乌干达Albert湖凹陷北部沉积特征及油气成藏模式

乌干达Albert湖凹陷是世界上最年轻的生烃凹陷,受构造和沉积控制,油气多分布于北部构造调节带。为分析Albert湖北部构造调节带内部油气成藏特征,笔者利用地震、钻井、测井和孢粉等资料,开展北部构造调节带沉积特征研究,进而分析北部构造调节带的油气成藏模式。研究表明,由于边界正断层持续活动,北部构造调节带两侧沉积特征存在差异,研究区西部发育曲流河-三角洲沉积体系;东部发育冲积扇-扇三角洲沉积体系。由于北部构造调节带西部三角洲砂体向南推进至湖盆中心,与深湖相烃源岩直接沟通,成为Albert湖盆最有利的油气汇聚区。

Sedimentary characteristics and hydrocarbon accumulation model in northern Lake Albert sag,Uganda

Lake Albert sag is the youngest petroliferous sag.Due to its tectonics and sedimentation,oil and gas are mainly distributed in the northern accommodation zone.In order to analyze the characteristics of hydrocarbon accumulation in the northern accommodation zone,the authors studied the sedimentary characteristics by using the seismic,drilling,well logging and palynology data,then analyzed the hydrocarbon accumulation model of the northern accommodation zone.The results show that the continuous activity of the boundary normal faults resulted into different sedimentary characteristics on both sides of the northern accommodation zone.The meandering river-delta depositional system is developed in the west,while the alluvial fan-fan delta depositional system is developed in the east.Because the delta sand body in the west prograded southward to the center of the lake,and directly connected with the deep lacustrine source rocks,it became the most favorable hydrocarbon accumulation area in the Albert Lake.