金湖凹陷断裂特征及其石油地质意义

金湖凹陷自晚白垩世-新生代发育复杂断裂系统,在统一应力场的作用下凹陷内形成伸展断裂、走滑断裂和挤压断裂。断裂系统的演化分为初始伸展、继承伸展、强烈伸展和走滑叠加四个阶段。初始伸展阶段凹陷伸展作用较弱,除主边界断层外,其他断层对沉积地层控制作用较弱;继承伸展阶段,凹陷持续伸展,部分早期断层停止活动;强烈伸展阶段,构造活动集中于主断层之上,形成主要沉积凹陷;走滑叠加阶段,凹陷内断层发生右旋走滑作用,在伸展构造之上叠加了走滑构造,该构造运动奠定了金湖凹陷现今的构造格局。杨村断层和石港断层为受基底断层控制的持续活动断层,而铜城断层是晚期形成调节石港断层和杨村断层走滑应力的变换断层。断裂活动受区域应力场和基底先存断裂的共同控制,表现为两期构造的叠加。两期构造运动控制了金湖凹陷油气的形成、运移和聚集。

Structural Features of the Jinhu Sag in the Subei Basin and its Petroleum Geological Significance

From Late Cretaceous to Cenozoic, the Jinhu sag (south-west part of the Subei Basin) developed a complex fault system. The fault system includes extensional faults,strike-slip faults and reverse faults which were controlled by the unified regional stress field. The Fault system experienced four stages of evolution:initial extension, inheritance extension, intense extension, and superimposed strike-slip stages. The sag extended weakly in the initial extension stage and the faults had weakly controls on sedimentation except the major fault. In the inheritance extension stage, the basin experienced continual extension; some of the earlier faults were inactive. The major faults such as the Shigang fault and Yangcun fault strongly active and formed the main sags in the intense extension stage. The faults experienced dextral strike slipping and extension in superimposed strike-slip stage. And consequently, the structural pattern of the Jinhu sag was established. The Yangcun and Shigang faults are persistence active faults controlled by the pre-existing basement faults. The Tongcheng fault, a transfer fault which accommodated the strike-slip stress between the Shigang and Yancun faults, was formed in the late stage. The activity of fault system was mainly controlled by the pre-existing faults and region stress filed. Under the influence of the two stage tectonic movements, the Jinhu sag formed the hydrocarbon traps.