珠江口盆地东部海域天然气水合物成藏气源特征探讨  

Gas sources and its implications for hydrate accumulation in the eastern Pearl River Mouth Basin

作　　者：沙志彬[1,2] 许振强[3] 付少英[2] 梁金强[2] 张伟[2] 苏丕波 陆红锋 陆敬安[2] SHA Zhibin;XU Zhenqiang;FU Shaoying;LIANG Jinqiang;ZHANG Wei;SU Pibo;LU Hongfeng;LU Jing’an(China University of Geosciences(Wuhan), Wuhan 430074, China;MNR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Guangzhou 510760, China;China Geological Survey, Beijing 100037, China)

机构地区：[1]中国地质大学(武汉),武汉430074 [2]自然资源部海底矿产资源重点实验室,中国地质调查局广州海洋地质调查局,广州510760 [3]中国地质调查局,北京100037

出　　处：《海洋地质与第四纪地质》2019年第4期116-125,共10页Marine Geology & Quaternary Geology

基　　金：国家重点研发计划“中国海域冷泉系统演变过程及其机制”(2018YFC0310000);中国地质调查局项目“南海天然气水合物资源勘查”(DD20160211)

摘　　要：通过钻探,在珠江口盆地东部海域获取了天然气水合物实物样品,在5个取心站位目标层段进行了保压取心,获取了水合物岩心释放气样品,同时在13个层段获取了水合物分解气体样品。钻探取心的5个站位都在航次现场选择层段制备了顶空气样品。所有气体均进行了气体组成与同位素分析,结果表明:水合物气体组成以甲烷占绝对优势,甲烷含量96.5%~99.8%;乙烷含量极少,为(175~554)×10^-6,未检测出C2+以上烃类气体。水合物气体甲烷碳-氢同位素分析测试结果表明,δ13C1 为-68.4‰^-71.2‰,δDC1为-182‰^-184‰,据此判识水合物气体成因类型为生物成因气。水合物气源成因类型与水合物产出形态没有直接关系,多种产出类型的水合物可能与储层发育及形态特征有密切联系。主要气源位于1000m以内的浅地层中,主要以侧向运移方式运移至稳定域有利部位形成水合物。Pressure cores and void gas samples are collected by drilling from target layers at five coring sites in the eastern Pearl River Mouth Basin. Dissociation gas is also sampled in thirteen layers, while headspace gas samples acquired at all the five sites. All gas samples have been tested for chemical and isotopic compositions. The gas is methane dominated, which is up to 96.5%~99.8% in concentration. Trace amount of ethane is also detected in concentration of(175~554)×10^-6. No C2+ hydrocarbons have been found in all the gas samples. The isotopes of carbon and hydrogen of the methane suggest that δ13C1 is in the range of-68.4‰^-71.2‰, with δDC1 from-182‰ to-184‰, indicating a biogenic origin. The gas source of hydrate is not directly related to the occurrence of hydrate, while hydrate with multiple sources seems closely related to the evolution and morphological characteristics of reservoir. The main gas source area is located in the shallow strata less than 1000 m in depth, suggesting that the hydrocarbon has migrated to the favorable stability zone to form gas hydrate accumulation by shallow lateral migration.

关 键 词：天然气水合物 气源 成因类型 生物气 珠江口盆地东部海域 

分 类 号：P744[天文地球—海洋科学]