东海西湖凹陷原型盆地构造格架与演化分析

随着当前东海西湖深层油气勘探新突破,西湖凹陷又成为海域石油地质研究的重点区域。在依据近年来最新的二维、三维地震资料解释成果的基础上,对西湖凹陷新生代原型盆地的构造格架进行全面分析,深化了断陷、拗陷、区域沉降期的沉积格架、断裂及演化特征分析。研究认为西湖凹陷古新统与中下始新统宝石期原型盆地具多断洼并列发育特征,而始新统平湖组中上段具转换陆缘拗陷特征,反映出盆地演化从不稳定的多断陷沉降格局变格为统一拗陷的重要阶段;中央背斜带早期发育多个雁列式凸起,中新世末受挤压走滑构造发生反转,在拗陷中心形成大型冲断背斜带,是西湖凹陷形成大型气田有利的勘探构造区带。

Analysis of Tectonic Framework and Evolution of Prototype Basin in Xihu Sag of the East China Sea

With the new breakthrough in oil & gas exploration in deep strata of Xihu Sag in the East China Sea, Xihu Sag has become the key area for offshore petroleum geological study. Based on the latest 2D and 3D seismic data interpretation result, a comprehensive analysis has been conducted on the structural framework of prototype Cenozoic basin in Xihu Sag, the sedimentary framework, fault and evolution characteristics during the period of faulting depression, depression, and regional subsidence. The study indicated that the prototype basin during the Palaeocene and Middle-Lower Eocene Baoshi Age was characterized by development of several faulted sags in Xihu Sag, while during the sedimentation of Upper and Middle Pinghu formation within Eocene, conversion epicontinental depression was developed, reflecting the important stage of the basin evolution from the unstable subsidence of multiple fault sags to stable unified depression. Early echelon bulges developed in the central anticline belt, the structural inversion occurred caused by extrusion strike-slip at the end of the Miocene, forming the large thrust anticline belt in the center of depression, which is favorable exploration tectonic zone forming large gas fields in Xihu Sag.