Hydrate nucleation in quiescent and dynamic conditions

Dai, Sheng; Lee, Joo Yong; Santamarina, J. Carlos

doi:10.1016/j.fluid.2014.07.006

Cited by 46 publications

(30 citation statements)

References 36 publications

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“…The decrease in the induction time of gas hydrate formation with the increase in the agitation intensity, which has been observed in a number of studies, can reasonably be attributed to the decrease in each of the identified components of t ind .…”

Section: Effect Of An Increase In Mixing Intensity On the Induction Timesupporting

confidence: 53%

“…Mechanical agitation is indeed a practical and economic way to decrease the induction time of gas hydrate formation. Nonetheless, the results of studies showing that an increase in agitation intensity leads to a decrease in induction time do not allow general conclusions to be drawn and used to develop mixing strategies that exploit this effect and that can be applied to systems or scales other than the ones used in the studies. First, more often than not, the experimental setups used in these studies consisted of small vessels agitated by a magnetic stirrer bar or, more rarely, by an impeller.…”

Section: Introductionmentioning

confidence: 99%

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Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation

et al. 2016

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A method that allows the effect of the fluid shear rate on the induction time of gas hydrate formation to be characterized was developed and applied to CO2‐THF hydrate formation. The investigation of the effect of the application of a constant shear rate (50 to 300 s−1) to the liquid phase from which the hydrates are formed revealed that the mean induction time decreases significantly as the applied shear rate increases. This could primarily be attributed to a decrease in the time required for stable gas hydrate nuclei to be generated and to grow to a macroscopically detectable size. The induction time could also be significantly reduced by the application of a high shear rate (900 s−1) to the liquid phase for a relatively short, defined period of time.

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Section: Effect Of An Increase In Mixing Intensity On the Induction Timesupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation

et al. 2016

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“…Temperature-time signatures all exhibit a common sequence of characteristic features: induction time, supercooling, or overpressuring prior to phase transformation, exothermic/endothermic transients during phase transformation (Figure 3: test 4. See Dai et al, 2014). P-T trajectories follow phase boundaries when phase transitions are involved, including water-ice, liquid-gas CO 2 , and the hydrate phase boundary (Figure 3: all cases).…”

Section: Results and Observationsmentioning

confidence: 99%

Laboratory Strategies for Hydrate Formation in Fine‐Grained Sediments

Lei

Santamarina

2018

JGR Solid Earth

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Fine‐grained sediments limit hydrate nucleation, shift the phase boundary, and hinder gas supply. Laboratory experiments in this study explore different strategies to overcome these challenges, including the use of a more soluble guest molecule rather than methane, grain‐scale gas‐storage within porous diatoms, ice‐to‐hydrate transformation to grow lenses at predefined locations, forced gas injection into water saturated sediments, and long‐term guest molecule transport. Tomographic images and thermal and pressure data provide rich information on hydrate formation and morphology. Results show that hydrate formation is inherently displacive in fine‐grained sediments; lenses are thicker and closer to each other in compressible, high specific surface area sediments subjected to low effective stress. Temperature and pressure trajectories follow a shifted phase boundary that is consistent with capillary effects. Exo‐pore growth results in freshly formed hydrate with a striped and porous structure; this open structure becomes an effective pathway for gas transport to the growing hydrate front. Ice‐to‐hydrate transformation goes through a liquid stage at premelt temperatures; then, capillarity and cryogenic suction compete, and some water becomes imbibed into the sediment faster than hydrate reformation. The geometry of hydrate lenses and the internal hydrate structure continue evolving long after the exothermal response to hydrate formation has completely decayed. Multiple time‐dependent processes occur during hydrate formation, including gas, water and heat transport, sediment compressibility, reaction rate, and the stochastic nucleation process. Hydrate formation strategies conceived for this study highlight the inherent difficulties in emulating hydrate formation in fine‐grained sediments within the relatively short time scale available for laboratory experiments.

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“…However, as revealed by X‐ray CT scanning, all specimens with higher hydrate volume fractions tend to have a relatively uniform hydrate distribution, while the specimens where hydrate accumulates preferentially at the core periphery and grows inwardly in a dendritic pattern have relatively lower hydrate volume fractions (refer to Figure ). The following underlying mechanisms govern these phenomena: Hydrate nucleation is inherently spontaneous and appears to be random in induction time, affected by the thermal history, physical properties, impurities, and mechanical agitation of the solution (Dai et al, ; Mullin, ). Thus, the location and the induction time (or subcooling temperature T sc ) of hydrate nucleation initiation are not predictable.…”

Section: Analyses and Discussionmentioning

confidence: 99%

Tetrahydrofuran Hydrate in Clayey Sediments—Laboratory Formation, Morphology, and Wave Characterization

et al. 2019

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Fine-grained sediments host more than 90% of gas hydrates on Earth. However, the fundamental properties of hydrate-bearing silty and clayey sediments are much less understood than those of hydrate-bearing sands, mainly due to the experimental challenges in synthesizing gas hydrate in fine-grained sediments in the laboratory as the way they form in nature. This study forms tetrahydrofuran (THF) hydrate in kaolinite, visualizes the hydrate distribution and morphology using X-ray computed tomography, and uses P and S waves to characterize the formed hydrate-bearing clayey sediments. The results show that THF hydrate formed in clay is innately segregated and heterogeneous, no longer as a pore constituent as in sandy sediments. Hydrate nucleation, growth, and distribution in clays are dominated by the thermal condition and constrained by water activity and mass transport, which can result in low stoichiometric-solution-to-hydrate conversion ratios of approximately 0.4-0.7. Thus, the estimation of hydrate volume in clays based on the mass of stoichiometric solution can be erroneous. The heterogeneity in hydrate-bearing clays imposes challenges in wave velocity based characterization. The bulk elastic properties of hydrate-bearing clays can be well predicted using the self-consistent model. Specimens with higher hydrate volume fraction VF h show higher wave attenuations Q −1 , highlighting the dominant role of THF hydrate in the wave attenuation of hydrate-bearing clays. The results suggest that Q p −1 = 0.08 + 0.4VF h = 2Q s −1 , which underlines the potential of using wave attenuation based methods to quantify the hydrate volume fraction in clayey sediments. Key Points:• Tetrahydrofuran hydrate formed in kaolinite clay is visualized using X-ray computed tomography and characterized using P and S waves • Hydrate nucleation and growth in clays are dominated by thermal conditions and constrained by water activity and mass transport • Specimens with higher hydrate saturation show higher wave attenuations, highlighting the dominant role of hydrate in the wave attenuation Supporting Information:• Supporting Information S1• Data Set S1• Data Set S2• Data Set S3• Data Set S4

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Hydrate nucleation in quiescent and dynamic conditions

Cited by 46 publications

References 36 publications

Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation

Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation

Laboratory Strategies for Hydrate Formation in Fine‐Grained Sediments

Tetrahydrofuran Hydrate in Clayey Sediments—Laboratory Formation, Morphology, and Wave Characterization

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Hydrate nucleation in quiescent and dynamic conditions

Cited by 46 publications

References 36 publications

Effect of the fluid shear rate on the induction time of CO2‐THF hydrate formation

Effect of the fluid shear rate on the induction time of CO2‐THF hydrate formation

Laboratory Strategies for Hydrate Formation in Fine‐Grained Sediments

Tetrahydrofuran Hydrate in Clayey Sediments—Laboratory Formation, Morphology, and Wave Characterization

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Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation

Effect of the fluid shear rate on the induction time of CO₂‐THF hydrate formation