张扭性断陷盆地构造样式与油气成藏的关系——以珠江口盆地恩平凹陷新生界为例

STRUCTURAL STYLE IN A TENSION-SHEAR FAULT BASIN AND ITS BEARING ON HYDROCARBON ACCUMULATION:A CENOZOIC EXAMPLE IN ENPING SAG,PEARL RIVER MOUTH BASIN

从张扭性断陷盆地的断裂特征入手,结合构造动力学形成机制,总结了恩平凹陷的构造样式特征及有利圈闭类型,并探讨了构造样式对烃源岩的形成和油气富集区带的控制作用。结果表明:恩平凹陷为双向伸展的上下构造层变形系统的叠合,即古近系为NE—EW向伸展构造系统,新近系为NW—NWW向伸展—张性扭动构造系统;发育了4大类伸展型构造样式,构造样式演化控制了半地堑结构、烃源岩发育情况、油气的初始运移方向和断裂构造带与圈闭类型分布,为新生界油气藏的形成创造了有利条件。

Taking the Enping Sag as an example,we studied the structural characteristics of a tensionshear fault basin in this paper.Discussed are the influence of structural figuration and structural dynamics on the formation of hydrocarbon source rocks and hydrocarbon enrichment zone and the types of traps.The results show that there are 4kinds of extensional structural styles in the Cenozoic of the Enping Sag,which are constrained by a NE—EW extensional tectonic system in the lower tectonic layer and a NW—NWW tension-shear tectonic system in the upper layer,showing a combined structure of tectonic two-way stretch in general.The evolution of structural style constraints the development of the half graben and the formation and distribution of hydrocarbon source rocks as well as the formation of trap types and structural zones.It also determines the initial migration direction of hydrocarbon when it reaches the threshold of hydrocarbon generation.Therefore,the structural style has provided favorable conditions for the formation of Cenozoic oil and gas reservoirs in the study area.