南海北部大陆边缘琼东南盆地含油气系统

Petroleum System in Qiongdongnan Basin of the Continental Margin,the Northern South China Sea

以含油气系统理论为指导,从区域地质及沉积特征、烃源岩生排烃史、油气运移输导系统、油气形成与圈闭配置关系及油气运聚成藏组合模式等方面,对南海北部大陆边缘琼东南盆地不同含油气系统进行综合分析,划分圈定了北部浅水区含油气系统、中央坳陷带深水区含油气系统及南部深水区含油气系统,并进一步划分出13个亚含油气系统。由于不同含油气系统及亚含油气系统均存在明显差异,所以重点剖析了含油气系统中生烃子系统、油气运移输导子系统及油气运聚成藏子系统构成及其特点。结果表明:琼东南盆地生烃子系统主要由始新统中深湖相及渐新统煤系烃源岩之生烃灶所构成;油气输导子系统则主要由断裂及裂隙和连续性砂体、不整合、泥底辟、气烟囱等输导体系所构成,控制和制约了油气运聚的主要优势富集区;油气运聚成藏子系统以垂向和侧向运移方式为主,通过输导体系近源或远距离运聚,在圈闭及储盖组合条件极佳的优势区富集成藏。

Based on the theory of petroleum system, the different petroleum systems in Qiongdongnan Basin of the continental margin, the northern South China Sea were comprehensively analyzed by means of regional geology and sedimentary characteristics, history of hydrocarbon expulsion of source rocks, petroleum migration and conduction systems, configuration relationships between petroleum formation and traps, as well as the assemblages and modes of petroleum migration and accumulation. The petroleum system was divided into shallow water petroleum system in the northern depression, deep water petroleum system in the central depression and deep water petroleum system in the southern depression of Qiongdongnan Basin, and 13 petroleum sub-systems further. Because of the obvious difference between petroleum systems and petroleum sub-systems, the composition and characteristics of generation, migration and conduction, migration and accumulation sub-systems were analyzed. The results show that the generation sub-system is composed of Eocene mid-deep lacustrine facies and Oligocene coal series source rock kitchen; the migration and conduction sub-system consists of the pathway systems, including fault, fracture, continuous sand body, unconformity, mud diapir and gas chimney, and controls the main petroleum-bearing advantage region restrictively; the migration and accumulation sub-system is dominated by vertical and lateral migration pattern, and petroleum accumulation in the advantage area under the wonderful condition of trap and reservoir-caprock composition through the proximal or distal migration and accumulation of pathway systems.