西江南半地堑晚期断裂系统基本特征及其控藏作用

 本文利用地震资料的构造解释和断裂系统的几何学、运动学对西江南半地堑晚期断裂的基本特征进行研究.研究表明,西江南半地堑晚期断裂是在NWW—SEE向张扭应力场作用下发生简单剪切右旋走滑变形形成和发育的.剖面上以负花状构造样式为主;平面上,主要呈NWW走向,断裂组合样式多样,包括平行式、交叉式、斜列式和羽状断层;断裂分布呈现明显分区特征,即晚期断裂主要分布在半地堑的南侧.结合圈闭定型期、油气充注史与晚期断裂活动的相关研究,晚期断裂系统对研究区控藏作用主要体现在3个方面：断裂控圈,即晚期断裂控制了新近系构造圈闭的形成及分布;部分断至古近系文昌组烃源岩内部甚至基底的晚期断裂和长期断裂一起构建了本区垂向优势运移通道,其它晚期断裂对早期油藏的二次调整、油气再运移及再聚集起重要的控制作用;主活动期后晚期断裂较好的侧向封闭性有效地控制了新近系油藏的最终聚集及分布.

Basic Features of Late-stage Fault System in Xijiang Southern Halfsraben and Its Controls on Hydrocarbon Accumulation

The basic features of late-stage faults are studied based on the structure interpretations of seismic data and geometry and kinematics of fault system. The results indicate that in the Xijiang southern half-graben, the majority of the late-stage faults trend towards NWW-SEE direction under the tensional shear stress field, showing negative flower structure in seismic profile and structural styles including parallel style, cross style, echelon style, and feather style, etc. in the section. The late-stage faults mainly distribute in the south side of the half-graben. Based on the related research on trap forming, timing of hydrocarbon filling, and activities of late-stage faults, the late-stage fault system mainly plays three important roles in oil accumulation. They are fault controlling trap, namely, the late-stage faults control the formation and distribution of Neogene structural traps, the oil migration and spatial distribution dominated by the late stage faults, the good fault sealing abilities; and ultimate hydrocarbon accumulation in Neogene strata controlled by the lat-stage faults.