东海盆地西湖凹陷平湖斜坡带平北区始新统宝石组沉积环境及沉积相类型

蒋一鸣; 赵洪; 唐贤君; 姜雪; 徐振中

doi:10.11781/sysydz2025050941

东海盆地西湖凹陷平湖斜坡带平北区始新统宝石组沉积环境及沉积相类型

doi: 10.11781/sysydz2025050941

中海石油(中国)有限公司上海分公司, 上海 200335

基金项目:

国家自然科学基金项目 42430806

中海石油(中国)有限公司上海分公司生产性科研项目 SCKY-2024-YJY07

中海石油(中国)有限公司重大科技专项 KJZX-2023-0101

详细信息

作者简介:
蒋一鸣(1983—)，男，高级工程师，从事石油地质研究。E-mail: jiangym2@cnooc.com.cn

中图分类号: TE121.3
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出版历程
- 收稿日期: 2024-02-24
- 修回日期: 2025-08-05
- 刊出日期: 2025-09-28

Sedimentary environment and facies types of Eocene Baoshi Formation in Pingbei area, Pinghu slope belt, Xihu Sag, East China Sea Basin

Shanghai Branch, CNOOC China Limited, Shanghai 200335, China

摘要

摘要: 东海盆地西湖凹陷平湖斜坡带平北区始新统宝石组沉积环境与沉积相认识不清，制约了对该区宝石组储层与烃源岩的评价，阻碍了油气勘探进程。在对宝石组地层重新厘定的基础上，综合运用古生物学、微量元素分析、岩心观察、粒度分析与测井相分析等方法，对研究区9口井的宝石组沉积环境和沉积相进行了系统研究，明确了宝石组沉积相类型。研究表明，平北区宝石组藻类和孢粉含量低，孢粉以喜湿蕨类孢子为主，沟鞭藻、钙质超微化石和有孔虫等海相化石含量较少，表明宝石组沉积时期为半咸水的海陆过渡相，以温暖、湿润气候为主。Sr、Ba、Ni和V等元素的综合分析表明，宝石组沉积时期为弱还原的贫氧环境；相对于天台斜坡带，平北区淡水陆相化石相对较多，为相对局限的海陆交互沉积环境。研究区不同的构造带沉积环境与沉积相有所差异：孔雀亭构造带宝石组主要发育三角洲沉积相，主要发育水下分流河道、河口坝及水下分流间湾微相，席状砂发育较少；宝云亭与武云亭构造带宝石组沉积于受局部海水影响的沉积环境，发育潮坪相，主要发育潮间带砂体，潮间带主要发育潮道、砂坪、混合坪及泥坪沉积微相；在西部斜坡带南部的天台斜坡带发育大套厚层泥岩，代表局限海沉积，其分布范围较小。
- 沉积相 /
- 沉积环境 /
- 平北区 /
- 平湖斜坡带 /
- 宝石组 /
- 西湖凹陷 /
- 东海盆地
Abstract: The unclear understanding of the sedimentary environment and facies of the Baoshi Formation in the Pingbei area of the Pinghu slope belt, Xihu Sag, East China Sea Basin, has restricted the evaluation of the Baoshi Formation reservoirs and source rocks in this area, and hindered the progress in oil and gas exploration. Based on the redefinition of the Baoshi Formation strata, a systematic study of the sedimentary environment and facies of the Baoshi Formation from nine wells in the study area was conducted by integrating paleontology, trace element analysis, core observation, grain size analysis, and logging facies analysis. The types of sedimentary facies in the Baoshi Formation were clarified. The results showed that the Baoshi Formation in the Pingbei area had low contents of algae and palynomorphs, with hygrophilous fern spores being dominant. A small number of dinoflagellates, calcareous nannofossils, and foraminifera were present. These features indicated that during the deposition of the Baoshi Formation, the environment was a brackish marine-continental transitional setting under predominantly warm and humid climatic conditions. Comprehensive analysis of Sr, Ba, Ni, and V indicated that the Baoshi Formation was deposited under a weakly reducing, suboxic environment. Compared with the Tiantai slope belt, more freshwater terrestrial fossils were found in the Pingbei area, suggesting a relatively restricted transitional sedimentary environment between land and sea. The sedimentary environment and facies varied across different structural zones in the study area. In the Kongqueting structural zone, the Baoshi Formation was mainly characterized by deltaic sedimentary facies, primarily consisting of underwater distributary channels, mouth bars, and interdistributary bay microfacies, with limited development of sheet sand bodies. In the Baoyunting and Wuyunting structural zones, the Baoshi Formation was deposited in an environment influenced by local seawater, where tidal flat facies and intertidal sand bodies were developed. The intertidal zone mainly contained tidal channels, sand flats, mixed flats, and mud flats as depositional microfacies. In the southern part of the western slope belt, the Tiantai slope belt developed thick mudstone layers, suggesting restricted marine deposition with a relatively limited spatial distribution.
- sedimentary facies /
- sedimentary environment /
- Pingbei area /
- Pinghu slope belt /
- Baoshi Formation /
- Xihu Sag /
- East China Sea Basin
注释:

利益冲突声明/Conflict of Interests

所有作者声明不存在利益冲突。

All authors declare no relevant conflict of interests.

