Abstract: The granite buried hill area in the eastern deep water area of Qiongdongnan Basin has achieved major exploration breakthroughs, showing good exploration prospects. Based on geochemical analysis, using the latest drilling cores, logging, and seismic data, this paper analyzes the source of gas, key reservoir-forming conditions and the reservoir-forming model of buried hill in the Y8 block of Songnan low-uplift. The results show that the characteristics of carbon isotopes of gas, carbon isotopes of and biomarkers of gas condensate in the Y8 block are similar to those of gas and associated gas condensate in Songnan sag in the eastern deep water area, and quite different from those of L17 gas field and L18 gas field in Lingshui sag in the western deep water area. It reveals that the input of terrestrial organic matter in source rocks in the eastern deep water area is relatively more dominant and the gas in the Y8 block was mainly generated from Songnan sag. The basement of Songnan low-uplift is Indosinian granite, which is controlled by structure, lithology, weathering and leaching, and hydrothermal solution, forming the fracture-type and weathering-dissolution-type buried hill reservoirs and the nose structure ridge with a fishbone pattern. Fracture zones and deep faults in the basement constitute high-speed channels for oil and gas migration. The massive development of faults and fractures increases the contact area between source rocks and reservoirs. Due to the large source rocks-reservoirs pressure difference between the hydrocarbon generation center and the uplift area, the lateral relay-style long-distance migration of gas is from north to south, from the sag to the uplift area. The Y1 block near the sag on the Songnan low-uplift has great potential. The Mesozoic granite buried hill of the Songnan low-uplift is expected to become the next 100 billion cubic meter-level gas accumulation area in Qiongdongnan Basin.

Key words: Qiongdongnan Basin, Songnan low-uplift, deep water area, granite buried hill, accumulation model

摘要： 琼东南盆地深水区东区花岗岩潜山已获得重大勘探突破，显示了较好的勘探前景。基于地球化学分析，利用最新的钻井岩心、测井、地震等资料，分析了松南低凸起Y8区块天然气的来源、潜山的关键成藏条件及成藏模式。结果表明，Y8区块天然气的碳同位素、凝析油的碳同位素和生物标志化合物特征与深水区东区松南凹陷中天然气及伴生凝析油的特征类似，与深水区西区陵水凹陷中L17气田和L18气田的油气差异较大，揭示深水区东区烃源岩中陆源有机质的输入相对更占优势，Y8区块天然气主要来源于松南凹陷。松南低凸起的基底为印支期花岗岩，受构造、岩性、风化淋滤作用及热液溶蚀作用控制，形成了“裂缝+风化溶蚀型”潜山储层和“鱼骨刺”式鼻状构造脊。裂缝带和基底深大断裂构成了油气运移的高速通道。断裂与裂缝的大量发育增加了源、储的接触面积。生烃中心与凸起区的源-储压差大，天然气由北向南、由凹陷向凸起区呈长距离侧向接力式运移。松南低凸起上近凹陷方向的Y1区块具有较大潜力。松南低凸起的中生界花岗岩潜山有望成为琼东南盆地下一个千亿立方米级天然气聚集区。

关键词: 琼东南盆地, 松南低凸起, 深水区, 花岗岩潜山, 成藏模式