南海琼东南盆地两种不同成因天然气水合物赋存的深层沉积物地球化学特征对比  

Comparison of geochemical characteristics of natural gas hydrate-related sediments in Qiongdongnan Basin,South China Sea

作　　者：王俊杰 蒋彬[1,2,4] 廖玉宏 赖洪飞[3,5] 郭睿波 曾清 黄越义 方允鑫 匡增桂 WANG Junjie;JIANG Bin;LIAO Yuhong;LAI Hongfei;GUO Ruibo;ZENG Qing;HUANG Yueyi;FANG Yunxin;KUANG Zenggui(State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou 510760,Guangdong,China)

机构地区：[1]中国科学院广州地球化学研究所,有机地球化学国家重点实验室,广东广州510640 [2]中国科学院深地科学卓越创新中心,广东广州510640 [3]南方海洋科学与工程广东省实验室(广州),广东广州511458 [4]中国科学院大学,北京100049 [5]中国地质调查局广州海洋地质调查局,广东广州510760

出　　处：《地球化学》2023年第2期180-190,共11页Geochimica

基　　金：国家自然科学基金项目(41803042、41872156);中国科学院战略性先导科技专项(A类)(XDA14010103);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0102);中国地质调查局地质调查项目(DD20190230)联合资助。

摘　　要：对来自琼东南盆地W03和W09站位的天然气水合物分解气及其赋存沉积物的地球化学特征进行对比研究。结果表明, W03和W09站位的天然气水合物分解气分别对应以生物气为主和以热成因气为主的混合成因气, 2个站位水合物赋存的深层沉积物的地球化学特征具有显著差异。以生物成因气为主的W03站位沉积物表现出较高的总有机碳(TOC)、较低的硫酸盐含量以及较高的孔隙度,这些是产甲烷菌活跃的有利条件;同时天然气水合物富集层沉积物的饱和烃中显示出强度很高的低碳数未分离复杂化合物(UCM)鼓包(C_(12)~C_(19)),推测该站位沉积物中产甲烷菌活跃。以热成因气为主的W09站位沉积物中轻重烷烃指数(L/H)、姥鲛烷/植烷(Pr/Ph)和n-C_(17)/Pr等多种生物标志物特征表明,该站位在天然气水合物富集层有明显的油源烃浸染的痕迹,推测来自深部油气藏的天然气将油源烃携带到天然气水合物层位,同时该站位部分样品色谱图中显示出与油源烃微生物降解活动相关的UCM鼓包(C_(17)~C_(21)),表明油源烃在沉积物中也受到了微生物降解活动的影响。We evaluated the geochemical characteristics of decomposed gas and its accompanying sediments from the W03 and W09 stations in the Qiongdongnan Basin.The results showed that W03 and W09 correspond to two types of mixed gas,mainly biogenic gas and thermogenic gas.The geochemical characteristics of the deep sediments accompanied by hydrates and the two stations significantly differed.The biogenic gas dominating sediments at the W03 site showed a high total organic carbon,low sulfate content,and high porosity,which are favorable conditions for methanogen activity.Compared with gas hydrate-free deposits from adjacent boreholes,the gas hydrate-enriched deposits showed a high intensity of unresolved complex mixture(UCM)bulge(C_(12) to C_(19))in the saturated hydrocarbons chromatogram.This result indicates the existence of traces of microbial modification,and that the sediments at the station are suitable for methanogen activity.A large amount of biogas was produced,and a gas hydrate-rich area was formed.However,L/H,Pr/Ph and n-C_(17)/Pr in the sediments of the W09 station,which is dominated by thermal gas,indicate that there are obvious traces of oil-source hydrocarbon impregnation in the gas hydrate enrichment layer at this station.Gas from the deep reservoir may have carried the oil-source hydrocarbon to the gas hydrate horizon.Additionally,the chromatograms of some samples at the station showed UCM bulges(C_(17) to C_(21))related to microbial degradation of oil-derived hydrocarbons,indicating that oil-derived hydrocarbons were affected by microbial degradation in the sediments.

关 键 词：天然气水合物 热成因气 生物成因气 UCM鼓包 琼东南 

分 类 号：P593[天文地球—地球化学]