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在对琼东南盆地宝岛北坡最新油气勘探资料分析基础上,通过比对宝岛北坡A区和B区的油气地球化学特征,利用Knipe三角图和断层连通概率法(FOI)综合评判地区断层封闭性,最后结合油气成藏期、断层主要活动期、沉积相等地质特征,分析宝岛北坡断层封闭性对地区油气运聚产生的影响。结果表明:宝岛北坡A区天然气具有重烃含量高、非烃含量低、碳同位素组成轻且凝析油中不含C30-4甲基甾烷和双杜松烷的特征,这与B区有明显区别;研究区内断层主要活动期为三亚组(T50—T60)沉积时期,在晚期的油气运聚高峰期时断层主要是静止的;现今断层具有分段封闭性的特征,深部断层封闭性较差成为沟通烃源岩和储层的良好通道;断层的分段封闭性特征造成了宝岛A区和B区油气不同的运聚方式,从而导致了气藏中油气性质的不同。
Based on the latest oil and gas exploration data on the northern slope of Baojao in the Qiongdongnan Basin, the geochemical characteristics of oil and gas in areas A and B of the northern slope of the island were compared by Knife triangulation and the method of fault connectivity (FOI) Finally, combining with the hydrocarbon accumulation period, the main active period of the fault and the sedimentary equivalent geological features, the influence of fault sealing on the hydrocarbon migration and accumulation in the north of the island is analyzed. The results show that the natural gas in A zone of the northern slope of the island has the characteristics of high heavy hydrocarbon content, low non-hydrocarbon content, light carbon isotope composition and no C30-4 methylstestane and bis-junbon in condensate oil, (T50-T60) during the depositional period of the Sanya Formation (T50-T60). In the late period of oil and gas migration and accumulation, the faults are mainly quiescent; today’s faults are characterized by fault-block sealing. Deep faults The poor sealing property has become a good channel for communication between source rocks and reservoirs. The segmented sealing characteristics of the faults have resulted in different modes of hydrocarbon migration and accumulation in Zone A and Zone B of the island, resulting in different oil and gas properties in the reservoir.