《佳文速递》2025年第8期

Mechanism whereby Sediment Properties Control Gas Hydrate Accumulation in Fine-Grained Sediments

沉积物特性控制细粒沉积物中气体水合物聚集的机制

发表时间：2025年7月11日

发表期刊：《Energy&Fuels》

Chenyang Bai1,2,3, Pibo Su4,5,6, Yu Zhang3, Xiaolei Xu3, and Shujun Han7

1 Key Laboratory of Marine Mineral Resources and Polar Geology, Ministry of Education, China University of Geosciences (Beijing), Beijing 100083, China

2 Laboratory for Marine Mineral Resources, Laoshan Laboratory, Qingdao 266237,China;

3 School of Ocean Sciences, China University of Geosciences (Beijing), Beijing 100083, China

4 Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou S1007S, China;

5 National Engineering Research Center for Gas Hydrate Exploration and Development, Guangzhou Sll458, China;

6 Sanya South China Sea Institute of Geology, Guangzhou Marine Geological Survey, Sanya S7202S,China

7 Research Institute of Petroleum Exploration & Development, Beijing 100083, China

Abstract: Gas hydrates are mostly concentrated in silt–clay sediments, and the sediment properties (including the particle size and mineral composition) play an important role in controlling gas hydrate accumulation. The northern part of the South China Sea (SCS) is one of the most representative areas with fine-grained gas hydrate reservoirs. In this study, the particle size and mineral composition of 597 sediment samples from gas hydrate reservoirs and adjacent layers at seven sites in the Dongsha, Shenhu, and Qiongdongnan areas, northern SCS, were analyzed, and the sediment properties of the fine-grained gas hydrate reservoirs were determined. Specific surface area and irreducible water saturation analyses were conducted to reveal the controlling significance of the sediment properties on the accumulation of gas hydrates in the fine-grained sediments. The results show that the mineral composition has a controlling effect on the gas hydrate reservoirs and nongas hydrate layers. Due to the adsorption and constraint of illite and smectite mixed layers (I/S) on the gas and fluid and the complex microstructure of I/S, the gas hydrate reservoirs have low I/S and high felsic mineral contents. The sediment particle size has a significant controlling effect on the gas hydrate saturation and morphology in the fine-grained reservoirs. Dispersed low saturation gas hydrates are mainly formed via pore filling, and they appear in the gas hydrate reservoirs dominated by >16μm sediment particles. Visible high saturation gas hydrates are mainly formed via particle displacement, and they appear in the gas hydrate reservoirs dominated by <8μm sediment particles. The results of this study are helpful for further revealing the law of gas hydrate enrichment in fine-grained sediments and have important significance for gas hydrate exploration and development and its environmental effects.

Fig. 11. Pattern of gas hydrate enrichment in fine-grained sediments. (a) Macroscopic pattern of gas hydrate accumulation in fine-grained sediments; (b) microscopic pattern of gas hydrate enrichment in a deep reservoir; (c) sediment samples from the shallow gas hydrate reservoir at site QDN-W01-19 (5.5mbsf) showing the development of microcracks; (d) microscopic pattern of pore-filling gas hydrate formation; (e) microscopic pattern of particle displacement gas hydrate formation; (f) site SH-W19-15, where deep gas hydrate reservoirs have sediment and dispersed hydrate samples; (g) site DS-W08-13, where deep gas hydrate reservoirs have sediment and vein-like gas hydrate samples (71.23mbsf). 

https://doi.org/10.1021/acs.energyfuels.5c02384

Gas Phase Permeability of CO2 Hydrate-Bearing Silty-Clayey Sediments

含二氧化碳水合物的淤泥-黏土沉积物的气相渗透性

发表时间：2025年7月12日

发表期刊：《Energy&Fuels》

Chaozheng Ma1, Xiaoxu Hu2, Hongxiang Si2, Tingting Luo1, Juntao Pan1, Tao Han1, Yiming Zhu3, Weihao Yang1, and Yongchen Song4

1 State Key Laboratory of Intelligent Construction and Healthy Operation & Maintenance of Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, PR China

