琼东南盆地松东凹陷断裂发育特征

松东凹陷位于琼东南盆地东北部,是受琼东南盆地6号断裂控制、总体呈南断北超的新生代凹陷。松东凹陷断裂复杂,理清断裂的发育特征有助于加深对琼东南盆地区域构造演化的认识,具有重要油气地质意义。基于近几年新采集的地震资料,结合区域地质背景,从剖面上和平面上多方位对松东凹陷的各种类型断层进行了系统解释和厘定,分析了断裂的组合样式、活动期次、发育规律及展布特征。结果表明:松东凹陷单条断层剖面上多呈犁式、平直式,多条断层组合常呈复合"Y"字形、羽状、帚状和网状;平面上单条断层多为弧形、直线形,多条断层组合常呈帚状、斜交式和平行式;松东凹陷断层按期次可划分为始新世NE向、渐新世近EW向和中新世NWW向三组,NE向断层控制松东凹陷的边界及其内部次级构造,渐新世近EW向断层和中新世NWW向断层组合形成六组断裂带成排分布,并伴有多条近SN向走滑断层发育;松东凹陷不同期次断裂的发育是区域应力场伸展方向随时间发生顺时针旋转的结果。结合松东凹陷的断裂发育特征和成因机制分析,最终认为该区断裂对油气成藏起到控烃源、控运移和控圈闭的作用,SN向走滑断层周缘以及构造变换带是油气成藏有利位置。

Characteristics of faults in the Songdong sag of Qiongdongnan Basin

The Songdong sag, located in the northeast of Qiongdongnan Basin, is a Cenozoic depression controlled by the No. 6 fault and generally characterized by break in south and overlap in north. This sag hosts many complex faults. Clarifying the characteristics of these faults can help deepen the understanding of the regional structural evolution of Qiongdongnan Basin in relation to hydrocarbon geology. Based on the seismic data newly acquired in recent years and combined with regional geological background, this work systematically interpreted and determined various types of faults in this sag in horizontal and vertical directions, and revealed their combination style, active period, development law and distribution pattern. The results show that in vertical direction, the single fault sections in the sag are mostly of plough or straight shape, and the combination of multiple faults often looks like compound "Y" shape, pinnate, broom shape and network. On the plane, single faults are mostly of arc-shape and straight-line, and the combination of multiple faults is usually brush-like, oblique crossing and parallel. According to development stages, the faults can be divided into three groups: NE-trending of Eocene, nearly EW of Oligocene and NWW of Miocene. The NE-trending faults control the boundary of the Songdong sag and its internal secondary structures. The Oligocene EW and Miocene NWW faults jointly form six groups of fault zones. The development of faults in different stages in the sag is the result of clockwise rotation of the extension orientation of the regional stress field with time. Based on the analysis of fault development characteristics and genetic mechanism, it is concluded that the faults in this area play an important role in controlling hydrocarbon sources, migration and traps, and that the periphery of NS-trending strike slip faults and structural transformation zones are favorable locations for hydrocarbon accumulation.