渤海湾盆地隐性断裂带识别及其地质意义

Identification of Potential Fault Zones and Its Geological Significance in Bohai Bay Basin

隐性断裂带是区域或局部应力场、基底断裂体系活动、潜山块体扭动影响下在沉积盆地盖层中产生的断裂趋势带,它是断裂带的一种类型,与显性断裂伴生于沉积盆地,但由于其不具有显性断裂的固有特征,隐蔽性强而常常被忽略.可以通过以下7个方面有效识别隐性断裂带:1小型显性构造(小断层、小褶皱、断块)呈雁列式、断续状、错位对称式反映的大型隐性断裂带;2基底断裂体系活动在沉积盆地盖层中产生的隐性断裂带;3潜山、凹陷分布形成的线状、调节型或者侧列式隐性断裂带;4砂体分布反映的隐性断裂带;5油藏排列、分布、走向反映的隐性断裂带;6相干体切片显示的隐性断裂带;7断层叠覆端、末端、深大断裂分段活动等局部应力场变化形成的隐性断裂带.应用上述方法开展渤海湾盆地隐性断裂带识别研究,综合国内外的调研结果,建立了隐性断裂带的类型划分方案体系并阐述了不同级别构造单元中隐性断裂带的类型特征.研究表明,隐性断裂带具有多方面的地质意义,可以作为调节构造带调节盆地不均匀伸展活动,分隔凹陷、隆起等构造单元;控制盆地沉积相带发育分布,影响断陷湖盆砂体的展布范围;控制圈闭组合排列、改造输导体系,形成串珠状、带状油气富集区;深断裂活动触发地震的过程中会在地表形成隐性断裂带,因此,隐性断裂带的识别和分析具有现实意义.

Potential fault zones refer to the fault zones which are influenced by regional or local stress field,basement rift activities,buried hill blocks twist and formed in the cover layer of sedimentary basin.It is a type of fault zone associated with dominant fault,which is often ignored because of the absence of inherent characteristics of dominant faults.It can be identified from 7 aspects below：1large potential fault zones reflected by en-echelon,intermittent,dislocation of symmetrical arranged small dominant structure（small faults,small folds,fault blocks）;2 potential fault zones produced by basement rift system activities;3linear,accommodated or side arranged potential fault zones formed by buried hills and sags;4 potential fault zones reflected by the distribution of sandstone bodies;5 potential fault zones reflected by the distribution,arrangement and strike of reservoirs;6 potential fault zones reflected by coherent body slices;7 potential fault zones formed by local stress field of overlapped fault,segment activities of deep and large faults.Taking the Bohai Bay basin as an example,a classification scheme of potential fault zone is established based on research results at home and abroad,and the characteristics of the potential faults in different levels of tectonic units are discussed.Potential fault zones are proved to be of geological significance in the following aspects.Firstly,it affects the tectonic pattern of basins by adjusting the inhomogeneous extension activities among different faulted blocks in basins and by separating the tectonic units such as sags and uplifts etc..Secondly,it determines the development and distribution of basin sedimentary facies and influences the distribution range of the sandstone in faulted basin.Thirdly,it yields bead string-like,belt-like,and ring-like oil-gas accumulation zones.The activities of deep faults are prone to induce earthquake and form the potential fault zones on the surface.Therefore,identification and analysis of potential fault zones can be important in reality.