北部湾盆地乌石凹陷东区断裂类型及其形成演化

Types and evolution of faults in the east area of the Wushi Sag,Beibuwan Basin

受多重构造作用影响,北部湾盆地乌石凹陷形成了复杂的内部构造,准确识别不同期次构造发育特征对于油气勘探具有重要意义。文中运用高精度三维地震、钻井等资料系统分析了乌石凹陷东区断裂类型、组合样式、形成演化规律及其动力学成因机制。分析结果表明:在太平洋板块、印度板块和欧亚板块间相互作用产生的伸展-走滑-弱挤压联合叠加区域应力影响下,乌石凹陷东区发育伸展、走滑和挤压3套断裂系统,并形成相应的13种平、剖面断裂组合样式;断裂形成演化共经历5个主要阶段:古新世伸展萌芽阶段、始新世伸展主活动阶段、早(中)渐新世走滑弱伸展阶段、晚渐新世走滑弱挤压阶段和新近纪以来的定型保留阶段。

Affected by multiple stages of tectonic movements,the Wushi Sag in the Beibuwan Basin has formed complex internal structures.Accurately identifying the structural development characteristics of different stages has a great significance for oil and gas exploration.In this paper,we used the high-precision 3D seismic and drilling data to analyze the fault type,combination pattern,evolution rule and dynamic mechanism in the east area of the Wushi sag.The results show that under the influence of the regional stress of extension-strike-slip and weak compression caused by the interaction between the Pacific plate,the Indian plate and the Eurasian plate,three sets of extension-strike-slip-compression fault systems were developed in the east area of the Wushi sag,and 13 types of plane and profile fault combinations are identified.The formation and evolution of the fault system endured five main stages,including the initial weak rifting stage in the Paleocene,the main extension stage in the Eocene,the strike-slip and weak extension stage in the Early and Middle Oligocene,the strike-slip and weak compression stage in the late Oligocene,and the final stage since the Neogene.