走滑强控型盆缘洼陷控洼机制及主烃灶预测——以渤海盆地庙西南洼为例

研究渤海海域盆缘洼陷——庙西南洼的生烃能力,指导该区油气勘探。以三维地震资料为基础,利用剖面特征分析、古地貌恢复及水平方差切片分析等技术,对庙西南洼古近纪走滑、伸展等控洼断裂的活动期次、活动性质、活动强度进行研究,明确断裂的控洼机制,分析洼陷沉降中心的迁移规律,建立洼陷的演化模式,进而优选有利烃灶的发育位置。依据控洼断裂活动性质与强度的变化,可将其划分为4期构造运动:伸展主控期、伸展-走滑分异期、走滑-伸展联控期、走滑强拉期。不同期次的断裂活动导致洼陷结构的改变,使沉降中心不断迁移:孔店组-沙四段沉积时期中东部多沉降中心、沙三段沉积时期西南部沉降中心、东营组沉积时期南部沉降中心,呈现由东向西、由北向南的迁移规律,围绕走滑带往复迁移。中南次洼作为古近纪庙西南洼的继承性沉降中心,有利于烃源岩的成熟、保存,为研究区主烃灶发育区。

The depression-controlled mechanism and prediction of hydrocarbon kitchen in the strike slip fault-controlled marginal sag:A case study of the Miaoxi sag,Bohai Basin,China

The hydrocarbon generation capacity of Miaoxi Depression at the basin margin of Bohai Sea is studied in order to guide oil and gas exploration in the area.Based on the 3D seismic data,the tectonic activity stage and intensity of Paleogene strike-slip faults and extensional faults in Miaoxi sag are systematically studied through section analysis,paleogeomorphic restoration and seismic slice analysis.Then the migration law of subsiding center is analyzed,the pattern of basin evolution established,and the development position of quality hydrocarbon kitchen is determined.The results show that the tectonic activities in Miaoxi sag can be divided into extension-dominated stage,extension-strike slip differential stage,strike slip-extension joint control stage and strike slip-dominated stage in terms of the variation of fault properties and intensity.The fault activities of different stages lead to the change of the structures in the depression and make the constant migration of subsiding center.It reveals that the subsiding center is located in the central-eastern part of the sag during the depositional stage of Kongdian Formation and Sha 4 Member,in the southwestern part during the depositional stage of Sha 3 Member and in the southern part during the depositional stage of Dongying Formation,displaying a migration pattern from east to west,from north to south,and reciprocating migration around the strike-slip zone.As the center of inheritance subsidence in the southwest of Miaoxi during the Paleogene period,Zhongnan sub-sag is conducive to the maturation and preservation of source rocks,and is the development area of main hydrocarbon kitchen in the study area.