歧口凹陷伸展滑脱构造系统的厘定及其地质意义

歧口凹陷是渤海湾盆地中部黄骅坳陷的一个次级凹陷,凹陷内蕴藏着丰富的油气资源,是渤海湾盆地油气勘探的重点区块。在叠前三维地震剖面精细构造解释分析的基础上,识别和建立了歧口凹陷伸展滑脱构造系统。该系统分为南部伸展滑脱系统和北部伸展滑脱系统,南部滑脱系统以羊二庄滑脱断裂为主体,连接张东断裂、张北断裂、赵家堡断裂等伸展断裂组合而成,北部滑脱系统以沧东断裂为主体,连接大张坨断裂、海河断裂、港西断裂、港东断裂、南大港断裂等伸展断裂构成。在平面上两大滑脱系统各自构成一个帚状断裂体系,在剖面上表现为叠瓦式几何形态,与次级断裂常构成"Y"型或复"Y"型组合样式,向深部会聚到主滑脱面。歧口凹陷古近纪时期变形基本都限定在区域性底滑脱界面之上,并具有多层次滑脱构造特征,控制和影响了歧口凹陷不同级别的构造形态和组合样式,同时对盆地的沉降过程也有重要的控制作用。歧口凹陷伸展滑脱构造为本区的油气储集和运移提供了有利条件,并初步探讨了歧口凹陷伸展滑脱构造的动力学条件。

The Redefinition and Geological Siginificance of Extensional Decollement Structure Systems in the Qikou Depression

The Qikou depression is a secondary depression of the Huanghua sag in the middle Bohai Bay basin which is abundant in oil and gas resources,and is one of the important hydrocarbon accumulation zones of the Bohai Bay basin. Extensional decollement structure system was recognized and determined by detailed tectonic interpretation and analysis of 3D prestack seismic data. The system can be divided to two parts:Southern and northern. The main part Yang′erzhuang decollement fault connected other faults consists of the southern system,such as the Zhangdong,Zhangbei and Zhaojiapu faults. Meanwhile,the northern system includes the Dazhangtuo,Haihe,Gangxi,Gangdong,Nandagang and Cangdong faults which is the main decollement fault and connects other secondary extensional faults. The two large decollement fault systems appeared as a penicillate fault system respectively on the plane and an imbricate arrangement on the profile. These main faults form a "Y" style or more complicated "Y" style with other secondary faults and converge to the main decollement plane downward. The deformation of the Qikou depression in the Paleogene was defined above the regional decollement base plane. The multi-level decollement structure controlled different grade tectonic shape,assemble styles of faults and subsidence of the Qikou depression. This extensional detachment is more beneficial to hydrocarbon migration and accumulation in the Qikou depression. And the dynamic conditions of the extensional decollement structure are preliminarily studied in Qikou depression.