惠民凹陷西部深层断裂样式与古近纪盆地原型的性质

摘要

Based on the mechanics analysis of fault formation, a systematic study of the fault styles of the deep part of the western Huimin depression, including the basin basement, the Kongdian group ( Ek), and the fourth member of the Shahejie group ( Es4 ), was carried out.The main features of faults within the depression, including their distribution, timing of activity, and their influence on the Paleogene basin that evolved into the western Huimin depression, were constrained by interpretations of horizontal slices and cross-sections of 3D seismic data, and the analysis of regional tectonic maps.Also the cause of fracture formation, the nature of the Paleogene prototype basin, and the control of faulting on the formation of oil-gas reservoirs were considered.The results reveal two types of deep fractures in the western Huimin depression, based on tectonic style: strike-slip and extensional.The formation of basement faults was related to sinistral strike-slip movement along the Tan-Lu fault and counter-clockwise rotation of the Luxi uplift during the late Yanshanian, and the fault style during Ek-Es4 sedimentation was closely related to NNW-SSE extension and dextral strike-slip movement upon large deep-level faults ( e.g., the Tan-Lu fault).The distribution and sedimentary characteristics of deep-level faults indicate that the formation of the Paleogene precursor basin in the western Huimin depression was closely related to strike-slip faulting, suggesting the precursor busm was a transtensional structure rather than a purely extensional structure.The style of deep-level faults controlled not only the internal structures of the basin, but also the distribution of sandy layers, which provided a pathway of oil and gas migrating toward areas with shallowly dipping beds, thereby ultimately controlled the formation of oil and gas reservoirs.%基于断裂构造形成的力学分析,通过对三维地震数据体的水平切片及剖面的解译、区域构造图的编制,系统研究惠民凹陷西部深层(基底、孔店组-沙四段(Ek-Es4))断裂样式,并对其组合特征、分布规律、活动性质及对古近纪原型盆地形成的影响进行分析,探讨断裂成因、古近纪原型盆地的性质及对油气藏形成的控制作用.结果表明:惠民凹陷西部深层断裂样式可划分为走滑成因断裂样式与伸展成因断裂样式两种类型;基底断裂样式的形成与燕山末期郯庐断裂的左行走滑及鲁西隆起的逆时针旋转趋势相关,孔店组-沙四段沉积期断裂样式与NNW向伸展及郯庐断裂等深大断裂右行走滑作用叠加密切相关;深层断裂样式的特点、分布及沉积特征反映惠民凹陷西部古近纪原型盆地形成过程与走滑作用密切相关,盆地原型应为走滑-伸展型盆地,而非单一的伸展型盆地;深层断裂样式不仅控制了盆地的内部结构,也控制了砂体的分布,并为油气向缓坡带运移提供了通道,从而最终控制了深层油气藏的形成.