辽河西部凹陷大洼地区沙三段陡坡带近岸水下扇识别与刻画

Identification and characterization of nearshore subaqueous fans in Es_(3) steep slope zone of Dawa Area in the Liaohe Western Depression

辽河西部凹陷陡坡带近岸水下扇扇体分布及其沉积相特征认识程度低。为了精细识别与刻画大洼地区沙河街组三段(沙三段)近岸水下扇,根据沉积物供给通道与地震属性研究,分析陡坡带近岸水下扇的沉积特征。结果表明:陡坡带具有构造变换控砂的特征,边界断层具有转换带特征,转换带地势平坦提供沉积物供给通道,物源沿通道入湖形成近岸水下扇沉积;陡坡带地震相特征指示近岸水下扇沉积,沿物源方向地震反射表现为斜交前积反射,垂直物源方向地震反射表现为杂乱丘型反射。陡坡带近岸水下扇具有区别于围岩的高波阻抗和强振幅属性特征,在低勘探程度区刻画两套扇体。该结果为研究陡坡带近岸水下扇油气勘探提供依据。

The distribution of nearshore subaqueous fan and its sedimentary facies characteristics in the steep slope zone of the Liaohe Western Depression are poorly understood.In order to accurately identify and characterize the nearshore subaqueous fans in the third member of Shahejie Formation in Dawa Area,the sedimentary characteristics of the fans in the steep slope zone of Dawa Area analyzed according to the study of sediment supply channels and seismic attributes.The results show that the steep slope zone has the characteristics of sand control by transformation structure,and the boundary fault has the characteristics of transition zone.The terrain of the transition zone is flat to provide sediment supply channels,and the source enters the lake along the channel to form nearshore underwater fan deposits.The seismic facies characteristics of steep slope zone indicate that the nearshore subaqueous fan deposits.The seismic reflection along the source direction is oblique progradation reflection,and the seismic reflection along the vertical source direction is chaotic hilly reflection.The nearshore subaqueous fans in the steep slope zone have the characteristics of high wave impedance and strong amplitude.Two sets of fans are characterized in the low exploration degree area.The results provide a basis for oil and gas exploration of offshore underwater fan in steep slope zone.