2 Xinwen Mining Group Co. Ltd, Taian 271233, China

3 School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China

4 Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, PR China

Abstract: Hydrate-based CO2 sequestration (HBCS) in marine sediments is an effective method for mitigating global climate change driven by energy consumption. The permeability characteristics of the CO2 hydrate-bearing sediments are key indicators for evaluating injection rates and reservoir sealing integrity. As the primary low-permeability lithology in marine sediments, silty-clayey sediments provide superior sealing integrity. However, the relative research on gas phase permeability of CO2 hydrate-bearing silty-clayey sediments still remains limited. Thus, a bespoke seepage experiment platform was independently developed in this study, and the effects of hydrate saturation and effective axial stress on the permeability evolution of CO2 hydrate-bearing silty-clayey sediment as well as the impact on sediment permeability caused by hydrate formation and dissociation were examined. The results indicate that increasing initial water saturation raises the resistance of sediments to CO2 gas flow, which is also influenced by CO2 dissolution and adsorption. In silty-clayey sediments, increasing water saturation from 10% to 35% results in a substantial reduction in gas phase permeability─by approximately 79.69%. In contrast to sandy sediments, the gas phase permeability of CO2 hydrate-bearing silty-clayey sediments exhibits a nonlinear trend with increasing hydrate saturation─initially rising, then declining, and subsequently increasing again. Axial stress compresses the pore space and throat size of silty-clayey sediments, resulting in a reduced gas phase permeability. At a hydrate saturation of 24.96%, the permeability of silty-clayey sediments under an effective axial stress of 3MPa is reduced by approximately 94.72% compared to that of unconsolidated sediments. In addition, hydrate dissociation leads to a reduction in sediment permeability, and this reduction becomes more pronounced as the hydrate saturation rises.

Fig.7. CO2 flow mechanisms in silty-clayey sediments. 

https://doi.org/10.1021/acs.energyfuels.5c02585

Characterizing methane hydrate phase transitions and multiphase flow behavior in porous media: Insights from low-field nuclear magnetic resonance measurements

描述多孔介质中的甲烷水合物相变和多相流行为：低场核磁共振测量的启示

发表时间：2025年7月16日

发表期刊：《International Journal of Heat and Mass Transfer》

Huiru Suna,b, Jing Chena, Xinhang Yanga, Pathegama Gamage Ranjithb, Yongchen Songa, Bingbing Chena, Mingjun Yanga

a Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, China 

b Deep Earth Energy Laboratory, Department of Civil and Environmental Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia

Abstract: Methane hydrate was viewed as a potential clean energy resource and has attracted extensive research attention in the energy field. The hydrate exploiting phase transition has complex characteristics, which was generally a coupling process of temperature, pressure, and multiphase flow field in reservoir. It is necessary to reveal the effect of reservoir environment on high-efficient exploitation of hydrate. In this study, a nuclear magnetic resonance (NMR) experimental system was used to analyze the phase transition characteristics of methane hydrate under different conditions (constant pressure, gas migration, and gas-water flow). The water migration behavior and water distribution evolution were also investigated in the hydrate-free and hydrate-bearing reservoir during the gas-water flow process. The findings showed that methane hydrate formation under gas migration and constant pressure conditions was divided into three stages, included the hydrate nucleation induction, mass growth, and stabilization. Compared to constant pressure condition, gas migration resulted in a shorter induction time for hydrate formation. Additionally, the water distribution difference between hydrate-free and hydrate-bearing sediments was revealed. In the hydrate-bearing reservoir, hydrate phase transition induced the uneven water distribution, while the even distribution of free water was observed in the hydrate-free reservoir. Furthermore, water phase flow rate was confirmed the one of the key factors for promoting hydrate decomposition. A threefold increase in water phase flow rate led to an 80% increase in the hydrate decomposition rate. These results provided valuable insights for the efficient extraction of methane hydrates in natural reservoir.

Keywords: Methane hydrate; Multiphase flow; Formation and decomposition characteristics; Gas-water flow rate; Nuclear magnetic resonance

Fig. 2. Gas-water ffow characteristics in hydrate-free bearing sediment: (a) evolution of water distribution proffles; (b) variation of water saturation in different layers; (c) T2 relaxation time. 

https://doi.org/10.1016/j.ijheatmasstransfer.2025.127542.

Water distribution in case 4 of CO2 hydrate formation. (Micropore: T230 ms.) CO2Hydrate Sequestration in Unsealed Submarine Sediments: A 4D Pore-Scale Experimental Investigation

二氧化碳水合物形成情况4中的水分布。(微孔：T230 ms）： 4D孔隙尺度实验研究

发表时间：2025年7月13日

发表期刊：《Gas Science and Engineering》

Yanfang Lil,2, Tong Zhang1,2,3, Liang Yuan1,2, Ming Tang1,2,4,5, Ruilong Li1,2,Yongqiang Chen4,5, Wen Luo6, Chuanjiu Zhang6

1 School of Energy and Safety, State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and Technology

2 Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining

3.Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, University of Mining and Technology (Beijing)

