南海北部高饱和度水合物矿藏的烃类气体来源与成因机制  

Origin and genetic mechanism of hydrocarbon gas sources of the highly saturated gas hydrate deposits in the northern South China Sea

作　　者：赖洪飞 匡增桂[1] 方允鑫[1] 许辰璐 任金锋[1] 梁金强[1] 陆敬安[1] LAI Hongfei;KUANG Zenggui;FANG Yunxin;XU Chenlu;REN Jinfeng;LIANG Jinqiang;LU Jing'an(National Engineering Research Center of Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,Guangzhou 511458,China)

机构地区：[1]广州海洋地质调查局天然气水合物勘查开发国家工程研究中心,广东广州511458

出　　处：《地学前缘》2025年第2期36-60,共25页Earth Science Frontiers

基　　金：国家重点研发计划项目(2021YFC2800901,2024YFC2814701);广东省基础与应用基础研究基金项目(2022A1515110569,2023A1515010913,2023B0303000015);天然气水合物勘查开发国家工程研究中心青年研究团队项目(NERC2024001);广州市科技计划项目(202201011396);中国地质调查局项目(DD20221705,DD20230064)。

摘　　要：天然气水合物形成的物质来源对揭示其富集成藏机制至关重要。南海北部已钻探证实存在大量高饱和度天然气水合物矿藏,但其成矿烃类气体来源与成因机制仍未被系统阐明,制约着主力气源的判识和未来勘查部署。本文以南海北部琼东南和神狐海域典型的高饱和度水合物矿藏为研究对象,采用气体地球化学、沉积物有机地球化学、地质微生物组学、地震地质综合解释多手段综合研究方法,探讨了其烃类气体的来源和成因机制。结果显示南海北部水合物气体的成因类型具有多元化特点,原生型、次生型微生物气和热解成因煤型气、油型气均有发现,不同水合物矿藏中热解成因气体遭受了不同强度的微生物降解改造作用:神狐W11-17矿藏>神狐W18-19矿藏>琼东南GMGS5-W08矿藏。水合物气源层由浅部微生物气源层(20~85℃)和深部热解成因气源层(镜质体反射率R_(o)>0.5%)组成,目前已钻遇的300 mbsf以浅的微生物气源层产气潜力相对较低,但热解成因气源由于具备一定规模的烃源灶和正处于成熟阶段的煤系烃源岩等条件而表现出较高的产气潜力。深部热解成因烃源灶、中部常规油气藏、浅部微生物气源层和复合型输导通道(控洼断裂、气烟囱、管状渗漏、微裂缝等)构成了南海北部高饱和度水合物矿藏的气源供给体系,深部热解气的贡献极为关键,但大部分热解气运移经过微生物气源层(20~85℃)时遭受了微生物次生改造,最后转化为次生型微生物甲烷为水合物成矿供源。南海北部高饱和度水合物矿藏中的烃类气体具有3种成因:一是从深部热解成因烃源灶直接运移而来,即未降解热解气;二是深部来源热解成因烃类运移至微生物气源层后经微生物厌氧降解产甲烷过程生成,即次生型微生物气;三是浅部微生物气源层中的微生物利用原地沉积物有机质直接生成,即原生型微生物�The origin of hydrocarbon gas is crucial for clarifying the formation and accumulation mechanisms of natural gas hydrate.Many highly saturated natural gas hydrate deposits have been drilled in the northern South China Sea.However,the source and genetic mechanism of hydrocarbon gases have not been systematically elucidated,significantly restricting the identification of main gas sources and the deployment of future exploration strategies.In this study,taking the typical highly saturated gas hydrate deposits in the Qiongdongnan and Shenhu areas as examples,the source and genetic mechanism of hydrocarbon gases are systematically investigated using an integrated approach that includes gas geochemistry,sediment organic geochemistry,geomicrobiology,and seismic interpretation.The results show that the genetic types of hydrate gases in the northern South China Sea are diverse,including primary and secondary microbial gases,as well as thermogenic coal-type and oil-type gases.Notably,the thermogenic gases within different gas hydrate deposits have undergone microbial degradation and modification to varying extents:Shenhu W11-17 gas hydrate deposit>Shenhu W18-19 gas hydrate deposit>Qiongdongnan GMGS5-W08 gas hydrate deposit.The hydrate gas source layer consists of a shallowly buried microbial gas source layer(2085℃)and a deeply buried thermogenic gas source layer(vitrinite reflectance R_(o)>0.5%).The upper part of the microbial gas source layer(<300 mbsf),which has been drilled and sampled,shows relatively low gas generative potential.In contrast,the thermogenic gas source represents great gas generative potential due to the existence of effective source kitchens and gas-prone coal-type source rocks in the mature stage.The deeply buried thermogenic source kitchen,conventional hydrocarbon deposits,shallowly buried microbial gas source layer,and composite gas migration conduits(including depression-controlled faults,gas chimneys,tubular seeps,and microfractures)constitute the hydrocarbon gas supply system for the highly sat

关 键 词：次生型微生物气 气体成因 气源供给体系 成藏过程 天然气水合物 

分 类 号：P618.13[天文地球—矿床学]