sh)、Sm-Sa-Mh(Sh)、Sa-Mh(Sh)、T-Sh(Mm),反映湖泊相环境中砂质碎屑流—深水原地沉积、砂质碎屑流—浊流—深水原地沉积、浊流—深水原地沉积、火山碎屑沉积—深水原地沉积作用;(3)依据不同类型重力流发育的岩相组合及平面分布特征,认为从坡折带以下至湖盆中心,重力流呈现砂质碎屑流、砂质碎屑流—浊流、浊流的演化特征;(4)依据砂质碎屑流砂体所占重力流砂体比例、岩相类型、岩相组合、自然伽马(GR)曲线形态和水道规模等因素,将重力流沉积划分为限制性水道、非限制性水道、前端朵体三个亚相。【结论】该研究有助于明确长7油层组优质砂体发育规律并预测其分布,为研究区非常规油气的勘探开发提供指导。[Objective]Deep-water gravity flow deposits are widely developed in the Chang 7 oil member of the Triassic Yanchang Formation in the Ordos Basin.However,the research on the distribution pattern of lithofacies,sedimentary evolution process,and depositional model is relatively weak,which restricts the deployment of deep-water oil and gas exploration in this area.[Methods]Taking the Chang 7 oil member in the southwestern Ordos Basin as the research object,based on a large number of cores,well logging,thin section identification,electron micro-scope scanning,particle size date analysis,X-ray diffraction whole rock analysis,mineral identification analysis,and other data,the rock types,lithofacies characteristics,lithofacies assemblages,distribution characteristics,and sedimentary facies division of the deep-water gravity flow deposits were analyzed.Then,the gravity flow depositional model was established.[Results](1)The lithology of deep-water gravity flow deposits of the Chang 7 oil member is mainly composed of gray and brown-gray fine-grained sandstone,gray and dark gray ultrafine-powder sandstone,and dark and black mud shale,with a small amount of tuff;the mineral components are mainly composed of quartz,feldspar,and clay minerals;(2)the main lithofacies types include massive bedding fine sandstone facies(Sm),positive-order silt-fine sandstone facies(Sa),banded(silty)mudstone facies(Mh),laminated shale facies(Sh),block like mudstone facies(Mm),and tuff facies(T).According to the development of different sedimentary environ-ments,four lithofacies assemblages are summarized:Sm-Mh(Sh),Sm-Sa-Mh(Sh),Sa-Mh(Sh),and T-Sh(Mm).This reflects sandy debris flow-deep water in situ deposition,sandy debris flow-turbidity currents-deep water in situ deposition,turbidity currents-deep water in situ deposition,and volcaniclastic deposits-deep water in situ deposition in the lacustrine environments;(3)based on the lithofacies assemblages and plane distribution characteristics developed by different types of gravity flow deposits,from

关 键 词：岩相特征 沉积相划分 深水重力流 长7油层组 鄂尔多斯盆地 

分 类 号：P512.2[天文地球—地质学]