西湖凹陷天台斜坡新生代构造差异特征及其形成机制

doi:10.19657/j.geoscience.1000-8527.2022.081

摘要/Abstract

摘要：

天台斜坡位于西湖凹陷西斜坡的南段,经过35年勘探,仅钻探4口井,尚未取得商业油气发现,基础油气地质条件不明确制约了油气勘探进程。针对该斜坡构造特征缺乏系统研究的问题,以三维地震资料精细解释和综合地质分析为基础,系统总结了天台斜坡不同区段的新生代构造样式及其几何学特征和形成机制。天台斜坡自北往南依次表现为双向断层控制的北段复杂斜坡、反向断层控制为主的中段复杂缓坡和顺向断层控制为主的南段简单缓坡。天台斜坡构造特征的区段差异性与其新生代构造演化过程密切相关,从断陷阶段延续到断拗阶段的不均一伸展作用,在其北、中、南段分别控制了不同的断裂发育程度及构造组合样式,并在北段和中段之间形成了特殊的弧形断裂发育带。

关键词: 构造差异, 伸展转换, 弧形断裂, 天台斜坡, 西湖凹陷

Abstract:

The Tiantai slope is located in the southern section of the western slope of the Xihu Sag. After 35 years of exploration, only four wells have been drilled and no commercial discoveries have been made, and the poorly-known geological conditions have restricted the local oil and gas exploration. Based on three-dimensional (3D) seismic data interpretation and comprehensive geological analysis, the Cenozoic tectonic style of the different sections of the Tiantai slope, and its geometrical features and formation mechanism are systematically summarized. From north to south, the Tiantai slope is characterized by a complex slope in the northern section (controlled by two-way faults), a complex gentle slope in the middle section (controlled by antithetic faults), and a simple gentle slope in the southern section (controlled by a synthetic fault). The regional structural differences of the Tiantai slope are closely related to its Cenozoic tectonic evolution. From Paleocene to Eocene, the differential extension may have controlled the different degrees of fault development and structural styles in the northern, middle and southern sections of the Tiantai slope. A special arc-shaped fault development zone may have formed between the northern and middle sections.

Key words: tectonic difference, extensional transformation, arc-shaped fault, Tiantai slope, Xihu Sag

中图分类号:

P618.13

祁鹏, 郭刚, 崔敏, 王欣, 李峰, 李林致. 西湖凹陷天台斜坡新生代构造差异特征及其形成机制[J]. 现代地质, 2023, 37(02): 307-315.

QI Peng, GUO Gang, CUI Min, WANG Xin, LI Feng, LI Linzhi. Cenozoic Tectonic Difference and Its Formation Mechanism of the Tiantai Slope in the Xihu Sag[J]. Geoscience, 2023, 37(02): 307-315.

图/表 7

图1 天台斜坡构造区划及断裂分布图[8]

Fig.1 Map showing the structural branches and fault distributions in the Tiantai slope[8]

图2 天台斜坡北段构造特征(剖面L1,其位置见图1)

Fig.2 Seismic profile showing interpreted structures of the Tiantai slope (northern branch)

图3 天台斜坡中段构造特征(剖面位置见图1) (a)剖面L2;(b)剖面L3

Fig.3 Seismic profile showing interpreted structures of the Tiantai slope(middle branch)

图4 天台斜坡南段构造特征(剖面L4,其位置见图1)

Fig.4 Seismic profile showing interpreted structures of the Tiantai slope (southern branch)

图5 西湖凹陷中部和南部在不同沉积时期的构造活动差异(伸展率采样测线和古落差采样点位置见图1) (a)伸展率分析;(b)主断裂古落差分析

Fig.5 Tectonic activity differences between the middle and southern branch of the Xihu sag

图6 西湖凹陷南部新生代构造演化过程

Fig.6 Summary diagram of Cenozoic tectonic evolution in the southern part of the Xihu sag

图7 西湖凹陷平湖斜坡和天台斜坡古新世—始新世断裂发育过程 (a)古新世—早始新世;(b)中始新世;(c)晚始新世

Fig.7 Schematic diagrams showing the Paleocene-Eocene fault development of the Pinghu and Tiantai slope in the Xihu sag

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