南海北部琼东南盆地天然气水合物气源及运聚成藏模式预测

南海北部琼东南盆地南部深水区流体活动强烈，天然气水合物（以下简称水合物）气源岩类型多，气源供给系统及运聚条件良好，是我国深水水合物资源的重要远景区之一。为深入研究该区水合物的形成条件及资源潜力，根据盆地构造沉积演化及油气地质条件与多年来的油气勘探成果，分析了该区天然气的成因类型和资源潜力；根据高分辨率地震解释资料，重点剖析了气源供给的运聚通道系统与水合物成藏的耦合关系；最后结合水合物成藏地质条件，探讨了水合物的成藏模式。结果表明：①该区热解气和生物气气源充足、资源潜力大，能够为水合物的形成提供充足的烃源供给；②天然气运聚系统较优越，存在生物气源自生自储型、热解气源断层裂隙下生上储型和热解气源底辟及气烟囱下生上储型3种类型的水合物成藏模式；③深水区热解气源下生上储型水合物，其热解气源输送运聚通道主要为断层裂隙和泥底辟及气烟囱所构成的纵向运聚供给系统，其形成展布及优劣，主要取决于构造沉积演化、断裂活动和活跃地质热流体异常侵入活动。

Prediction of gas sources of natural gas hydrate in the Qiongdongnan Basin,northern South China Sea,and its migration,accumulation and reservoir formation pattern

The fluid activity is intense in the abyssal zone in the southern part of the Qiongdongnan Basin, northern South China Sea, and natural gas hydrates are characterized by multiple types of source rocks, good gas source systems and favorable migration and accumulation situations, so this area is one important prospect of abyssal hydrate resources. In order to further investigate the hydrate forming conditions and resource potential in this area, this paper first analyzes genetic types and resource potential of natural gas in this area based on structural and sedimentary evolution and geologic conditions of this basin and years of oil and gas exploration achievements. Second, it mainly analyzes the coupling relation between source gas migration and accumulation pathways and hydrate reservoir formation by using high-resolution seismic interpretation data. And finally, it probes into hydrate reservoir forming patterns on the basis of geologic conditions for the formation of hydrate reservoirs. Results show that there are sufficient pyrolysis gas and biogas sources and resource potentials, which means sufficient source supply for the formation of hydrates. Besides, there are favorable gas migration and accumulation systems. Three hydrate reservoir forming patterns are established, including biogas sourced self generation - self pyrolysis gas sourced lower generation – upper storage with faults and fractures, and pyrolysis gas sourced lower generation – upper storage with diapers and gas chimneys. What's more, as for the pyrolysis gas sourced lower generation – upper storage hydrate in abyssal zones, the pyrolysis gas source migrates and accumulates mainly along vertical migration and accumulation system which consists of faults, fractures, diapers and gas chimneys, so its extension and performances are mainly controlled by structural and sedimentary evolution, fracturing activity and abnormal intrusion of geologically active thermal fluids.