Based on systematic analysis of helium-rich gas reservoirs in China's major petroliferous basins， statistical assessment of their geochemical characteristics， and comprehensive synthesis of helium generation-migration-accumulation （GMA） processes， this study establishes a holistic geological framework for the entire GMA chain of helium-rich gas accumulations in China. This framework elucidates their spatial distribution patterns， fundamental formation prerequisites， associated geological-structural settings， and coupled enrichment mechanisms. Analysis reveals a distinct spatial trend wherein the host strata of helium-rich reservoirs become progressively older from east to west across China， with the majority concentrated at shallow depths （<4 500 m）. Geochemical characterization indicates that helium in these reservoirs is predominantly crustal-derived. Specifically， helium-rich reservoirs in central-western basins are primarily hydrocarbon-bearing with exclusively crustal-sourced helium， whereas those in eastern rift basins comprise three distinct types： helium-rich hydrocarbon gas， helium-rich CO2 gas， and helium-rich N2 gas reservoirs， all exhibiting mixed crustal-mantle helium origins. Investigation of GMA characteristics identifies U/Th-rich ancient granites/metamorphic rocks and organic-rich black shales as the primary crustal helium sources， while the source of mantle-derived helium is mantle-derived fluids. Helium migration relies on carrier phases （natural gas， active groundwater， mantle volatiles） and efficient conduit systems， notably deep-seated faults. Helium accumulation is governed by the volume of carrier gas charge， trap structural position， and preservation conditions. Ultimately， we propose that the formation and enrichment of helium-rich gas reservoirs result from the spatiotemporal coupling of three essential elements： sufficient helium supply， efficient transport systems， and favorable accumulation-preservation conditions. This integrated model provides the theoretical foundation for scientifically predicting prospective helium exploration zones in China.
Practical studies have revealed a close association between helium-rich natural gas and regional mudstone-shale formations. However， the controlling role of regional shales in helium enrichment remains underexplored. This paper analyzes the generation， migration and accumulation relationships between helium and four regional shale units in the Sichuan Basin： The Qiongzhusi Formation， Wufeng-Longmaxi formations， Dongyuemiao Member， and Da′anzhai Member of the Ziliujing Formation. Based on it， it can be concluded that： The cumulative helium generation intensity of these shales ranges from 0.57×10⁴ to 21.31×10⁴ m³/km²， exhibiting a pronounced vertical attenuation trend.This intensity is significantly weaker than the 43.62×10⁴ m³/km² generated by basement granites. Terrestrial shale hydrocarbon generation demonstrates a helium dilution capacity exceeding 43 901.7 times， surpassing that of marine shales. Notably， the Qiongzhusi Formation exhibits the weakest hydrocarbon dilution intensity （about 267.5 times）， below the typical dilution intensity of conventional source rocks （3 000 times）. At current geological conditions， the helium dissolution capacity in shale pore water is about 30 to 76 times the historical cumulative amount of geologic helium generation， driving pressure-driven directional migration and systematic accumulation of dissolved helium in confined aquifers. Gas-bearing shale layers establish a “dual deceleration zone” through capillary sealing and hydrocarbon diffusion retardation， effectively reducing vertical helium escape rates. Spatial helium distribution in the Sichuan Basin is dominantly controlled by the Qiongzhusi mudstone/shale， indicating that helium accumulation is primarily governed by the first regional shale unit overlying the principal helium source rock. Deep-seated faults intersecting basement helium sources facilitate deep helium expulsion， enabling shallow helium-rich gas reservoir formation.
This paper clarifies the helium sources and the controlling factors for the differences in helium enrichment in the Dengying Formation of the Weiyuan and Anyue gas fields through the geochemical characteristics of natural gas components， rare gas isotopes， and the proportion of water-soluble helium desorption. The results show that： （1） The average helium content in the Dengying Formation of the Weiyuan Gas Field is 0.25%， while that of the Anyue Gas Field is only 0.024%. （2） The mantle-derived helium contribution ratio in both gas fields is less than 1%， indicating a typical crustal source of helium. （3） The helium in the Dengying Formation of the Weiyuan Gas Field comes from the desorption of water-soluble helium in the basement granites， while in the Dengying Formation of the Anyue Gas Field， the helium in some wells with higher helium content （He > 0.04%） comes from the desorption of water-soluble helium in the basement metamorphic rocks， and the helium in wells with lower helium content mainly comes from the free helium in the Qiongzhusi Formation. （4） The different initial water-soluble helium concentrations in the two types of helium source rocks， granites and metamorphic rocks， are the main reasons for the differences in helium enrichment in the Dengying Formation of the two gas fields. The desorption of helium and the dilution effect of hydrocarbon gas injection during the tectonic uplift process are also the reasons for the further differences in helium enrichment in the Dengying Formation of the two regions. This study provides new ideas for the exploration of helium-rich reservoirs in ancient superimposed basins through analogy.
