Formation mechanism of deep natural hydrogen in the Sichuan Basin  

作　　者：Xiaomei WANG Kun HE Chunlong YANG Hao XIE Xiaobo WANG Yitong LYU Linfeng XIE Shuichang ZHANG 

机构地区：[1]Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China [2]Key Laboratory of Petroleum Geochemistry,China National Petroleum Corporation,Beijing 100083,China [3]International Center for Isotope Effects Research,School of Earth Science and Engineering,Nanjing University,Nanjing 210023,China

出　　处：《Science China Earth Sciences》2025年第2期581-597,共17页中国科学(地球科学英文版)

基　　金：supported by the National Key Research and Development Program of China(Grant No.2022YFF0800304);the Science and Technology Project of China National Petroleum Corporation(Grant No.2024DJ93);the Basic Research and Strategic Reserve Technology Research Project of China National Petroleum Corporation(Grant No.2020D-5008-01)。

摘　　要：As a potential renewable and clean energy source,the distribution and exploration prospects of natural hydrogen have garnered widespread attention.However,the limitations in understanding the formation mechanisms and accumulation patterns of underground natural hydrogen have significantly constrained its efficient exploration and utilization.This study reports H_(2)content and isotopes in natural gas from deep formations in sedimentary basins through geochemical analysis of 58 conventional gas samples from the Sinian to Triassic strata in the central Sichuan Basin.We discovered that H_(2)content in deep natural gas in central Sichuan generally exceeds 0.1%,with a maximum of 1.6%,and hydrogen isotopes(δ^(2)H_(H_(2)))range from-850‰to-586‰.Analysis of the geological conditions,hydrogen generation mechanisms,and isotope fractionation characteristics in the study area confirms that microbial fermentation or in-situ organic matter cracking are not effective pathways for deep H_(2)generation.Combined with helium content and isotope analysis of the natural gas,it is inferred that the volcanic basement in the central Sichuan area is the potential source rock for natural H_(2)in the Sinian to Triassic strata.Specifically,H_(2)originates from the radiolysis of water and hydrothermal reactions of Fe(Ⅱ)in the basement granite.Additionally,a diffusion fractionation model reveals significant isotope fractionation during the migration and accumulation of deep H_(2)into sedimentary reservoirs,which lead to anomalously light δ^(2)H_(H_(2))in deep natural gas in central Sichuan.This indicates that the underground natural hydrogen accumulation is in a long-term dynamic process,with simultaneous H_(2)accumulation and dissipation in the gas reservoirs.This research not only elucidates the formation mechanism of deep H_(2)but also provides insights for the resource potential of natural hydrogen in sedimentary basins.

关 键 词：Natural H2 Sichuan Basin Hydrogen generation mechanism Isotope fractionation 

分 类 号：P61[天文地球—矿床学]