东非鲁伍马盆地中始新统深水沉积特征及层序界面识别方法  

Deep-water sedimentary characteristics and sequence boundary identification of Middle Eocene in Rovuma Basin,East Africa

作　　者：孙辉 范国章 王红平 丁梁波 左国平 马宏霞 庞旭 许小勇 SUN Hui;FAN Guozhang;WANG Hongping;DING Liangbo;ZUO Guoping;MAHongxia;PANG Xu;XU Xiaoyong(PetroChina Hangzhou Research Institute of Petroleum Geology,Hangzhou 310023,China)

机构地区：[1]中国石油杭州地质研究院,杭州310023

出　　处：《岩性油气藏》2023年第6期106-116,共11页Lithologic Reservoirs

基　　金：中国石油天然气集团有限公司科技项目“海外深水、超深水油气勘探关键技术研究”(编号:2021DJ2403)资助。

摘　　要：以层序地层学经典模式为指导,利用岩心、测井、录井及地震资料,总结了东非鲁伍马盆地深水区中始新统三级和四级层序界面特征,将深水沉积中发育的水道-朵体复合体与沉积相对应,划分了沉积亚相和微相,并在此基础上探讨了深水沉积的演化规律及其对储层的影响。研究结果表明:①鲁伍马盆地中始新统三级层序顶界位于凝缩段和偶发的碳酸盐碎屑流顶部,底界为逐期南向迁移的重力流底界;四级层序由半深海泥岩顶界和地震剖面上连续性好的沉积界面确定,但仅可以在水道-朵体复合体分布范围内开展解释。②研究区深水沉积可识别出水道复合体和朵体复合体2种沉积相,复合水道、朵体、决口扇和溢岸/漂积沉积4种亚相,水道轴部/边部充填、内天然堤、块体搬运沉积(MTD)、水道底部滞留沉积、朵体单元主体/边缘、决口扇和溢岸/漂积沉积等9种沉积微相;决口扇和溢岸/漂积沉积均分布于复合水道的北侧,受底流影响的决口扇在平面上呈向北发散的脉状。③研究区中始新统深水沉积的演化分为SQ1—SQ4共4个阶段,整体表现为先进积、后退积的过程,水道-朵体复合体受重力流与底流交互作用影响,逐期向南迁移。④研究区储层的发育主要受控于沉积微相,朵体单元主体和水道轴部充填微相发育的储层品质好,其中朵体单元主体微相中储层最发育、物性最好,孔隙度为13.00%~21.00%,渗透率为5.0~118.0 mD,水道轴部充填微相次之,储层孔隙度为13.00%~19.00%,渗透率为0.8~23.0 mD;溢岸/漂积沉积微相中发育的储层物性差,决口扇不发育储层。Guided by the classic model of sequence stratigraphy,using core,welllog,mudlog and seismic data,the characteristics of the third-order and fourth-order sequence boundaries of Middle Eocene in the deep-water area of Rovuma Basin in East Africa were summarized.Corresponding to channel-lobe complexes in deep-water depo-sits,sedimentary subfacies and microfacies were divided.Based on this,the evolution laws of deep-water deposits and the influence of sedimentary microfacies on reservoirs were explored.The results show that:(1)The top boundary of the third-order sequence of Middle Eocene in Rovuma Basin is located at the top of the condensed section and occasional carbonate debris flow,and the bottom boundary is located at the bottom of the gravity flow that migrates southward in stages.The fourth-order sequence is determined by the top boundary of the bathyal deposit and the sedimentary interface with good continuity on the seismic section,but can only be interpreted within the distribution range of the channel-lobe complexes.(2)Two sedimentary facies,including channel complex and lobe complex,have been identified in deep-water deposits in the study area.The two sedimentary facies can be subdivided into four subfacies:composite channel,lobe,crevasse splay,and overbank/drift deposits.There are nine microfacies,including channel axis/edge filling,internal natural levee,mass transport deposits(MTD),channel bottom lag deposit,lobe element main body/edge,crevasse splay,and overbank/drift deposits.Both crevasse splay and overbank/drift deposits are distributed in the northern part of the composite channel,and the crevasse splay affected by bottom flow is in a northward divergent vein shape.(3)The evolution of deep-water depo-sits of Middle Eocene in the study area can be divided into four stages,namely SQ1-SQ4 in sequence,showing a process of progradational deposition and retrograde deposition as a whole.Affected by the interaction between gravity flow and bottom current,the channel-lobe complexes gradually migrated southw

关 键 词：深水沉积 重力流 底流 复合水道-朵体 决口扇 层序界面 中始新统 东非鲁伍马盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]