The Sichuan Basin is a favorable region for helium exploration， hosting multiple types of helium source rocks. However， the helium generation potential of different source rocks remains unclear. This study systematically evaluates the uranium and thorium content differences and helium generation potential of various lithologies using 99 helium source rock samples collected from the Sichuan Basin. The analyses include petrological examination， whole-rock major and trace element testing （XRF， ICP-MS）， zircon U-Pb dating （LA-ICP-MS）， and noble gas isotope analysis （heating-melting mass spectrometry）. The results indicate that： （1） Various types of helium source rocks are developed in the Sichuan Basin， with granites and mudstones/shales exhibiting higher uranium and thorium contents （U： 2.92×10-6， Th： 17.68×10-6）. Among them， granites， which are widely distributed within the basin， serve as the primary helium source. （2） Helium generation in the basement rocks of the Sichuan Basin is predominantly crust-derived. The helium content in granitic and metamorphic rocks varies with lithology and correlates with uranium and thorium concentrations. Gas within metamorphic rocks exhibits weak mantle-derived incorporation， presumably related to deep thermal flow. （3） Based on uranium and thorium content measurements， the average helium generation potential per unit mass of rock follows the order： mudstone/shale > granite > metamorphic rock > intermediate rock > mafic rock. This study clarifies the distribution of helium source rocks in the Sichuan Basin and its surrounding areas， providing essential data for further assessments of helium generation potential and resource estimation. The findings offer valuable insights for future helium exploration in the region.
Previous studies have discovered helium resources in the coalbed gases of the Carboniferous–Permian coal-bearing strata in areas such as Baode， Sanjiaobei-Shixi， Daning-Jixian， and Hancheng at the eastern margin of the Ordos Basin. Gas component analysis results have shown significant regional differences in the concentration of helium in coalbed gas. This paper conducts a comprehensive geological study to analyze the key geological controlling factors responsible for the differential enrichment of helium in the coalbed gases at the eastern Ordos Basin. Geochemical analysis indicates that most Carboniferous-Permian coal-bearing rocks in the Ordos Basin have high Th-U contents and helium generation potential. However， due to the generally high content of hydrocarbon gases in coal seams， indigenous 4He generated by in-situ decay of coal-bearing rocks without external helium supplementation is unable to form helium resources of industrial value. Baode， Sanjiaobei–Shixi， and Daning-Jixian are located in the Jinxi flexure zone with similar structural deformations， but only in the Sanjiaobei-Shixi region does the concentration of helium in coalbed gas reach industrial extraction standards， a variability possibly linked to the basement. Aeromagnetic data reveal that the Sanjiaobei-Shixi region is situated above basement gneiss rock， which has undergone prolonged decay and exhibits a high helium generation potential， serving as an important supply source of helium in the Carboniferous-Permian coalbed gases in the region. Similar to the Sanjiaobei-Shixi region， the Hancheng mining area also lies above gneiss basement rock， but the helium content in coalbed gas in the Hancheng region is significantly lower than that in the Sanjiaobei region. Seismic profiles and field observations indicate that significant deep-seated faults cutting through the Carboniferous-Permian strata are not developed in the Sanjiaobei-Shixi region， while the Hancheng region features prominent deep-seated faults， causing intense tectonic deformation and structural damage to the Carboniferous-Permian coal-bearing strata in the area. This paper proposes that the supply of external helium sources such as basement gneiss is the basis for the enrichment of helium in coalbed gas， and that later tectonic processes are essential for the modification of coal-bearing strata to ensure the enrichment of helium in coalbed gases. Later tectonic modifications should facilitate the transportation of external helium sources to the coal-bearing strata while ensuring efficient retention of helium.
