珠江口盆地番禺4洼陷文昌组沉积充填模式

Sediment Filing Model for Wenchang Formation in Panyu-4 Sub-Sag,Pearl River Mouth Basin

珠江口盆地珠一坳陷西江凹陷番禺4洼陷目前尚属油气勘探初期,开展沉积充填研究对其勘探具有重要意义。基于构造和沉积充填对层序的控制作用,综合利用三维地震和少量钻井、测井、岩心资料,将古近系文昌组划分为3个三级层序,分析各层序地震相及沉积相发育特征,进而总结沉积充填模式。研究结果表明:番禺4洼陷由南东向北西依次发育陡坡带、深凹带和缓坡带,各级同生调节断层的分布和组合样式控制了沉积体系的发育和展布;东南缘陡坡区主要发育近岸水下冲积扇-近岸水下浊积扇体系;西北缘缓坡区次级调节断层导致南北沉积差异,北部因断层发育形成构造坡折,远岸水下浊积扇和滑塌浊积体广泛分布,南部缓坡未受断层影响,沉积大型河流三角洲体系;湖盆中心发育半深湖-深湖相泥岩。

Panyu-4 sub-sag of Zhuyi depression in Pearl River Mouth basin is in early stage of exploration.Carrying on sedimentary filling research is of important significance for its prospecting.Based on tectonics and sequence stratigraphic control on the sedimentary filling,using the 3D seismic data,drilling,well logging and core data,the Paleogene Wenchang formation was divided into 3 third-order sequences,and their development characteristics of seismic facies and sedimentary facies were analyzed,and the sag＇s sedimentary filling model was presented finally.It is indicated that in Panyu-4 sub-sag,steep slope zone,depression zone and gentle slope zone occur from southeast to northwest in turn,and the development and distribution of sedimentary systems are controlled by the distribution and combination of syngenetic accommodation faults of all levels,and nearshore underwater alluvial fan and nearshore underwater turbidite fan systems occur in the steep slope zone;the secondary accommodation faults of northwestern gentle slope zone result in the depositional differences from the south to the north;the structural slope break is formed due to faults to the north,and offshore underwater turbidite fan and fluxoturbidite are distributed widely;the gentle slope in the south is not affected by the fault,where large-scale river deltas are developed;and the semi-deep and deep lake shale occur in the center of lake basin.