石油勘探与开发2025，Vol.52Issue(2)：306-319,14.DOI:10.11698/PED.20240583
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
摘要
Abstract
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 Ⅱ2 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 Ⅱ1 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 conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit Ⅲ,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit Ⅰ.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.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Key words
Pearl River Mouth Basin/Shunde Sag/Northern Shunde Subsag/marginal sag/Paleogene Eocene Wenchang Formation/palaeoclimate/palaeoenvironment/source rock development model分类
石油、天然气工程引用本文复制引用
裴健翔,金秋月,范代军,雷明珠..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[J].石油勘探与开发,2025,52(2):306-319,14.基金项目
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) （SCKY-2023-HN-3）