In recent years， research on helium in onshore gas reservoirs has received increasing attention both domestically and internationally， but there is relatively little research on the genesis and accumulation of helium in offshore oil and gas reservoirs. By summarizing and analyzing the helium content in oil and gas reservoirs， helium isotope ratio， associated geochemical characteristics of carbon dioxide in the Pearl River Mouth Basin， this paper discussed the origin of helium in the Pearl River Mouth Basin， and summarizes the helium accumulation model of typical high- to rich-helium gas reservoirs in this region. The research shows that the helium content of dissolved gas in the CO2 gas cap oil layer in Enping 15-A Oilfield in the Pearl River Mouth Basin is 0.227%- 0.725%， reaching the helium-rich level. The helium content of CO2 gas reservoir in Enping 23-E Oilfield is 0.101%， reaching the helium-high level. The helium contents of other oil and gas fields are lower than 0.03%， which are helium-poor to helium-low reservoirs. Oil and gas reservoirs with high He content in the Pearl River Mouth Basin are generally rich in CO2， and He may be associated with CO2. The values of 3He/4He are all in the range of （0.82-11.42）×10-6， showing characteristics dominated by mantle derived factors for typical high- and rich-helium oil and gas reservoirs. Through the analysis of diagenetic sequence of oil and gas inclusions in high- to rich-helium oil and gas reservoirs and microthermometry data， it is believed that the oil and gas charging characteristics of the Zhujiang Formation in helium-rich Enping 15-A Oilfield and the Enping Formation in Enping 23-E Oilfield CO2 gas reservoir are “two phases of oil， two phases of CO2 and associated helium”. Volcanic activity and deep faults control the accumulation of CO2 and helium， and two helium accumulation models have been established： deep faults to structural ridges to shallow reservoirs of the Zhujiang Formation； the controlling faults communicating with volcanic activity zones to shallow faults or volcanic vents to deep reservoirs of the Enping Formation. For the Pearl River Mouth Basin， where deep faults and tectono magmatic activities are developed， is a favorable area for the discovery of helium rich resources.
Helium （He） is an indispensable strategic resource in high-tech industries， and its migration and preservation are highly dependent on the synergistic effects of carrier gases such as methane （CH₄）， carbon dioxide （CO₂）， and nitrogen （N₂）. To elucidate the microscopic coupling mechanisms and environmental dependence of He-carrier gas interactions， this study integrates quantum chemical calculations with molecular configuration screening to systematically evaluate the coupling energies and structural stability of He with various carrier molecules under both anhydrous and hydrous conditions. The results show that in anhydrous environments， the coupling affinity of He follows the order CO₂ > CH₄ > N₂ > He. Under hydrous conditions， the affinity of He for CO₂ and CH₄ decreases， while its interaction with N₂ becomes significantly more stable， accompanied by notable spatial relocation of the coupling sites. Solvation effects from water molecules enhance the He-N₂ interaction，indicating that pore water can promote the co-existence of He and N₂. In multi-molecular systems， He-H₂O complexes exhibit the highest stability， followed by He-CO₂， He-CH₄， and He-N₂. In addition， carrier molecules， due to their larger molecular sizes and the formation of molecular clusters， can cause physical obstruction in caprock pore throats， thereby improving sealing capacity and reducing He leakage. Based on these findings， this study identifies three critical microscopic contributions of carrier gases to helium accumulation， summarized as “aggregation in water， transport through fractures， and retention by caprock.” These mechanisms reveal， from a molecular perspective， the cooperative role of the He-carrier system in helium accumulation， providing a theoretical foundation for understanding accumulation mechanisms， evaluating caprock sealing efficiency， and predicting helium-rich sweet spots.
