断陷盆地边界断层分段的层序地层响应特征——以南堡凹陷西南庄断层上盘陡坡带东营组为例

通过综合3D地震数据及钻井资料,以三级层序为时间单元制作了不同时期断层位移曲线和断面倾角分布图,对西南庄断层分段的断面几何学与东营组时期运动学特征进行分析。结果表明西南庄断层分段控制了其上盘褶皱几何形态。其中,向斜(半地堑)位于断层位移极大段,背斜位于断层位移极小处即断层段连接处;断层分段的几何学与运动学特征具有明显对应关系,在位移极大段,断层面较陡,而断层段连接处,断层位移较小,对应的断层倾角也较小。边界断层分段活动控制了盆地内可容纳空间、物源供应和古地貌。在断层段中央附近断层活动速率最大,物源供应速率最低,可容纳空间一直是增长的,层序内部准层序以退积和加积式叠置方式为主。而断层段连接处,断层活动速率最小,物源供应速率最高,可容纳空间以下降为主,层序内部准层序以进积式叠置方式为主。因此,沿边界断层走向断层活动性差异控制了层序内部构成样式,是控制断陷盆地陡坡带储层和烃源岩发育的主要因素。

Architecture of Sequence Stratigraphy Responding to Segmentation of Boundary Fault:Taking an Example of Dongying Formation on Hanging Wall of Xinanzhuang Fault in Nanpu Sag

We investigated the control of boundary fault segmentation on architecture of sequence stratigraphy in continental rift basin.Integrating 3D seismic and well data to construct map of displacement along strike on unit of third order sequence stratigraphy and dip angle on fault surface,the segmentation of Xinanzhuang fault (XNZHF) is examined based on geometry of fault surface and kinematics in period of Dongying Formation.XNZHF comprises linked segments and is an important control on hanging wall fold geometry.Synclines form at local displacement maxima,located at the centers of the fault segments,anticlines form at local displacement minima,located where fault segments link.The corrugations of fault surface apparently correlates with displacement variation,local displacement maxima corresponds with high dip angle of fault surface and the minima corresponds with low dip angle.Fault growth is a prime control on accommodation,sediment supply and physiography.High displacement rate and low sediment supply at the center of fault segment lead to predominantly aggradational/retrogradational para-sequence stacking patterns.Whereas low displacement rate and high sediment supply at boundary of fault segments show result in primarily progradational stacking patterns.The segmentation and displacement variation along strike control the stacking patterns inner sequence and is the prime control on the sand and source rock dispersal on the hanging wall of XNZHF.