珠江口盆地顺德凹陷始新世古气候古环境及烃源岩发育模式  

Paleoclimate,paleoenvironment and source rock development model of Eocene in Shunde Sag,Pearl River Mouth Basin,China

作　　者：裴健翔 金秋月 范代军 雷明珠 PEI Jianxiang;JIN Qiuyue;FAN Daijun;LEI Mingzhu(CNOOC Hainan Branch Company,Haikou 570312,China)

机构地区：[1]中海石油(中国)有限公司海南分公司,海口570312

出　　处：《石油勘探与开发》2025年第2期306-319,共14页Petroleum Exploration and Development

基　　金：中海油研究项目“顺德凹陷构造差异演化下成烃成藏条件分析及有利勘探方向研究”(SCKY-2023-HN-3)。

摘　　要：基于岩矿学、测井、地震、古生物、地球化学等资料的综合分析,开展珠江口盆地西南部边缘凹陷顺德北凹始新统文昌组二段烃源岩的古环境、古气候条件精细研究和烃源岩模式构建。研究表明:①文昌组二段发育厚层优质湖相烃源岩,纵向非均质强,平均总有机碳含量(TOC)为4.9%,从下到上可划分为3个地层单元:Ⅰ单元发育Ⅰ型有机质为主的优质烃源岩,有机质主要来自湖泊生物贡献,TOC值平均为5.9%;Ⅱ单元发育Ⅱ_(2)型有机质为主的烃源岩,以陆源输入为主的混源成因,TOC值平均为2.2%;Ⅲ单元发育Ⅱ_(1)型有机质为主的好—优质烃源岩,以湖泊生物贡献为主,部分为陆源有机质,TOC值平均为4.9%。②始新世强断陷期快速沉降、有限物源供给背景下,暖湿气候-火山活动-深水还原条件协同控制了顺德北凹文二段优质烃源岩的发育。Ⅰ单元沉积期,暖湿气候及火山活动促进了以粒面球藻为主的湖泊藻类勃发,初始生产力高,同时深水还原条件为有机质提供了良好的保存条件,共同控制优质烃源岩的发育和赋存;Ⅱ单元沉积期为暖—凉过渡、半干旱古气候,湖泊藻类数量降低,初始生产力降低,同时陆源输入增加、浅水弱氧化的水体条件使有机质被稀释、分解,烃源岩品质下降;Ⅲ单元沉积期为凉湿的古气候条件,盘星藻和葡萄藻类开始生长,生产力再提升,同时在半深水的还原环境保存条件下,形成了稍次于Ⅰ单元的优质烃源岩。研究结果明确了顺德凹陷不同类型烃源岩的差异成因及发育模式,对边缘凹陷烃源岩精细评价及有利勘探方向选择具有重要的借鉴和指导意义。Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(Ⅰ,Ⅱ,Ⅲ)from bottom to top.Unit Ⅰ features excellent source rocks with Type Ⅰ organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit Ⅱ hosts source rocks dominated by Type Ⅱ_(2) organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit Ⅲ contains good to excellent source rocks dominated by Type Ⅱ_(1) organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit Ⅰ,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit Ⅱ,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water con

关 键 词：珠江口盆地 顺德凹陷 顺德北凹 边缘凹陷 古近系始新统文昌组 古气候 古环境 烃源岩发育模式 

分 类 号：TE122[石油与天然气工程—油气勘探]