Natural hydrogen as a kind of clean energy will occupy an important position in the future energy pattern， many countries and regions in the world have carried out natural hydrogen exploration and research in different geological environments. At present， there are few related works in the field of natural hydrogen in China. In order to discuss the field and development direction of natural hydrogen exploration， this study analyzed the practical results of natural hydrogen investigation in China and the research on reservoir formation mechanism from the perspective of hydrogen system. Based on geotectonic conditions， groundwater occurrence characteristics， hydrogen source rock types and spatial and temporal distribution， the future natural hydrogen exploration potential areas in China are predicted and evaluated. The conclusions are as follows： （1） Abnormal hydrogen content has been detected in many sedimentary basins in China， with the highest concentration of 99%. Certain hydrogen content has also been found in other geological environments such as fault zones. The hydrogen is characterized by mixed sources. （2） There are various types of hydrogen source rocks in China， including ophiolite， banded iron formation （BIF）， basalt， granite and uranium ore， and they have spatial and temporal distribution characteristics. The deep faults outside the basin may release hydrogen from deep. The faults in the basin not only communicate hydrogen source and reservoir， but also form structural traps. Hydrogen-bearing reservoirs include shale， sandstone， coal and other lithologies， and their porosity and permeability characteristics are quite different. （3） Based on the comprehensive evaluation of hydrogen source rock association and groundwater conditions， it is divided into five areas， such as North China， Northeast and Northwest. Songliao Basin， Bohai Bay Basin and Junggar Basin. There are natural hydrogen prospect areas in Songliao Basin， Bohai Bay Basin， Junggar Basin and its surroundings. The natural hydrogen of ophiolite type represented by Tibet has exploration potential. It is believed that the compound superposition effect of multi-age and multi-type hydrogen source rocks and the underground water-bearing area are the important geological conditions for the formation of high content of natural hydrogen， and the influence of faults and formation rock characteristics on the occurrence of natural hydrogen should be considered in practical work.
As a clean energy source， hydrogen plays a significant role in the global energy transition. Natural hydrogen resources are widely distributed on Earth. Based on a comprehensive review of the genesis mechanisms and distribution patterns of globally discovered natural hydrogen， this paper categorizes the sources of natural hydrogen into two main types： organic and inorganic. The organic sources include microbial activity and organic matter pyrolysis， while the inorganic sources encompass various types such as deep hydrogen， water-rock reactions， Precambrian trapped hydrogen， radiogenic origins， fault activation， and Magma degassing. Given the current research status of natural hydrogen and the geological conditions of hydrogen-rich reservoirs， China's natural hydrogen resources have vast exploration prospects and significant potential. Due to the reactive chemical nature and complex formation mechanisms of natural hydrogen， research on its sources， migration， and accumulation mechanisms requires comprehensive analysis， incorporating characteristics of associated gases.
Against the backdrop of global efforts to address the climate crisis and the third energy structural transformation， an increasing number of countries are strategically formulating energy-saving and emission-reduction plans to reduce the production of fossil fuels such as petroleum and coal. Natural hydrogen gas， as a green and low-carbon energy source， with its high calorific value and absence of combustion pollution， has attracted attention worldwide. This paper systematically reviews the genesis mechanisms， distribution characteristics， and enrichment mechanisms of high-content （greater than 10%） natural hydrogen gas globally. The study reveals： （1） The genesis types of natural hydrogen gas are complex and diverse， and can be classified into two major categories based on their reaction mechanisms： organic genesis and inorganic genesis. Pyrolysis of organic matter， deep earth degassing and water-rock reaction are the main mechanisms of natural hydrogen generation， while biological processes and radiolysis of water play an auxiliary role in hydrogen enrichment in some specific environments. （2） The distribution range of natural hydrogen with high content is wide in the world. By comparing the formation and enrichment laws of hydrogen in different geological and tectonic environments around the world， it is found that natural hydrogen gas reservoirs with high content can exist in intra-continental rift system， Precambrian system， plate collision zone， subduction zone and their peripheral locations. （3） High-quality hydrogen source is the basis of hydrogen enrichment， and favorable migration， accumulation and preservation conditions are the key to hydrogen accumulation. Based on the concept of “source-migration-reservoir caprock” in traditional hydrocarbon accumulation theory， the dynamic accumulation model of natural hydrogen is proposed， and the formation and evolution process of underground natural hydrogen as well as the accumulation and preservation mechanism are discussed. （4） On the basis of in-depth analysis of the genetic mechanism and enrichment mechanism of natural hydrogen， the energy significance and future development trend of natural hydrogen are pointed out， in order to provide reference for promoting the transition from high carbon to low carbon and no carbon energy in the energy field.
