海洋地质与环境重点实验室知识库

莺歌海盆地是我国海上油气勘探开发的热点区，天然气资源丰富，且探明程度不高，勘探开发潜力巨大。由于盆地覆盖了巨厚的新生界沉积，目前对于盆地的各类地质构造，尤其是深部构造的了解还不够全面，这一定程度上影响了盆地油气资源的评估和油气藏的精确探查。

本研究基于卫星测高重力异常，利用位场数据处理和反演技术，系统地研究盆地内的断裂构造及其特征，分析断裂与构造单元、油气相关构造之间的耦合关系。论文的主要工作和成果如下：

（1）利用归一化总水平导数垂向导数（NVDR-THDR）和最小曲率位场分离方法系统地识别了莺歌海盆地及邻区的断裂，分析了断裂的分布特征。与前人成果相比，本次识别的断裂体系更加清晰完善，揭示了红河断裂带在中央坳陷的延伸——中央断裂，并利用2D地震剖面进行了证实。此外，识别了中央坳陷内部的NWW向断裂和莺东斜坡附近的NEE向、NNE向断裂。

（2）采用Globsed V3沉积层模型数据作为约束，利用双界面模型重力场快速正反演方法，计算了莺歌海盆地的新生界沉积厚度。在此基础上，结合断裂分布和剩余布格重力异常，对莺歌海盆地的构造单元进行了划分。结合前人研究成果，对已知的构造单元边界进行了调整，同时新识别了三个构造单元：乐东南洼陷和中建西洼陷（中央断裂围限的两个局部拉分盆地）、昌南构造（东方区和乐东区之间的构造转换带）。

（3）分析了深大断裂和盆地沉积中心的耦合关系。紧邻中央断裂以西多个沉积中心呈NNW-SSE向排列，以东为沉积厚度变小的梯度带。中央断裂的左行左阶断层系围限了局部拉分盆地，其中乐东南洼陷为一个沉积层厚度大于15 km的沉积中心。上述现象表明中央断裂控制了莺歌海盆地的沉积作用。

（4）分析了深大断裂与底辟构造的耦合关系。中央坳陷的底辟构造主要分布于中央断裂以西，同时具有紧邻断裂发育的特点，乐东区底辟被中央断裂分隔为3个底辟带。上述现象表明中央坳陷底辟构造的发育受控于中央断裂。

本文的研究成果有利于深化对莺歌海盆地的地质认识，为油气勘探和基础地质研究提供更多的地球物理依据。

The Yinggehai Basin is a significant area for offshore oil and gas exploration and development in China, known for its substantial natural gas reserves. Despite this, the exploration level remains relatively low, indicating considerable potential for further exploration and development. The basin's thick Cenozoic sedimentary cover hinders a comprehensive understanding of its geological structures, particularly at greater depths. This limitation affects the accurate assessment of hydrocarbon resources and the precise identification of oil and gas reservoirs.

This study utilized satellite altimetry gravity anomaly, combined with potential field data processing and inversion techniques, to systematically investigate the fault structures and their characteristics within the basin. It also analyzed the interactions between faults, structural units, and hydrocarbon-related structures. The primary work and key findings are as follows:

By employing the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) and the minimum curvature field separation method, we systematically identified faults in the Yinggehai Basin and its adjacent areas, and analyzed their distribution patterns. This research delineates a more defined and comprehensive fault system compared to prior studies. The presence of the Central Fault (CF), a branch of the Red River Fault Zone within the Central Depression, was confirmed using 2D seismic profiles. Additionally, newly discovered faults within the Central Depression, trending NWW, and near the Yingdong slope, trending NEE and NNE, were identified.

Using the Globsed V3 sediment thickness model as a constraint, we applied the rapid forward and inversion method of the gravity field in a dual-interface model to calculate the thickness of the Cenozoic sedimentary layer in the Yinggehai Basin. By combining the distribution of faults and the residual Bouguer gravity anomaly, we were able to delineate the basin's structural elements. Integrating previous research findings, we adjusted the boundaries of known structural elements and identified three new structural elements: the Ledongnan Sub-sag and the Zhongjianxi Sub-sag (two local pull-apart basins bounded by the central fault), and the Changnan Structure (a structural transition zone between the Dongfang and Ledong areas).

We analyzed the relationship between deep faults and depocenters. West of the CF, several depocenters align in an NNW-SSE direction, while to the east, there is a gradient zone with decreasing sediment thickness. The left-stepping sinistral fault system of the CF confines the local pull-apart basins, with the Ledongnan Sub-sag being a depocenter where the sediment thickness exceeds 15 km. This highlights the CF's significant role in sedimentation patterns.

Furthermore, we explored the interconnection between deep faults and diapirs. Diapirs in the Central Depression are mainly distributed to the west of the CF and develop in close proximity to the fault. In the Ledong area, diapirs are segmented into three zones by the CF, indicating that their development in the Central Depression is controlled by the CF.

The findings of this study enhance the geological understanding of the Yinggehai Basin, providing robust geophysical support for oil and gas exploration as well as fundamental geological research.

第1章 绪论  1

1.1 选题背景和研究意义    1

1.1.1 选题背景     1

1.1.2 研究意义     3

1.2 研究现状和存在问题    3

1.2.1 莺歌海盆地断裂研究现状  3

1.2.2 莺歌海盆地构造单元研究现状  7

1.2.3 莺歌海盆地底辟构造研究现状  9

1.2.4 存在的主要问题  11

1.3 研究内容与方法    11

1.3.1 研究内容     11

1.3.2 研究方法     12

1.3.3 技术路线     12

1.4 论文主要工作量和创新点    13

1.4.1 主要工作量  13

1.4.2 主要创新点  14

第2章 区域地质概况  15

2.1 大地构造背景 15

2.1.1 红河断裂带走滑运动  15

2.1.2 南海演化     17

2.2 盆地演化与地层划分    18

2.3 地层密度特征 19

2.4 邻区盆地概况 20

2.4.1 北部湾盆地  20

2.4.2 琼东南盆地  20

第3章 莺歌海盆地及邻区断裂分布特征  21

3.1 重力异常特征 21

3.2 重力资料识别断裂构造的方法    23

3.2.1 位场边缘识别方法     23

3.2.2 位场分离方法     24

3.3 断裂识别结果 25

3.4 断裂分布特征 27

3.4.1 与前人识别断裂对比  27

3.4.2 一级断裂特征     29

3.4.3 二级断裂特征     34

3.4.4 三级断裂特征     36

3.5 红河断裂在中央坳陷的延伸特征 38

3.6 莺歌海盆地NE走向断裂的意义  41

第4章 莺歌海盆地构造单元分布特征     42

4.1 新生界沉积层厚度 42

4.2 莺歌海盆地构造单元分布    44

4.2.1 构造单元划分原则     44

4.2.2 构造单元划分方案     45

4.2.3 构造单元分布特征     47

第5章 莺歌海盆地深大断裂的地质意义  50

5.1 深大断裂对沉积中心的控制作用 50

5.2 深大断裂对底辟构造发育的控制作用 51

5.3 深大断裂与莺东斜坡乐东鼻状凸起的关系 53

第6章 结论与建议     54

6.1 结论 54

6.2 建议 54

参考文献       55

致谢       65

作者简历及攻读学位期间发表的学术论文与其他相关学术成果    67