构造-沉积耦合过程的数值模拟:以南海北部阳江凹陷为例

Numerical modeling of the coupling between strike-slip faulting and sedimentation: A case from the Yangjiang Sag of northern South China Sea

以构造变形为核心的内动力过程和以沉积"源–汇"过程为核心的外动力过程,如何动态塑造盆地精细地貌景观,是油气精准勘探必须突破的关键技术。本研究以南海北部陆缘珠江口盆地的阳江凹陷为例,试图探索NW向阳江–一统暗沙深大断裂带对周缘新生代沉降中心分布的控制作用。为此,本文采用Badlands沉积数值模拟方法,定量分析阳江–一统暗沙断裂带的运动学特征,模拟阳江凹陷新生代地层构造-沉积耦合过程。模拟结果显示,阳江–一统暗沙断裂带在始新世末期是一条左行走滑断裂带,其走滑过程主要可分为两个阶段。其中,在早期慢走滑阶段,走滑位移量约800 m,沿断裂带走滑方向,恩平19洼的沉降中心发生迁移;在后期快走滑阶段,走滑位移量约1 200 m,模拟剖面可识别出明显的花状构造,恩平19洼的沉降中心加速向北迁移,并发生逆时针旋转。

To dynamically shape the fine geomorphic landscape of a basin is a key technology required in efficient oil and gas exploration. In this paper, the Yangjiang Sag in the Pearl River Mouth Basin on the northern margin of the South China Sea is selected as a case to explore the NW-trending Yangjiang-Yitong’ansha Blind Fault Zone(YYBFZ) and its control over the distribution patterns of Cenozoic depocenters in its periphery. Badlands ’ numerical sedimentation simulation is used to quantitatively analyze the kinematic characteristics of the YYBFZ for further understanding the Cenozoic tectono-sedimentary coupling process of the Yangjiang Sag. The simulation results suggest that the YYBFZ was a sinistral strike-slip fault zone formed by the end of Eocene, and the strike slip process can be divided into two stages. The early stage is a slow strike slip stage, with a strike-slip displacement of about 800 m, and the depocenters of the Enping 19 Subsag migrate along the slip direction of the fault;In the late stage, however, the slip was fast and the displacement of the strike slip may reach the figure about 1 200 m, and along the simulation section, obvious flower-like structures are observed. At the same time, the depocenters of the Enping 19 Subsag accelerated its move northward with rotation anticlockwise.