珠江口盆地陆丰凹陷古近系与新近系油气富集规律的差异及其主控因素

珠江口盆地陆丰凹陷同时发育古近系文昌组油藏、恩平组油藏和新近系珠江组油藏，不同层系表现出不同的油气富集规律。在古近纪强烈裂陷阶段形成的文昌组深湖相泥岩具有厚度大、有机质丰度高的特点，是陆丰凹陷油气的主要来源。古近系油藏埋深较大，主要分布在洼陷斜坡和洼中隆起位置；新近系油藏埋深较浅，主要分布在远离洼陷的凸起带。古近系储层主要为湖相三角洲成因，埋深较大，物性相对较差；新近系储层主要为海相沉积，埋深较浅，物性相对较好。新近系圈闭的形成主要受构造控制，发育背斜和断背斜圈闭；古近系圈闭的形成往往受构造和岩性共同控制。包裹体分析表明，不同含油层系具有不同的成藏时间，文昌组、恩平组和珠江组分别在12 Ma、11 Ma和9 Ma成藏。古近系油藏和新近系油藏具有不同的运移输导特征，砂体和断裂的组合构成了多种输导模式。古近系油藏具有近源运聚成藏的特征，以短距离的砂体侧向输导和断裂垂向输导为主；而新近系油藏表现为远源运聚成藏的特征，砂体和控洼断裂构成复合运移通道。不同的油气富集规律导致古近系和新近系油藏具有不同的成藏主控因素。其中，文昌组油藏主要受控于储层发育特征，恩平组油藏主要受控于储-盖组合，而珠江组油藏主要受控于圈闭发育条件。

Differences of hydrocarbon enrichment regularities and their main controlling factors between Paleogene and Neogene in Lufeng sag,Pearl River Mouth Basin

The reservoirs in Paleogene Wenchang Formation, Enping Formation and Neogene Zhujiang Formation are simultaneously developed in Lufeng sag of Pearl River Mouth Basin, and different layers show different oil and gas enrichment regularities. The deep lacustrine mudstone of Wenchang Formation was formed in the Paleogene intense rift stage, characterized by great thickness and high abundance of organic matter, as the main source of oil and gas in Lufeng sag. The Paleogene reservoir had a deep burial depth, mainly distributed on the slope and in the central uplift of subsag. The Neogene reservoir had a shallow burial depth, mainly distributed in the uplift area away from the subsag. The Paleogene reservoirs were mainly sourced from the lacustrine delta with deep burial depth and relatively poor physical properties. The Neogene reservoirs were dominated by marine sediments with shallow burial depth and relatively good physical properties. The formation of Neogene traps was mainly controlled by geological structures; anticline and fault anticline traps were developed. The formation of Paleogene traps was often controlled by geological structures and lithologies. The fluid inclusion analysis showed that different oil-bearing strata had different accumulation time, and Wenchang Formation, Enping Formation and Zhujiang Formation were formed at 12 Ma, 11 Ma and 9 Ma respectively. The Paleogene and the Neogene reservoirs had different migration and transport characteristics, and the combination of sand bodies and faults constitutes multiple transport modes. The Paleogene reservoirs were characterized by near-source transport and accumulation, especially short-distance sand-body lateral transport and vertical fault transport, while the Neogene reservoirs are characterized by far-source transport and accumulation. The sand body and subsag-controlling fault constitute composite migration channels. The differences in oil and gas enrichment regularities lead to different main controlling factors of hydrocarbon accumulation in the Paleogene and Neogene reservoirs. Thereinto, the reservoirs of Wenchang Formation, Enping Formation and Zhujiang Formation are mainly controlled by reservoir development characteristics, reservoir-cap combination, and trap development conditions, respectively.