地质体中天然氢气成因识别方法初探

氢气作为一种清洁能源，已得到国内外越来越多的重视。近年我国加快氢能经济建设，对氢气的生产与储存提出了较高的要求。目前氢气的主要获取方式为人工制取氢气。了解自然界中是否存在高含量氢气，其成因如何，是能否发现并利用天然氢气的前提所在，但能否持续获得天然氢气，目前研究较弱。对氢气成因的判别，特别是深源成因与浅源成因主要依靠伴生稀有气体同位素组成特征进行判断，而部分天然气难以测定稀有气体，给氢气成因识别带来了困难。基于不同构造部位氢气及伴生气的含量、同位素组成等分析测试结果，分析美国堪萨斯(Kansas)盆地高含量氢气的持续时间和含量变化特征。并提出了基于甲烷—氢气含量关系与氢气氢同位素组成的氢气成因判别方法，降低了氢气成因识别的难度。认为地下条件下存在氢气补充机制，可以持续获得高含量天然氢气，板块碰撞带周边是高含量氢气的有利分布区。可以以氢气的氢同位素组成-700‰(VSMOW)和ln (CH₄/H₂)值划分氢气来源：壳源氢气的δD值一般大于-700‰，而ln (CH₄/H₂)值小于-8；幔源氢气的δD值一般小于-700‰，而ln (CH₄/H₂)值大于-4；富CO₂流体在地表被氧化后剩余的氢气，其δD值大于-700‰，而ln (CH₄/H₂)值大于-8；深源富氢流体在地表被氧化后，剩余氢气的δD值小于-700‰，而ln (CH₄/H₂)值小于-4。该方法可以在不测定稀有气体组分及同位素组成的条件下，对氢气成因进行快速分类。

Identification method for the origin of natural hydrogen gas in geological bodies

As one of the clean energies, hydrogen has attracted more and more global research interest. With the acceleration of hydrogen energy economic construction in China, higher requirements have been put forward for the production and storage of hydrogen. At present, the main way to obtain hydrogen is to produce hydrogen artificially. Whether there is a high content of hydrogen in nature and its origin are the premise for the discovery and utilization of natural hydrogen, but the related research is weak. The discrimination of hydrogen origin, especially deep and shallow source origin, depends mainly on the isotopic composition characteristics of accompanied rare gases, which is difficult to be determined in some cases, the origin of hydrogen is then difficult to be identified. Based on the analysis and analytical results of hydrogen and associated gas content and isotopic composition in different structural parts, this paper analyzes the duration and content variation characteristics of high content hydrogen in the Kansas Basin, USA. A discrimination method for hydrogen genesis based on the relationship between methane and hydrogen content and hydrogen isotopic composition has been proposed, access of hydrogen genesis identification is easier to be achieved. Based on the above research, it is believed that there is a hydrogen supplement mechanism with underground conditions, which can continuously produce high content of natural hydrogen. It is considered that it is a favorable distribution area for high content of hydrogen around the plate collision zone. The hydrogen source can be classified by the hydrogen isotopic composition of -700‰ (VSMOW) and ln(CH₄/H₂). Shell source hydrogen has a δD value generally greater than -700‰ and a ln(CH₄/H₂) value lower than -8. Mantle derived hydrogen has a δD value generally lower than -700‰ and a ln(CH₄/H₂) value greater than -4. Hydrogen remaining after CO₂ rich fluid is oxidized on the surface has a δD value greater than -700‰ and a ln(CH₄/H₂) value greater than -8. After the deep source hydrogen rich fluid is oxidized on the surface, the residual hydrogen has a δD value lower than -700 ‰ and a ln(CH₄/H₂) value under -4. This proposed method can quickly classify the origin of hydrogen without determining the composition and isotopic composition of rare gases.