琼东南盆地深水区浅表层水合物稀有气体地球化学特征及意义  

Noble gas geochemical characteristics of shallow hydrate in the deep water of the Qiongdongnan Basin and their significance

作　　者：孙涛 吴涛 葛阳 樊奇 李丽霞 吕鑫 SUN Tao;WU Tao;GE Yang;FAN Qi;LI Lixia;LÜXin(CNOOC Research Institute Ltd.,Beijing 100028,China;State Key Laboratory of Natural Gas Hydrates,Beijing 100028,China;CNOOC China Ltd.,Haikou 570100,China)

机构地区：[1]中海油研究总院有限责任公司,北京100028 [2]天然气水合物国家重点实验室,北京100028 [3]中海石油(中国)有限公司海南分公司,海南海口570100

出　　处：《地学前缘》2022年第5期476-482,共7页Earth Science Frontiers

基　　金：国家重点研发计划项目(2016YFC0304000);国家自然科学基金项目(U19B2005)。

摘　　要：琼东南盆地深水区具备形成天然气水合物藏的地质条件,是我国海洋天然气水合物两个勘探开发先导示范区之一。本文选取深水区浅表层水合物为研究对象,基于天然气地球化学、稀有气体地球化学分析,开展了其与深部常规天然气藏的对比研究。结果表明:本次研究的浅表层气体碳同位素与深部常规天然气碳同位素的特征类似,气源主要为深部热成因气,生物气的贡献不明显,气体的成因类型为煤型气,推测气源岩为崖城组煤系烃源岩。轻稀有气体Ar同位素组成显示,气源岩和第三系相关;样品中^(3)He/^(4)He值偏高,指示了部分幔源气的贡献。因此,在富生烃凹陷背景下,讨论深部热成因气对水合物成藏具有重要意义,深部热成因气藏与浅层水合物藏在垂向上可以形成立体的天然气藏,为未来的“多气可采”提供理论支持,也有助于提高深水区天然气水合物矿藏开发的经济性。The deep water area of the Qiongdongnan Basin possesses favorable geological condition for gas hydrate accumulation and is one of the leading demonstration areas for marine gas hydrate exploration and development.Based on geochemical analyses of natural gas and noble gases,this paper selects the shallow surface hydrate of the deep water area to carry out a comparative study relating to deep conventional natural gas reservoirs.The results show that shallow surface gas in the study area shares similar carbon isotope characteristics with deep conventional natural gas.The gas source is mainly deep thermogenic gas,with no obvious contribution from biogas,and genetically relates to coal-type gas.It is speculated that the gas source is the coal measure strata of the Yacheng Formation.The Ar isotopic compositions of light noble gases show that the gas source rock is related to the Tertiary formation,whilst the high ^(3)He/^(4)He ratios in samples indicate certain contributions from mantle derived gas.Therefore,under the background of gas-rich depression,it is of great significance to discuss the deep thermogenic gas for hydrate accumulation.The deep thermogenic gas reservoir and shallow hydrate reservoir can form a vertical three-dimensional gas reservoir,which lends theoretical support in future“multi-gas exploitation”for improving economic benefits of gas hydrate reservoir development in deep water areas.

关 键 词：琼东南盆地 天然气水合物 气源 煤型气 稀有气体 

分 类 号：P744.4[天文地球—海洋科学] P736.2