南海北部陆缘大型深水峡谷体系形成机制及充填构型对比研究

Deepwater canyon system is an important sediment routing system for sediments transporting from neritic to abyssal facies. Analysis on depositional filling of deepwater canyons can help to understand for the depositional processes of deepwater systems, and provide plentiful information on evolution of continental marginal dynamics. In this project, three large-scale deepwater canyons (Kaoping canyon, Off Pearl River Mouth canyon, Central canyon) developed in northern continental margins of the South China Sea are taken as our research targets. Depositional architectures of those canyons are described in detail. The genetic relationship between the geomorphic features and depositional fillings, and associated control factors in the different segments of the canyons are discussed. Scour and filling processes and depositional models in different segments of the deepwater canyons are summarized based on the analysis of tectonic movement, sediment supplies, sea-level changes and geomorphic relief. By comparing on those canyons developing in different tectonic and depositional background, difference in the formation evolution and depositional fillings are studied. Sediment transportation and source-to-sink system in different tectonic and depositional background are concluded. The research results will help to deepen the understanding of depositional processes and evolution model of the deepwater systems, and also be helpful for hydrocarbon exploration in the deepwater area in northern continental margins of the South China Sea.

深水峡谷体系是沉积物从浅水向深水搬运的重要通道系统, 因此，深水峡谷体系沉积充填分析既是理解深水沉积作用过程的基础，也能为大陆边缘动力学演变过程研究提供丰富的信息。本项目以南海北部陆缘发育的3条大型深水峡谷体系（高屏峡谷、珠江口外峡谷、西部中央峡谷）为重点解剖对象，通过3条大型峡谷体系的内部构成精细描述，查明不同区带峡谷体系形态-充填-控制因素，结合构造活动、物源供给、海平面升降和微地貌特征分析，重塑各深水峡谷体系侵蚀-充填过程，建立不同区段深水峡谷体系沉积充填模式，进而通过各峡谷体系的对比分析，查明不同构造和沉积背景条件深水峡谷体系形成演化及沉积充填的差异性，建立不同构造和沉积背景条件下深水沉积物输运通道系统，总结不同构造和沉积背景条件下深水区源-汇系统特征。研究成果不仅可以深化深水体系沉积机制及成因演化模式，而且对于南海北部大陆边缘盆地乃至我国广阔的深水海域油气勘探起到重要的推动作用。

基于高精度2D及3D地震资料的最新解释，结合钻井资料及海底调查结果，通过南海北部陆缘3条大型深水峡谷体系(西北部中央峡谷、珠江口外峡谷、东北部高屏峡谷)精细解剖，系统揭示了不同峡谷体系内部构成特征及其差异，指出了西北陆缘中央峡谷为单一下切深、近东西向延伸的峡谷，峡谷位置固定，且具有多段式发育、多物源供给、多阶段充填的特点，而珠江口外峡谷形成与珠江三角洲发育密切相关，垂向上峡谷多期次发育且峡谷位置随时间迁移明显；揭示了南海东北部高屏峡谷体系内部构成特征，查明了台湾-吕宋汇聚大陆边缘沉积物扩散体系演化特征；系统揭示了大型深水峡谷体系形成演化的主控因素，指出了构造活动背景、海平面变化、沉积物供给和古地貌条件是控制了峡谷形成演化的主控因素，其中古地貌条件、沉积物供给是导致峡谷内部充填差异的主因；东北陆缘高屏峡谷形成于俯冲前渊构造带，属于典型构造成因的峡谷体系，珠江口外峡谷发育于现今珠江三角洲的下倾方向，其延伸方向明显受地形影响，而西北陆缘中央峡谷明显受构造和地形双重影响，显然，构造活动与沉积物供给是导致南海北部陆缘3条大型深水峡谷体系发育演化差异的主因。深水峡谷体系是深水区相对粗粒碎屑堆积场所，也是深水区最具潜力的油气储层。研究课题组提出的峡谷内发育以浊积水道砂为优质储层的、成群成带分布的大型岩性圈闭群的新认识，为LS17-2天然气田勘探提供了有力的理论和技术支撑，为该区优质储层预测提供了有效的地质依据。.本项目共发表学术论文15篇，其中SCI 收录论文9篇，中文核心期刊论文5篇。另有2篇论文已投SCI 源刊，目前仍处审稿之中。主办国际学术会议1次，项目组成员参加国际和国内会议12人次（其中7次国际会议）。邀请海外专家来华讲学1人次，项目执行过程中培养毕业博士后1名、博士2名和硕士1名。