石油学报 ›› 2019, Vol. 40 ›› Issue (s1): 139-152.DOI: 10.7623/syxb2019S1012

• 地质勘探 • 上一篇    下一篇

辫状河三角洲沉积特征及成因差异——以珠江口盆地陆丰凹陷恩平组为例

葛家旺1,2, 朱筱敏2, 吴陈冰洁3, 张向涛4, 贾连凯4, 易震4, 肖张波4   

  1. 1. 西南石油大学地球科学与技术学院 四川成都 610500;
    2. 中国石油大学(北京)地球科学学院 北京 102249;
    3. 中国石化集团新星石油有限责任公司新能源研究院 北京 100083;
    4. 中海石油(中国)深圳分公司研究院 广东深圳 518067
  • 收稿日期:2018-08-01 修回日期:2018-12-05 出版日期:2019-07-25 发布日期:2019-07-15
  • 通讯作者: 朱筱敏,男,1960年6月生,1982年获华东石油学院勘探系石油地质专业学士学位,1990年获石油大学矿产普查与勘探专业博士学位,现为中国石油大学(北京)教授、博士生导师,主要从事层序地层学和储层沉积学方面的教学和科研工作。Email:xmzhu@cup.edu.cn
  • 作者简介:葛家旺,男,1988年10月生,2011年获中国地质大学(武汉)学士学位,2018年获中国石油大学(北京)博士学位,现为西南石油大学地球科学与技术学院讲师,主要从事层序地层学和沉积学方面的研究。Email:gjwddn@163.com
  • 基金资助:

    国家科技重大专项(2016ZX05001-002)和西南石油大学科研"起航计划"项目(2018QHZ010)资助。

Sedimentary characteristics and genetic difference of braided delta: a case study of Enping Formation in Lufeng sag, Pearl River Mouth Basin

Ge Jiawang1,2, Zhu Xiaomin2, Wu Chenbingjie3, Zhang Xiangtao4, Jia Liankai4, Yi Zhen4, Xiao Zhangbo4   

  1. 1. School of Geosciences and Technology, Southwest Petroleum University, Sichuan Chengdu 610500, China;
    2. College of Geosciences, China University of Petroleum, Beijing 102249, China;
    3. New Energy Research Institute, Sinopec Star Petroleum Co. Ltd., Beijing 100083, China;
    4. Research Institute of Shenzhen Branch of CNOOC China Limited, Guangdong Shenzhen 518067, China
  • Received:2018-08-01 Revised:2018-12-05 Online:2019-07-25 Published:2019-07-15

摘要:

基于岩心、测井和三维地震资料,研究了珠江口盆地陆丰凹陷始新统恩平组辫状河三角洲类型、沉积特征和演化规律。钻井、测井曲线和地震反射终止关系研究表明,陆丰凹陷恩平组可划分为4个三级层序(自下而上分别为ESQ1、ESQ2、ESQ3和ESQ4),发育了S型前积、斜交前积、叠瓦前积和隐性前积4类辫状河三角洲体系,其具体特征如下:①S型前积型三角洲具有典型的顶积层、前积层和底积层三层结构,岩性以粗砂岩-细砂岩为主,含砂率为35%~65%,地震地貌响应表现为面积小于100 km2的朵叶状,主要发育于ESQ1和ESQ2时期;②斜交前积型三角洲仅包括前积层和底积层两层结构,岩性以砾岩和粗砂岩为主(偶含火山碎屑岩),含砂率为55%~75%,在地震地貌上表现为伸长状的朵叶体,面积可达200 km2,发育于ESQ1和ESQ2时期;③叠瓦前积型三角洲在地震剖面显示为低角度的叠瓦前积反射结构,岩性以粗砂岩为主,含砂率为50%~72%,地震地貌响应为面积大的朵状和树枝状(面积为250~700 km2),主要分布于ESQ3层序;④隐性前积型三角洲在地震剖面上表现为亚平行结构或不明显的叠瓦状前积,岩性为中-细砂岩夹薄层的煤层或杂色泥岩,含砂率为30%~58%,地震地貌以振幅分带的河道状为特征,展布面积可达900 km2,仅识别于ESQ4层序。从S型前积到隐性前积三角洲,湖盆水体逐渐变浅(由120~180 m到10~30 m),可容纳空间与沉积物供给比值(A/S)逐步趋近于0。研究区发育的4种类型的三角洲地震反射结构、沉积特征和地震地貌响应变化,是湖盆由鼎盛到消亡演变过程中水体变化和A/S比值的综合反映。该研究成果为陆相湖盆三角洲的沉积特征和分布演化提供了新的实例,也可为其他湖盆三角洲研究提供类比和参考。

关键词: 珠江口盆地, 陆丰凹陷, 恩平组, 辫状河三角洲, 沉积特征, 地震地貌

Abstract:

Based on a comprehensive analysis of core, well logging and 3D seismic data, this paper studies sedimentary characteristics and evolution of the braided delta of the Eocene Enping Formation in Lufeng sag of Pearl River Mouth Basin. The relationship between bovehole log and seismic reflection termination shows that Enping Formation can be divided into four third-order sequences (ESQ1, ESQ2, ESQ3 and ESQ4 from bottom to top), where the braided delta system is developed as S-shaped foreset, oblique foreset, imbricated foreset and concealed foreset structures. The specific characteristics are as follows:(1) the S-type foreset has a typical three-layer configuration, including topset bed, foreset bed and bottom-set bed. The lithology is dominated by coarse-grained to fine-grained sandstone with the sandstone ratio of about 35% -65%, and the seismic geomorphological response presents a lobe-like shape with an area less than 100 km2. It is mainly developed in ESQ1 and ESQ2. (2) The oblique foreset delta only consists of two layers (foreset bed and bottom-set bed), and the lithology is dominated by conglomerate and coarse-grained sandstone (occasionally with volcanic clastic rocks) with the sandstone ratio of about 55% -75%. It is shown as an elongate and lobate geometry on the seismic geomorphologic map, with an area up to 200 km2, mainly developed during the ESQ1 and ESQ2 periods. (3) The imbricated foreset delta has a low-angle progradated foreset reflection; the lithology is dominated by coarse-grained sandstones with the sandstone ratio of about 50% -72%; the seismic geomorphological response displays a dendritic and lobate geometry, covering an area of 250-700 km2. It is mainly distributed in the ESQ3 period. (4) Concealed foreset delta appears as a sub-parallel structure or an inconspicuous progradated foreset; the lithology is dominated by meso-fine-grained sandstone, mixed with coal and vegetated mudstones, and the sandstone ratio is 30% -58%; the seismic geomorphology is characterized by river channels zoned according to amplitudes, covering an area up to 900 km2; it can only be detected in ESQ4 sequence. It is suggested that the depth of lake water gradually becomes shallower (from 120-180 m to 10-30 m), in response to the evolution from S-shape foreset to concealed foreset, and the ratio of accommodation space versus sediment supply (A/S) is gradually approaching to 0. The four types of deltaic seismic reflection structure, sedimentary characteristics and the changing seismic geomorphological response in the study area are a comprehensive reflection of water mass change and A/S ratios of the lake basin evolved from the peak development to extinction. This study may provide a new example for the sedimentary characteristics and distribution evolution of continental braided delta, which could provide analogies and references for exploring other lake basin delta.

Key words: Pearl River Mouth Basin, Lufeng sag, Enping Formation, braided delta, sedimentary characteristics, seismic geomorphology

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