4 Energy BU, CSIRO, Kensington, 6151, WA, Australia

5 Permanent Carbon Locking Future Science Platform, CSIRO, Australia

6 National energy Shendong Coal Group Co., LTD

Abstract: CO2 hydrate sequestration in marine sediments has been identified as a safe, large-scale, long-term carbon removal method. Influenced by the high pressure and low temperature, the dynamic formation of CO2 hydrate has not been fully investigated. We thus design and construct a low-field nuclear magnetic resonance (LF-NMR) facility to investigate the in-situ dynamic process of CO2 hydrate formation. The temporal-spatial evolution of CO2 hydrate formation is analyzed to reveal the generation and distribution of CO2 hydrate as a function of pressure and initial water saturation. The results reveal that CO2 hydrate mainly forms in macropores, where water-to-hydrate conversion rate exceeds 81%, while the conversion rate is below 27% in micropores. The spatial distribution of CO2 hydrate exhibits strong heterogeneity, and the hydrate formation preferentially occurs where the ratio of gas-water volume is 0.2-0.8. Increased injection pressure improved the heterogeneity, as evidenced by the increased heterogeneity index from 6.18 to 12.8. The increased injection pressure cannot enhance CO2-to-hydrate conversion at similar water saturation levels although improving the conversion rate of water-to-hydrate. Regardless of the initial water saturation, lower injection pressure has a higher CO2-to-hydrate conversion, approximately 95.2% (3MPa) and 86.5% (4MPa), respectively. This study advances the understanding of CO2 hydrate formation dynamics and demonstrates that lower injection pressure is more favorable for hydrate-based marine CO2 sequestration strategies.

Keywords: Hydrate-based marine CO2 sequestration; injection pressure; Initial water saturation; spatial-temporal distribution; LF-NMR

Fig.5 One-dimensional dynamic distribution of water volume in porous media during the hydrate formation. ((a) case 1: 3MPa; (b) case 2: 4MPa; (c) case 3: 5MPa; (d) case 4: 6MPa.)  

https://doi.org/10.1016/j.jgsce.2025.205734.

Phase equilibria of carbon dioxide + sulfur hexafluoride mixed gas hydrate as fundamental data toward improving the mechanical properties of marine sediments

二氧化碳+六氟化硫混合气体水合物的相平衡，作为改善海洋沉积物力学性能的基础数据

发表时间：2025年7月5日

发表期刊：《Fluid Phase Equilibria》

Tasuku Ishikawa a,b, Takeshi Sugahara a,b, Takayuki Hirai a,b, Norimasa Yoshimoto c

a Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, The University of Osaka, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan 

b Division of Energy and Photochemical Engineering, Research Center for Solar Energy Chemistry, Graduate School of Engineering Science, The University of Osaka, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan 

c Department of Civil and Environmental Engineering, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube,  Yamaguchi 755-8611, Japan

Abstract: Isothermal phase equilibria of carbon dioxide (CO2) + sulfur hexafluoride (SF6) mixed gas hydrate at temperatures of 281.85 K, 284.05 K, 288.05 K, 291.05 K, 291.74 K, and 292.20 K were measured so as to improve the mechanical properties of marine sediment by hydrate cementation. The addition of SF6 significantly reduces the equilibrium pressure of CO2-containing mixed gas hydrate at each temperature. At temperatures above the quadruple point Q2 (pure CO2 hydrate + aqueous + CO2-rich liquid + vapor phases) of 283.22 K, the four-phase (mixed gas hydrate + aqueous + guest-rich liquid + vapor phases) equilibrium point(s) exists(exist) on the isotherms of the CO2+SF6 mixed gas hydrate system. The four-phase equilibrium curve was connected from the quadruple point Q2 of pure CO2 hydrate to that of pure SF6 hydrate and had a maximum temperature point at 292.0 ± 0.2 K, which is higher than both the Q2temperatures of pure CO2 hydrate and pure SF6 hydrate. Therefore, the addition of SF6 to CO2 brings a significant effect to expand the thermodynamically stable region of CO2-containing mixed gas hydrate in order for simultaneous CO2storage and sediment improvement to be realized at marine sediment.

Keywords: Clathrate hydrate; Phase equilibria; CO2 storage; Ground improvement; Azeotropic-like behavior

Fig. 1. Isothermal pressure (p)-composition (y, vapor phase shown by red circles; z, hydrate phase shown by blue squares) phase equilibria in the CO2(1)+SF6(2) mixed gas hydrate system and isothermal vapor (y)-liquid (x) equilibria (VLE, green diamonds) in the CO2+SF6 binary system at (a) 281.85K, (b) 284.05K, (c) 288.05 K, (d) 291.05K, and (e) 291.74K. Solid curves represent the fftting curve of obtained isothermal phase equilibrium data as guides to the eye. The symbols x1, y1, and z1 represent the mole fractions of CO2 in guest-rich liquid, vapor, and hydrate phases on a water-free basis, respectively. At 291.05K and 291.74K, the compositional data in the hydrate phase were not measured because it was difffcult to measure them. 

https://doi.org/10.1016/j.fluid.2025.114525.