珠江盆地惠州凹陷古近系跷跷板式结构成因机制

南海北部裂陷期沉积充填是主要的烃源岩赋存层位,也是重要的油气产层,这类被动陆缘裂陷期结构对盆地充填具有重要的控制作用。利用大量地震剖面及钻井资料,对珠江口盆地惠州凹陷古近系裂陷结构进行了精细解剖。研究表明惠州凹陷古近系文昌期和恩平期2幕裂陷呈现出典型的跷跷板式叠置特征。文昌裂陷期在弥散式裂陷背景下发育了不同活动强度的南倾和北倾断层,形成多个孤立的小断陷;恩平裂陷期在拉张应力集中向南迁移至洋陆过渡带的背景下,南倾断层活动性强,北倾断层活动性减弱,这样2幕裂陷结构垂向叠置,形成了跷跷板式的凹陷结构样式。研究成果为南海北部大陆边缘盆地裂陷作用差异演化研究及油气勘探分析提供了新认识。

GENESIS MECHANISM OF PALEOGENE SEESAW STRUCTURE IN HUIZHOU SAG OF PEAR RIVER BASIN

The sedimentary infillings in riffing period in North.South China Sea are the main contained zones of the hydrocarbon source rocks,and moreover the important petroleum producing horizons,these kinds of the passive continental margin structures in the period possess the significant controlling actions on the basin infillings.With the help of the plentiful seismic profiles and drilling data,the fine analyses were conducted on Paleogene rifting structures in Huizhou Sag of Pearl River Mouth Basin.The researches show that the two riffing structures in Wenchang and Enping episodes indicate typical seesaw superimposed pattern in Paleogene Huizhou Sag:the former,the different-activities-strength S-dipping and N-dipping faults were developed in the background of the diffuse type of rifting;for the latter,the S-dipping fault activities grew stronger than those of the N-dipping faults,due to the intensive south migration of the stretching stress to the ocean-continental transforming belt,thus the two rifting structures were vertically overlaid and resulted in the seesaw sag structures.The study achievements show that the new understandings are provided for the study on the differential evolution of the rifting action and the analysis of the hydrocarbon exploration in the northern continental marginal basins of South China Sea.