阿曼盆地北部古近系碳酸盐岩油藏成藏特征及主控因素

Characteristics and main controlling factors of hydrocarbon accumulation in Paleogene carbonate reservoir,north of Oman Basin

阿曼盆地发育多套成藏组合,油气资源丰富。前人研究主要集中于盆地内古生界和中生界成藏组合,对新生界成藏组合研究较少。结合区域构造演化、烃源岩分布、埋藏史等资料,以原油组分、岩心、测井和地震等资料为基础,对阿曼盆地北部古近系Umm Er Radhuma组碳酸盐岩储层开展研究,分析其储层特征、生烃来源、运移途径、成藏特征,建立成藏模式,探讨其成藏主控因素。结果表明:阿曼盆地北部古近系Umm Er Radhuma组碳酸盐岩储层埋藏浅、压实作用弱、孔隙发育,上部Rus组石膏层为其盖层,储盖条件优越;烃源为白垩系Natih组富含有机质的泥灰岩,生烃中心位于工区东部法胡德盐盆内。岩心地球化学分析表明:工区内烃源并未成熟,Umm Er Radhuma组油藏原油是法胡德盐盆烃源生烃后沿断层和不整合面向上、向西运移而来;白垩系顶部不整合面、溶蚀断裂塌陷通道及局部微构造是阿曼盆地北部古近系Umm Er Radhuma组碳酸盐岩油气成藏的关键因素,具有断裂沟通、沿不整合面运移、局部微构造控藏的特征。

Rich in hydrocarbon resource,Oman Basin develops multiple sets of hydrocarbon accumulation.The previous studies mainly focused on the source-reservoir assemblages in the Paleozoic and Mesozoic reservoirs,but less on those in Cenozoic reservoirs.In this paper,the Paleogene Umm Er Radhuma carbonate reservoir in the north of Oman Basin had been studied to analyze the reservoir characteristics,hydrocarbon resource,migration path,and accumulation features and establish hydrocarbon accumulation patterns to discuss the main controlling factors based on data about crude oil composi⁃tion,core,logging,and seismic combined with documents on regional tectonic evolution,source rock distribution and burial history.The results show the favorable reservoir-cap conditions.On one hand,the Paleogene Umm Er Radhuma carbonate formation in the north of Oman Basin is buried shallowly and compacted weakly with developed pores.On the other hand,the Rus gypsum horizon in the upper part can be used as the high-quality caprock.Also,according to the results,the hydrocarbon source is the organic-rich marl in the Cretaceous Natih carbonate formation and the hydrocarbon generation centeris located in the Fahud salt basin in the eastern work area.In accordance with the geochemical analysis of core,the hydro⁃carbon source in the work area is not mature;the crude oil in the Umm Er Radhuma carbonate reservoir is from the Fahudsalt basin in which the generated hydrocarbon is migrating upwards and westwards along the fault and plane of unconformi⁃ty.The plane of unconformity on top of the Cretaceous system,the collapse channel of dissolution fault,and local micro⁃structure are the key factors for hydrocarbon accumulation in the Paleogene Umm Er Radhuma carbonate reservoir in thenorth of Oman Basin and are characterized by“fault communication,migration along the plane of unconformity,and localmicrostructure in control”.