Abstract: The cumulative hydrocarbon production in the oilfields in the eastern South China Sea has achieved nearly 400 million tons of oil equivalent over the years, making outstanding contributions to China’s energy security and economic construction. However, after more than 40 years of exploration and development, the remaining potential of conventional oil and gas is exhausted, and the deep oil and gas have become strategic replacements for guaranteeing sustainable reserves and production. This study focuses on the key issues encountered by oil and gas exploration in deep formations, such as basin formation, hydrocarbon generation, reservoir formation, and hydrocarbon accumulation. Using three-dimensional seismic, drilling data, and core analysis results, the hydrocarbon accumulation conditions in deep to ultra-deep reservoirs were systematically investigated from multiple perspectives, including the formation mechanism of hydrocarbon-rich sags/subsags, development mechanism of effective reservoirs, and hydrocarbon enrichment patterns. This provides new geological insights as below. (1)The composite continental-margin magmatic arcs control the formation and evolution of large lake basins. (2)Potassium-rich fluid transformation controls the development of effective reservoirs. (3)Seal and migration mechanism of transtensional fault systems controls hydrocarbon migration, accumulation, and enrichment. These findings guided the integrated evaluation and cluster drilling of the Huizhou 19-6 structure, leading to the discovery of billion-ton-scale oilfield in deep to ultra-deep clastic formations in China’s offshore area. The discovery of the Huizhou 19-6 structural oilfield further reveals that deep oil and gas of the Pearl River Mouth Basin are important replacements for the future growth of hydrocarbon reserves and production, demonstrating the huge exploration potential of deep to ultra-deep reservoirs in the offshore high-geothermal, highly tectonically active composite continental-margin basins, which provides important reference and inspiration for the exploration of petroliferous basins with similar structural settings.

Key words: South China Sea, Pearl River Mouth Basin, deep to ultra-deep formations, basin formation mechanism, reservoir stimulation, hydrocarbon accumulation conditions

摘要： 南海东部油田多年来的累计油气产量当量近4×10⁸t,为中国能源安全和经济建设做出了突出贡献,但历经40余年的勘探开发,其常规层系的油气勘探潜力殆尽,深层已成为储量和产量接替的重大战略领域。针对深层油气勘探面临的成盆、成烃、成储、成藏等关键问题,利用三维地震、钻井、岩心分析化验等资料,从富烃凹陷/洼陷形成机制、有效储层发育机理和油气富集规律等方面对深层—超深层油气的成藏条件开展系统研究,形成了复合陆缘岩浆弧结构控制大型湖盆的形成及演化、富钾流体改造控制高地温碎屑岩的有效储层发育、张扭型断裂体系封堵-运移机制控制油气运聚及富集等新认识,指导了惠州19-6构造的整体评价和集束钻探,在中国海上深层—超深层碎屑岩中发现了亿吨级油田。惠州19-6油田的发现进一步揭示了珠江口盆地深层是未来油气储量和产量增长的重要接替区,也展示了中国近海高地温、强活动型复合陆缘盆地深层的巨大勘探潜力,对相似构造背景下的含油气盆地勘探具有重要借鉴和启示意义。

关键词: 南海, 珠江口盆地, 深层—超深层, 成盆机制, 储层改造, 成藏条件