渤中凹陷石南一号断层分段和演化特征及其油气成藏控制作用

Segmentation and evolution characteristics of Shinan No.1fault in Bozhong Sag and its control on hydrocarbon accumulation

石南一号断层是渤海海域渤中凹陷北部一条十分重要的控凹、控藏断层,弄清其静态构造特征及动态演化规律,对指导油气精细勘探具有重要意义。利用现有勘探资料,系统刻画了石南一号断层的构造特征,剖析了其形成演化过程及成因机制,并分析了其对油气成藏的控制作用。研究认为:石南一号断层平面上可分为三段两带,西段和西转换带为左旋走滑—伸展特征,伴生断层发育数量多,断层平面组合形式多样;中段为伸展特征,早期为单断模式,晚期伴生断层发育;东段和东转换带为右旋走滑—伸展特征,早期伸展断层,晚期右旋走滑作用明显。伸展和走滑作用在不同时期不同部位的强弱变化控制断层的发育,断层活动性和平衡剖面技术分析将断层演化过程划分为五个阶段,其中沙一二段沉积前受强伸展作用控制为主,东营组沉积期受强走滑—强伸展作用控制,新近纪受强走滑—弱伸展作用控制。石南一号断层控制了大量不同类型圈闭的发育,同时也是重要的油气运移断层。本研究成果深化了对石南一号断层的整体认识,对断裂带油气精细勘探具有重要意义。

The Shinan No.1 fault is a very important fault controlling sag formation and hydrocarbon accumulation in the north of Bozhong Sag in Bohai Sea area,and clarifying its static structural characteristics and dynamic evolution law is of significant guidance in intensive oil and gas exploration.According to the available exploration data,this paper systematically depicts the structure characteristics of Shinan No.1 fault,dissects its formation and evolution process and genetic mechanism,and analyzes its controlling effect on hydrocarbon accumulation.The study shows that Shinan No.1 fault can be divided into three segments and two zones on plane.The west segment and the west transitional zone are characterized by levorotary strike slip extension and developed with multiple associated faults in diverse plane patterns.The middle segment is characterized by extension,it is only a single fault in the early stage but develops multiple associated faults in the late stage;The eastern segment and the eastern transitional zone are characterized by dextral strike slip extension,and by extensional faults in the early stage and dextral strike slip in the late stage.The stress changes of extension and strike slip in different parts and different periods control the development of faults.The fault evolution process can be divided into five stages by analysis of fault activity and balanced cross-section technique.Among them,the fault development is controlled mainly by strong extension before deposition of the first and second member of Shahejie Formation in the early stage,by strong strike slip and strong extension in the sedimentary period of Dongying Formation,and by strong strike slip and weak extension in Neogene period.The Shinan No.1 fault controls the development of a large number of different traps,it plays an important role in oil and gas migration.The results concluded in this study are of great significance to promote the overall understanding to the Shinan No.1 fault and to the intensive exploration of oil and gas in fault zones.