珠江口盆地番禺4洼古近系文昌组构造-沉积耦合关系

Coupling relationship between structure and sedimentary of the Paleogene Wenchang Formation in Panyu 4 Sag,Pearl River Mouth Basin

番禺04地区位于珠江口盆地番禺4洼缓坡带,番禺4洼在新近系发现多个油田,为“小而肥”的富生烃洼陷,但是古近系勘探尚未获得突破。结合录井、测井、三维地震资料,对研究区构造特征及演化过程、物源体系以及沉积充填特征进行系统研究。结果表明:研究区文昌期受NW向F1断裂活动控制,经历强烈断陷期、断陷萎缩期的构造演化过程;物源主要来自北部西江中低凸起,母岩类型为花岗岩,碎屑物质搬运距离中等,成分成熟度较高;研究区NW向断裂在早期NWW-NW应力方向控制下先活化,近EW向断裂在晚期NW-NNW向应力控制下后活化。NW向主要断裂在文昌组沉积早期活动性强,文昌组下段发育断控型扇三角洲沉积体系,文昌组沉积晚期基本不活动,文昌组上段发育坡控型辫状河三角洲沉积体系,具备发育优质储层的条件;基于原型盆地恢复认为,研究区发育“早期断控、晚期坡控”的构造-沉积响应模式,文昌组上、下段表现出明显的差异沉积充填特征,存在由断控型扇三角洲向坡控型辫状河三角洲转变的特征。相对而言,文昌组上段辫状河三角洲前缘相带砂体具“旁生侧储、近源成藏”特征,且埋藏更浅,砂岩粒度和分选磨圆更优,勘探前景优于文昌组下段扇三角洲前缘砂体。

The Panyu 04 Area is located in the gentle slope zone of Panyu 4 Sag in the Pearl River Mouth Basin.Panyu 4 Sag has found having many oil fields in the Neogene,which is a"small and fat"hydrocarbon generating depression.However,no breakthrough has been made in the exploration of the Paleogene.Combining the well re-cording and logging,and 3D seismic data,the structural characteristics and evolution,provenance system,and sedimentary filling characteristics of the study area were systematically studied,the development and distribution of high-quality reservoirs explored,and their exploration potential analyzed.The results show that the NW-trend-ing F1 fault controlled the structure of the Panyu 04 Area.The Wenchang Period experienced a tectonic evolution from the initial to the peak stage of rifting,and to the shrinkage stage of rifting.The provenance is mainly from the middle-low uplift of the Xijiang River in the north,the parent rock is granite,the transportation distance of clastic materials is average,and the composition maturity is high.Influenced by the Huizhou Movement and the clock-wise transformation of regional stress field,the main faults in the study area are highly active in early Wenchang Period.The fault-controlled fan delta depositional system was developed in the lower Wenchang Formation,and was in overall inactive in late Wenchang Period.The slope-controlled braided river delta deposition system was developed in the upper Wenchang Formation,which favored high-quality reservoir development.Based on the restoration of prototype basin,we considered that the study area developed structural sedimentary pattern from early fault-control to late slope-control model.The upper and lower parts of Wenchang Formation show obvi-ously different sedimentary filling characteristics,and there is a transition from fault-controlled fan delta to slope-controlled braided river delta.The research results provide an important basis for the Paleogene exploration in the gentle slope zone of Panyu 4 Sag.