北部湾盆地迈陈凹陷东部地区油气成藏特征

Characteristics of hydrocarbon pooling in the east of the Maichen sag of the Beibu Gulf Basin

在区域构造演化、构造单元划分及地层发育特征分析的基础上,对北部湾盆地迈陈凹陷东部地区,重点开展了储集层、油气成藏条件和主控因素研究,建立起研究区油气成藏模式。分析认为,古近系流沙港组、涠洲组是主要含油层系,包括4套储盖组合;主要烃源岩为流二段和流三段上部暗色泥岩,2套重要的砂岩储层是流三段和涠洲组;圈闭类型以断鼻、断块及地层超覆型为主,时间、空间上配置较好;成熟烃源岩、储层发育、断层特征、盖层条件和圈闭形态及落实程度是油气成藏的主控因素;研究区包括深凹带内斜坡带、南部断阶带和外斜坡、远斜坡带三种成藏模式,内斜坡带西部地区为勘探最有利的区带。

Based on the analysis of regional tectonic evolution, structural unit division and characteristics of strata development, the reservoirs, hydrocarbon pooling conditions and main controlling factors were studied to set up pool-forming models in the east of the Maichen Sag of the Beibu Gulf Basin. The Paleogene Liushagang and Weizhou formations （ El and Ew respectively） are the dominant oil-bearing formations which include four sets of reservoir-seal combinations;the dark mudstone in the El^2 and the upper El^3 are the main source rocks;the El^3 and Ew are two important sandstone reservoirs. The traps are mainly faulted nose, faulted block and stratigraphic overlap traps with good timing and spatial configurations. The predominant factors controlling pool-forming could be mature source rocks, reservoirs development, fault features, sealing conditions, configuration of traps and their workable degree. There are three hydrocarbon pooling models, including the inner-slope zone in the deep sag, fault bench in the south, outer-slope and far slope zone. The western part of inner slope zone is the most favorable area for further exploration.