琼东南盆地北部地区变换带构造特征及地质意义

Characteristics and significance of transfer zone in northern Qiongdongnan Basin,South China Sea

根据地震反射资料和断裂特征对琼东南盆地北部进行变换带的划分并分析其构造特征及地质意义。结果表明北部地区由松西—松东和宝岛变换带2个堑间变换带分为北断南超型崖北—松西半地堑、南断北超型松东半地堑和宝岛凹陷北斜坡南倾断阶3个不同类型的构造单元;根据边界断层和凹陷内部断层特征可划分出9个断层域和6个不同类型的断层域间变换带;琼东南盆地北部地区变换带呈近南北走向,宽度范围在T010反射层为2~14.8 km,剖面上普遍表现为低凸起形态;研究区变换带形成和演化主要与基底先存构造、断层分段生长和伸展方向以及伸展量有关;琼东南盆地北部地区构造格局主要是在南海晚渐新世南北向扩张作用下形成的;变换带在盆地演化过程中与主要伸展方向存在趋同的趋势;变换带发育时期处于紧邻生油凹陷的古构造高部位以及良好的储集条件,使其成为研究区有利油气富集区。

Based on seismic reflection data and fault characteristics,we firstly analyzed the transfer zone in the northern Qiongdongnan Basin,and then discussed its geological significance by integrating the regional background.The northern Qiongdongnan Basin can be divided into three different types of structural domains,i.e.,the Yabei-Songxi half graben,the Songdong half graben and the north slope of Baodao depression,which are separated by two interbasin transfer zones the songxi-songdong transfer zone and the baodao transfer zone.According to the characteristics of boundary faults and internal faults properties within the depression,the area can be further divided into 9 fault domains and 6 fault domain transfer zones.The transfer zones,striking north-south,presents widths varying from 2 to 14.8 km in T010 reflector,forming low uplifts in sections.The basement pre-existing structure,fault segment growth and extension factors were main factors influencing the formation and evolution of the transfer zones in the study area.By integrating the geological background,characteristics of faults and transfer zones,we speculate that the basin is generally formed under the north-south tensional stress in the South China Sea in the late Oligocene.The transfer zones tend to converge with the main extension direction of the basin.The transfer zones are always in the high position which is close to the oil kitchen sags,and usually have high quality reservoir properties.These conditions make transfer zones into hydrocarbon enrichment area.