Laboratory formation of noncementing hydrates in sandy sediments

Choi, Jeong‐Hoon; Dai, Sheng; Cha, Jong-Ho; Seol, Yongkoo

doi:10.1002/2014gc005287

Cited by 58 publications

(49 citation statements)

References 39 publications

(66 reference statements)

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“…Compressional and shear wave velocity measurement of THF hydrate‐bearing sediments under water‐saturated condition confirms that hydrate nucleation starts at pore space, and hydrates grow following pore‐filling model as long as hydrate saturation S h is lower than ~40% [ Waite et al ., ; Yun et al ., ]. This noncementing behavior is also found in methane hydrate‐bearing sediments under water‐saturated condition [ Choi et al ., ; Yokoyama et al ., ].…”

Section: Results and Analysesmentioning

confidence: 99%

The effect of hydrate saturation on water retention curves in hydrate‐bearing sediments

Mahabadi

Zheng

Jang

2016

Geophysical Research Letters

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The experimental measurement of water retention curve in hydrate‐bearing sediments is critically important to understand the behavior of hydrate dissociation and gas production. In this study, tetrahydrofuran (THF) is selected as hydrate former. The pore habit of THF hydrates is investigated by visual observation in a transparent micromodel. It is confirmed that THF hydrates are not wetting phase on the quartz surface of the micromodel and occupy either an entire pore or part of pore space resulting in change in pore size distribution. And the measurement of water retention curves in THF hydrate‐bearing sediments with hydrate saturation ranging from Sh = 0 to Sh = 0.7 is conducted for excess water condition. The experimental results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Based on the experimental results, fitting parameters for van Genuchten equation are suggested for different hydrate saturation conditions.

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Section: Results and Analysesmentioning

confidence: 99%

The effect of hydrate saturation on water retention curves in hydrate‐bearing sediments

Mahabadi

Zheng

Jang

2016

Geophysical Research Letters

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“…Choi et al, 2014;Lee et al, 2013;Priest et al, 2009), estimate the smallstrain bulk-, shear-and compressional-moduli as well as the Poisson's ratio (Helgerud et al, 2009;Lee et al, 2010a), and link seismic and well log measurements to in situ hydrate saturations (e.g. Fohrmann and Pecher, 2012;Hunter et al, 2011;Shankar and Riedel, 2014;Shelander et al, 2012).…”

Section: Small-strain Properties: Wave Velocities and Modulimentioning

confidence: 99%

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Santamarina

Dai

Terzariol

et al. 2015

Marine and Petroleum Geology

207

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a b s t r a c tNatural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy-and clayey-silts. Hydrate saturations S h range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on neverdepressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where S h exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy-and clayey-silts, where S h < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressureetemperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The firstever direct shear measurements on never-depressurized pressure-core specimens show hydratebearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.Published by Elsevier Ltd.

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“…GHs in sediments are usually characterized either to be pore‐filling and having only a minor effect on stress‐strain behavior or to be grain‐coating or load‐bearing with larger mechanical effects (Hyodo, Li, et al, ; Priest et al, ). Which type is formed preferentially depends on S h and the pore fluid composition with a tendency of pore‐filling GHs to occur under gas‐limited conditions, and grain‐coating GHs being formed in water‐limited sediments (Choi et al, ; Ebinuma et al, ; Priest et al, ). Experimental studies have evaluated effects of varying S h (e.g., Masui et al, ; Santamarina & Ruppel, ), temperatures (Jia et al, ; Song et al, ), pore pressures ( u , Jiang, Zhu, et al, ), and effective stresses ( σ 3 ′, Lee, Francisca, et al, ; Miyazaki, Tenma, et al, ) to identify relevant parameters and initial conditions in the geotechnical analysis of GHBS.…”

Section: Introductionmentioning

confidence: 99%

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

Deusner

Gupta

Xie

et al. 2019

Geochem Geophys Geosyst

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The presence of gas hydrates (GHs) increases the stiffness and strength of marine sediments. In elasto‐plastic constitutive models, it is common to consider GH saturation (Sh) as key internal variable for defining the contribution of GHs to composite soil mechanical behavior. However, the stress‐strain behavior of GH‐bearing sediments (GHBS) also depends on the microscale distribution of GH and on GH‐sediment fabrics. A thorough analysis of GHBS is difficult, because there is no unique relation between Sh and GH morphology. To improve the understanding of stress‐strain behavior of GHBS in terms of established soil models, this study summarizes results from triaxial compression tests with different Sh, pore fluids, effective confining stresses, and strain histories. Our data indicate that the mechanical behavior of GHBS strongly depends on Sh and GH morphology, and also on the strain‐induced alteration of GH‐sediment fabrics. Hardening‐softening characteristics of GHBS are strain rate‐dependent, which suggests that GH‐sediment fabrics dynamically rearrange during plastic yielding events. We hypothesize that rearrangement of GH‐sediment fabrics, through viscous deformation or transient dissociation and reformation of GHs, results in kinematic hardening, suppressed softening, and secondary strength recovery, which could potentially mitigate or counteract large‐strain failure events. For constitutive modeling approaches, we suggest that strain rate‐dependent micromechanical effects from alterations of the GH‐sediment fabrics can be lumped into a nonconstant residual friction parameter. We propose simple empirical evolution functions for the mechanical properties and calibrate the model parameters against the experimental data.

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Laboratory formation of noncementing hydrates in sandy sediments

Cited by 58 publications

References 39 publications

The effect of hydrate saturation on water retention curves in hydrate‐bearing sediments

The effect of hydrate saturation on water retention curves in hydrate‐bearing sediments

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

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