作者贡献/Authors’Contributions

蒋一鸣完成的文章整体构思，关键技术分析及写作；赵洪完成的沉积相研究及论文写作；唐贤君、徐振中完成的古生物特征分析及写作；姜雪完成的图件及论文修改。所有作者均阅读并同意最终稿件的提交。

JIANG Yiming contributed to the overall conceptual framework, key technical analyses, and manuscript writing. ZHAO Hong conducted the sedimentary facies research and wrote the manuscript. TANG Xianjun and XU Zhenzhong performed the paleontological analyses and wrote the manuscript. JIANG Xue prepared the figures and revised the manuscript. All authors have read the final version of the paper and consented to its submission.

HTML全文

图 1 东海盆地西湖凹陷研究区构造概况(a、b)及地层综合柱状图(c)

Figure 1. Structural overview (a, b) and comprehensive stratigraphic column (c) of study area in Xihu Sag, East China Sea Basin

下载: 全尺寸图片幻灯片

图 2 东海盆地西湖凹陷平湖斜坡带平北区典型井宝石组孢粉和藻类

a.Ulmipollenites minor，A7井，4 125 m；b-d.Abietineae/Pinuspollenites spp.，A7井，4 125 m；e.Taxodiaceaepollenites hiatus，A7井，4 115 m；f.Operculodinium centrocarpum，A7井，4 115 m；g.Pediastrum sp.，A7井，4 115 m；h.Lych-nothamnus vectensis，A2井，4 115 m，顶视图；i.Lychnothamnus vectensis，A2井，4 115 m，侧视图。

Figure 2. Palynomorphs and algae from Baoshi Formation in typical wells of Pingbei area, Pinghu slope belt, Xihu Sag, East China Sea Basin

下载: 全尺寸图片幻灯片

图 3 东海盆地西湖凹陷平湖斜坡带平北区始新统宝石组微量元素特征

Figure 3. Trace element characteristics of Eocene Baoshi Formation in Pingbei area, Pinghu slope belt, Xihu Sag, East China Sea Basin

下载: 全尺寸图片幻灯片

图 4 东海盆地西湖凹陷西部斜坡带始新统宝石组岩心特征

a.A3井，4 190 m，水下分流河道泥砾；b.A2井，4 111.5 m，水下分流河道，冲刷面；c.A2井，4 051.5 m，河口坝波状层理；d.A2井，4 109.89 m，河口坝反韵律；e.A2井，4 107.62 m河口坝泄水构造；f.A2井，4 053 m，河口坝变形层理；g.A4井，4 059 m潮道双向交错层理；h.A4井，4 059 m，砂坪交错层理；i.A8井，3 324.3 m，混合坪爬升层理；j.A10井，3 631.9 m，局限海生物遗迹。

Figure 4. Core characteristics of Eocene Baoshi Formation in western slope belt, Xihu Sag, East China Sea Basin

下载: 全尺寸图片幻灯片

图 5 东海盆地西湖凹陷孔雀亭构造带始新统宝石组典型井砂岩概率累计曲线特征

a.A2井，4 112 m，水下分流河道；b.A2井，4 106.89 m，河口坝；c.A5井，4 059 m，潮道；d.A8井，3 630.7 m，砂坪—混合坪。

Figure 5. Characteristics of sandstone probability cumulative curves from typical wells in Eocene Baoshi Formation, Kongqueting structural zone, Xihu Sag, East China Sea Basin

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图 6 东海盆地西湖凹陷典型井始新统宝石组沉积相连井剖面

Figure 6. Connecting well profiles of sedimentary facies in Eocene Baoshi Formation from typical wells in Xihu Sag, East China Sea Basin

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表 1 东海盆地西湖凹陷不同地区始新统宝石组微体古生物特征对比

Table 1. Comparison of microfossil characteristics in Eocene Baoshi Formation between different areas of Xihu Sag, East China Sea Basin

构造区带		平湖斜坡带平北区			天台斜坡带
构造区带		宝云亭构造带	武云亭构造带	孔雀亭构造带	天台斜坡带
微体古生物	孢粉	类似特征：杉科繁盛，松科和榆科花粉发育，金缕梅科、桦木科、壳斗科花粉以及水龙骨科孢子也有一定含量，可称为杉粉Taxodiaceaepollenites—双束松粉Pinuspollenites—榆粉Ulmipollenites—栎粉Quercoidites组合
	孢粉	孢粉化石丰度和分异度均较高	孢粉化石丰度较高，但类型单调，裸子花粉占绝对优势	孢粉化石丰度和分异度较高	孢粉化石丰度和分异度均较高
	沟鞭藻及其他藻类	沟鞭藻贫乏, 淡水藻类化石相对较丰富，以盘星藻为主	未见沟鞭藻，仅见淡水绿藻，类型单调	未见沟鞭藻，仅见淡水绿藻，类型单调，数量少	发现少量绿藻类的盘星藻、疑源类、沟鞭藻，化石丰度和分异度不高
	钙质超微化石	少量发现	少量发现	未发现	在多个深度段发现个别钙质超微化石
	有孔虫	少量发现	少量发现	未发现	在多个层位见数量不等的有孔虫
沉积环境指示		局限的海陆交互的沉积环境，淡水陆相化石相对较多			相对开放的滨海环境，海相及陆相化石共存

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