Kerogen of source rock has great potential for hydrogen production during thermal maturation evolution. At present， the characteristics of hydrogen production during the thermal evolution of kerogen are unclear， the influence mechanisms of chemical structure and pore structure of kerogen on the hydrogen production capacity are unknown， and the mechanisms of the role of water on the pyrolytic hydrogen production of kerogen need to be elucidated. In this work， the unit structures and matrix models of kerogen under dry and water-bearing conditions were constructed， and the molecular dynamics simulation method based on the ReaxFF force field was used to conduct the pyrolysis simulation of immature kerogen at elevated temperatures and kerogen at different maturity stages. The results show that： （1） During the thermal maturation process， the lower matured kerogen is more capable of producing hydrogen， and hydrogen is mainly produced in the high-temperature stage； （2） The main mode of hydrogen production during kerogen thermal evolution is the combination of hydrogen atoms from the aliphatic structures； （3） Water promotes the pyrolysis of hydrogen in the aliphatic structure of kerogen through the role of hydrogen source and the catalytic effect； （4） Hydrogen production from thermal evolution of kerogen is affected by both chemical structure and pore structure， with chemical structure having a greater influence than pore structure. The results improve the theory of hydrogen production from pyrolysis of kerogen， which can provide theoretical guidance for the exploration and development of natural hydrogen reservoirs.
Hydrogen energy serves as an ideal zero-carbon alternative to fossil fuels. With increasing global demand for hydrogen energy， natural hydrogen has become an international research focus due to its low-carbon characteristics and economic advantages. The Qaidam Basin， a typical sedimentary basin with abundant natural gas resources， possesses unique geological conditions favorable for hydrogen generation， demonstrating significant potential for natural hydrogen accumulation. This study investigates the geochemical characteristics and formation mechanisms of natural hydrogen in the Altun Piedmont zone through analysis of hydrogen content and isotopic composition in natural gas samples. Results show that the Dongping gas field contains relatively high hydrogen concentrations （3.349%）， while the Niudong and Jianbei gas fields exhibit lower values （0.008% and 0.113%， respectively）. The δ²H values range from -799.6‰ to -722.5‰. Geochemical analysis of natural gas components indicates that the hydrogen in this region is primarily of inorganic origin. Combined with helium isotope analysis and regional geological setting， we propose that water-rock reactions constitute the main formation mechanism， where radioactive decay in granitic basement generates both helium and hydrogen， which subsequently accumulate along deep fault zones. These findings provide a theoretical foundation for natural hydrogen exploration in the Qaidam Basin and similar geological settings.
Amid the global transition to low-carbon energy systems， hydrogen energy， as a zero-carbon energy carrier， relies on underground hydrogen storage （UHS） technology for large-scale storage. This paper systematically reviews research progress on hydrogen diffusion mechanisms in UHS systems， focusing on multi-mechanism coupled diffusion theory in porous media， innovations in experimental testing methods， and cross-scale numerical simulations. The study reveals that hydrogen diffusion involves synergistic mechanisms of Fick diffusion， Knudsen diffusion， and surface diffusion. Knudsen diffusion contributes 60%-85% to mass transfer in nanopores， while surface diffusion significantly influences transport efficiency in organic/clay-rich media. Experimental findings indicate that rock type （e.g.， salt rock diffusion coefficients： 10⁻¹¹-10⁻⁹ m²/s； shale： 10⁻¹⁰- 10⁻⁸ m²/s）， pore structure， temperature-pressure conditions （a 40 °C temperature rise can increase diffusion coefficients by over 50%）， and pore water properties （5%（wt） salinity increase reduces diffusion coefficients by 12%-30%） are critical factors governing diffusion behavior. However， existing experimental methods （e.g.， hydrocarbon concentration method， desorption method） exhibit data variability spanning two orders of magnitude under high-temperature and high-pressure conditions （>100 °C，>30 MPa）. Numerical simulations remain limited in modeling multi-field coupling （thermal-hydraulic-chemical-mechanical interactions） and microbial effects. Future research should prioritize cross-scale model development， high-temperature/high-pressure in situ experimental techniques， multi-physics coupled simulations， and long-term stability assessment frameworks. Establishing standardized testing protocols and intelligent digital twin platforms will enhance the safety and efficiency optimization of UHS engineering， providing crucial theoretical support for hydrogen energy infrastructure development.
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