摘要
东非裂谷系盆地近年来取得多个油气发现,Tanganyika盆地南部研究区根据地震特征可划分为缓坡带、洼陷中心、剪切带三个构造单元,构造特征与已发现含油气盆地相似,具有较大的勘探潜力。根据地震反射界面接触关系及界面上下剖面反射特征,识别出4个层序界面:T 14、T 12、T 5、T 2,相应地将盆地沉积地层划分为4个三级层序:SQ 1~SQ 4。在层序格架控制下,根据地震相外部反射形态及内部反射结构,识别出河道充填状、强振幅席状、弱振幅席状、楔状、透镜状、丘状、叠瓦状7种地震相类型,分别代表河流、滨浅湖-深湖、深水等深流、扇三角洲等不同沉积体系。研究结果表明:研究区SQ 1层序时期,缓坡带孤立半地堑发育三角洲沉积,洼陷中心以滨浅湖-深湖相沉积为主;SQ 2层序时期缓坡带作为统一的构造单元发育河流及三角洲沉积,洼陷中心以发育三角洲及浊流相沉积为特征;SQ 3层序时期构造抬升,缓坡带发育大型曲流河沉积,洼陷中心三角洲及浊流沉积规模进一步扩大;SQ 4层序时期裂陷进一步加剧,洼陷中心发育洼陷中心发育深水等深流沉积,边界断层陡坡带发育大规模扇三角洲及滑塌沉积。研究成果将为盆地下一步的油气勘探提供理论支持。
Series of oil and gas exploration discovery is in East Africa System in recent years.The Tanganyika basin is with great petroleum exploration potential,because its structures are similar with these petroliferous basins with three units of gentle slope belt,sag subsidence center and shear zone.Four reflectors were identified including T 14,T 12,T 5 and T 2,which corresponded to four third-order sequences namely SQ 1,SQ 2,SQ 3 and SQ 4,according to the seismic reflection characters and interface contact relationship.Under the control of sequence framework,based on seismic reflections external and internal characters,seven types of seismic facies were identified,which included channel filling seismic face,strong amplitude sheet seismic face,weak amplitude sheet seismic face,wedge shaped seismic face,lenticular shaped seismic face,mound-shaped seismic face and imbricate seismic face.Those facies reflected river,shallow to deep lacustrine,contourite and fan delta sedimentary systems.The following results are gotten from the research.During the sedimentary period of the SQ 1,deltas are developed in the isolated half grabens on the gentle slope,and shallow-deep lacustrine deposits in the center of the sag.When the SQ 2 deposited,fluvial and delta deposits are developed in the gentle slope zone as a unified tectonic unit,and delta and turbidite deposits in the center of the sag.During the depositionary period of the SQ 3,as the structure uplifted,large meandering rivers appear in the gentle slope zone,and delta and turbidite deposits further expand in the center of the sag.With the coming of the SQ 4,contourite is developed in the center of the sag and large fan deltas and slump deposits in the steep slope of the boundary fault,resulted by the reactive rifting.The results could provide theoretical support for the oil and gas exploration in the basin.
作者
周超
张宁宁
曾倩
孟德伟
ZHOU Chao;ZHANG Ning-ning;ZENG Qian;MENG De-wei(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;China National Oil and Gas Exploration and Development Ltd.Corporation,Beijing 100034,China;Petrochina Research Institute of Petroleum Exploration and Development,Beijing 100083,China)
出处
《科学技术与工程》
北大核心
2020年第24期9757-9763,共7页
Science Technology and Engineering
基金
国家科技重大专项(2016ZX05029)。
