渤海东部庙西地区隆凹结构的形成及与油气聚集的关系

Formation of uplifts and sags in Miaoxi area of eastern Bohai Sea and their relationship with hydrocarbon accumulation

通过LA-MC-ICP-MS锆石U-Pb定年测试,得出渤海东部庙西地区基底花岗岩形成于中—晚侏罗世(161 Ma左右)。通过三维地震资料解释和绘制该区新生界厚度图,揭示出庙西地区具有典型的断坳结构,主要经历了中生代末的基底形成期、新生代的断陷期和坳陷期3个阶段。构造演化对油气聚集产生了重要影响,主要表现在:中—晚侏罗世基底的形成奠定了后期构造演化的基本格局;断陷期形成了沙河街组和东营组烃源岩;坳陷阶段开始了油气的生成与排替。凸起和斜坡区深浅层形成了大量与断裂相关的断背斜、断鼻和断块圈闭;不同级别的断层对油气运移作用不同,一、二级主干断裂沟通源岩,将油气运移至有利圈闭,三级断裂则将油气封堵聚集成藏。

According to LA-MC-ICP-MS zircon U-Pb dating, the granite base in the Miaoxi area of the eastern Bohai Sea deposited during the Middle and Late Jurassic （ about 161 Ma） . Based on 3d seismic data interpreta-tion, the thickness map of Cenozoic strata was drawn, showing typical faulted depression in the study area. The Miaoxi area has experienced 3 evolutionary stages：the basement formation stage at the end of Mesozoic, the faulted stage and the depression stage during Cenozoic. Structural evolutions had significant impacts on hydrocarbon ac-cumulations. The basement formation during the Middle and Late Jurassic established the basic foundation for the latter structural evolution. During the faulted stage, the source rocks of the Shahejie and Dongying Formations de-posited. During the depression stage, hydrocarbon generation and expulsion occurred. A large number of fault-re-lated traps including faulted-anticlines, fault noses and fault blocks were formed in deep and shallow layers of uplifts and slopes. Faults of different orders played different roles in hydrocarbon accumulation. Major faults of the first and second orders connected source rocks and reservoirs, making hydrocarbon migrate to favorable traps. Faults of the third order plugged hydrocarbon.