南海北部宽缓大陆架海平面变化及双坡折带层序地层模型

South China Sea is one of the largest Cenozoic marginal seas in the western Pacific ocean, having a wide and low-gradient shelf and simultaneously developing two slope break belts in the north, which are inner shelf depositional slope break and shelf-margin slope break. Affected by sea level changes, depositional type, depositional mode and sequence stratigraphic model of the two types of slope break belt are obviously different. This project research focuses on the dual slope break belts of the wide and low-gradient shelf in the north of South China Sea, stratigraphic architecture and stacking styles are identified on the basis of single well sedimentary facies analysis and well sedimentary facies correlation, chronostratigraphic framework is established according to micro-paleontological analysis and coast onlap is tracked on seismic profile, consequently,geological knowledge-base of sea level changes is created so as to set up geological model of sea-level changes process, combined with geochemical profile analysis. various influences of rate and amplitude of different sea-level change on depositional type and depositional mode of each slope break belt are analyzed to determine the relationship of deposit response controlled by sea level changes of the slope break belts and the sequence stratigraphic division scenario, and to construct high resolution isochronous stratigraphic division and correlation framework, combining with the analysis of provenance, characteristics of sedimentary supply in different time units and seismic sedimentology analysis to make the types, assemblages and distribution of depositional systems clear, and then build the composite model of sequence stratigraphy of the dual slope break belts in the wide and low-gradient shelf. The above research, from the perspective of sedimentology and sequence stratigraphy, will lay a solid foundation for accurately predicting the favorable zones of oil and gas exploration, as well as supplement and improve the sequence stratigraphic theory model of single slope break belt.

南海是新生代西太平洋最大边缘海之一，其北部具有宽缓大陆架，同时发育两个坡折带，即陆架内沉积坡折和陆架边缘坡折。受海平面变化的影响，两个坡折带的沉积类型、沉积方式及层序模式存在差异。本项目以南海北部宽缓陆架双坡折带为研究对象，通过单井沉积相分析及连井对比确定地层构型及堆积叠加样式，微体古生物分析建立年代地层框架，追踪地震海岸上超，结合地球化学剖面分析，建立海平面变化地质知识库，构建海平面变化过程地质模型；分析不同海平面变化速率及变化幅度分别对各坡折带沉积类型及沉积方式的影响，确定坡折带海平面变化沉积响应关系，以及层序地层划分方案，建立高精度等时地层划分对比格架；结合不同时间单元沉积物源及沉积供应特点分析，以及地震沉积学分析，确定沉积体系类型、组合及其分布，建立宽缓陆架双坡折带层序地层复合模型。从沉积及层序角度，为准确预测有利油气勘探区带奠定扎实的基础。同时补充完善单坡折层序地层理论模式。

南海是新生代西太平洋最大边缘海之一，其北部宽缓大陆架发育陆架内沉积坡折，而陆架边缘发育陆架边缘地貌坡折。本项目以南海北部宽缓陆架双坡折带为研究对象，首先，通过地震上超点、地层厚度变化、沉积相变化关系及古生物资料分析，对两种类型的坡折带进行识别，并总结不同类型破折带的基本特点，以及坡折带随时间的横向迁移特征；其次，通过单井沉积相分析及连井对比确定地层构型及堆积叠加样式，以及微体古生物分析建立年代地层框架，追踪地震海岸上超，结合地球化学剖面分析，建立海平面变化地质知识库，构建海平面变化过程地质模型，确定适合于海平面变化分析的方法体系及分析步骤；第三，通过分析不同海平面变化速率及变化幅度分别对各坡折带沉积类型及沉积方式的影响，确定坡折带海平面变化沉积响应关系，以及层序地层划分方案，建立高精度等时地层划分对比格架；第四，结合不同时间单元沉积物源及沉积供应特点分析，以及地震沉积学分析，确定沉积体系类型、组合及其分布，建立宽缓陆架双坡折带层序地层复合模型。总之，本研究从南海海平面变化对沉积及层序控制角度出发，通过不同坡折带层序发育模型的构建，进而对确定等时层序地层格架内烃源岩、储层及盖层发育规律，为准确预测有利油气勘探区带奠定扎实的基础。同时补充完善单坡折层序地层理论模式。