天文周期约束下始新统湖相地层页岩岩相组合类型及其发育模式——以北部湾盆地涠西南凹陷流沙港组为例  

Shale lithofacies association types and development models in Eocene lacustrine facies strata constrained by astronomical cycles:A case study of the Liushagang Formation in the Weixinan sag,Beibuwan Basin

作　　者：李国萃 石巨业 樊太亮[1] 胡德胜 游君君 李一凡[1] 高志前[1] 邓成昆 范家豪 周刚 LI Guocui;SHI Juye;FAN Tailiang;HU Desheng;YOU Junjun;LI Yifan;GAO Zhiqian;DENG Chengkun;FAN Jiahao;ZHOU Gang(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083;China National Offshore Oil Corporation,Zhanjiang Branch,Zhanjiang 524034,Guangdong)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中海石油(中国)有限公司湛江分公司,广东湛江524034

出　　处：《第四纪研究》2023年第6期1614-1629,共16页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:42102150)资助。

摘　　要：北部湾盆地涠西南凹陷油藏储量丰富。其中,始新统流沙港组发育主力烃源岩层系,以湖相泥页岩沉积为主,沉积厚度较大,具有较高的稳定性与连续性。对流沙港组进行旋回地层学及岩相组合的研究可为盆地内勘探新区页岩油甜点精细预测与评价提供重要指导。本研究以涠西南凹陷始新统流沙港组为例,以GR测井曲线为替代性指标,对其进行数据预处理、频谱分析、滤波和调谐分析,识别了研究区多口井的天文周期,以长、短偏心率、斜率及岁差周期(405 ka、100 ka、40 ka和20 ka)作为四、五、六、七级层序划分参考曲线,将流沙港组三段上亚段至流沙港组二段下亚段(简称流三上-流二下)划分为14个四级层序,44个五级层序,建立了研究区高精度等时地层格架。基于有机质丰度、矿物组成特征等,将流三上-流二下页岩划分为九类13种岩相类型,并依据岩芯、岩相及曲线变化特征,以五级层序为单元,划分出A型、B型和C型3种岩相组合类型,分析了不同岩相组合的特征和沉积环境,建立了天文周期约束下湖相页岩岩相组合发育模式。结果显示,流三上亚段水体较浅,陡坡带、缓坡带及二号断裂中央隆起区岩相组合主要为A型;深湖-半深湖区以C型和B型为主。流二下亚段水体较深,仅在滨岸带发育A型,二号断裂中央隆起区主要发育B型,半深湖-滨浅湖区发育B型和C型,深湖区均为C型。研究成果不仅为涠西南凹陷页岩油甜点精细预测提供了有力支撑,也为其他陆相盆地页岩岩相组合发育模式提供了参考模板,对页岩油的勘探开发具有重要意义。The Weixinan depression in the Beibu Gulf Basin has abundant oil reserves.Among them,the Eocene Liushagang Formation developed the main hydrocarbon source rock series,mainly composed of lacustrine mud shale deposits,with a high sedimentary thickness,which has high stability and continuity.The study on the cyclic stratigraphy and lithofacies association of the Liushagang Formation can provide important guidance for the fine prediction and evaluation of shale oil sweet spots in the exploration area of the basin.This article takes the Eocene Liushagang Formation in the Weixinan sag as an example,and uses GR log curve as an alternate index,data preprocessing,spectrum analysis,filtering and tuning analysis are performed on it,the astronomical period of multiple wells in the study area is identified,and long,short eccentricity,slope and precessional period(405 ka,100 ka,40 ka and 20 ka)are used as reference curves for four,five,six and seven sequence divisions.The high-precision isochronous stratigraphic framework in the study area was established by dividing the upper submember of Section 3 of Liushagang Formation to the lower submember of Section 2 of Liushagang Formation into 14 fourth order Quaternary sequences and 44 fifth order Quaternary sequences.Based on the abundance of organic matter,mineral composition and so on,the lithofacies of the upper submember of Section 3 of Liushagang Formation to the lower submember of Section 2 of Liushagang Formation are divided into 9 categories and 13 types.According to the change characteristics of core,lithofacies and curve,three lithofacies assemblages of A type,B type and C type are divided into three lithofacies assemblages based on the five-order sequence as the unit,and the characteristics and sedimentary environment of different lithofacies assemblages are analyzed.The development model of lacustrine shale facies association constrained by astronomical period is established.The results show that the water body in the upper submember of Section 3 of Liushagang Formation

关 键 词：旋回地层学 天文周期 湖相页岩 岩相组合 流沙港组 

分 类 号：P534.613[天文地球—古生物学与地层学] P539.2[天文地球—地质学] P512.6