Effect of Ice and Hydrate Formation on Thermal Conductivity of Sediments

Chuvilin, Evgeny; Bukhanov, Boris; Cheverev, V.G.; Motenko, R. G.; Grechishcheva, E.

doi:10.5772/intechopen.75383

Cited by 6 publications

(7 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Salinity affects the preservation of hydrates as far as it controls phase change of pore moisture and amount of unfrozen water because the presence of liquid water slows down the formation of ice films over hydrate crystals and decreases their density. The contents of unfrozen water increase with salinity [60], which is unfavorable for the existence of pore hydrates, especially in the metastable state. As shown by our experiments, prolonged preservation of pore hydrates in frozen sand samples (fine sand 1 and fine sand 3) was possible at salinity within ~0.1%.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Dissociation and Self-Preservation of Gas Hydrates in Permafrost

et al. 2018

Self Cite

View full text Add to dashboard Cite

Gases releasing from shallow permafrost above 150 m may contain methane produced by the dissociation of pore metastable gas hydrates, which can exist in permafrost due to self-preservation. In this study, special experiments were conducted to study the self-preservation kinetics. For this, sandy samples from gas-bearing permafrost horizons in West Siberia were first saturated with methane hydrate and frozen and then exposed to gas pressure drop below the triple-phase equilibrium in the “gas–gas hydrate–ice” system. The experimental results showed that methane hydrate could survive for a long time in frozen soils at temperatures of −5 to −7 °C at below-equilibrium pressures, thus evidencing the self-preservation effect. The self-preservation of gas hydrates in permafrost depends on its temperature, salinity, ice content, and gas pressure. Prolonged preservation of metastable relict hydrates is possible in ice-rich sandy permafrost at −4 to −5 °C or colder, with a salinity of <0.1% at depths below 20–30 m.

show abstract

Section: Resultsmentioning

confidence: 99%

“…Additionally, thermal conductivity, mechanic strength, and gas permeability of the samples were measured in some runs at disequilibrium conditions [57][58][59][60][61].…”

Section: Methodsmentioning

confidence: 99%

Dissociation and Self-Preservation of Gas Hydrates in Permafrost

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…A change in the thermal regime of a permafrost-hydrate system after its submergence would lead to partial thawing of permafrost, causing destabilization of intra-permafrost hydrates; this would be manifested as patchy (mosaic, spotty) gas releases over the destabilized areas [5,14,15,21,68]. The fraction of intra-permafrost hydrates was suggested to not only survive the thawing cycle due to the self-preservation phenomenon, but also to become denser and more saturated owing to recrystallization caused by repeated freeze-thaw cycles [69]. On the other hand, salt propagating into the permafrost as brine increases the content of unfrozen water, which is unfavorable for metastable hydrates stability [69].…”

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

“…The fraction of intra-permafrost hydrates was suggested to not only survive the thawing cycle due to the self-preservation phenomenon, but also to become denser and more saturated owing to recrystallization caused by repeated freeze-thaw cycles [69]. On the other hand, salt propagating into the permafrost as brine increases the content of unfrozen water, which is unfavorable for metastable hydrates stability [69]. Specific features of Arctic hydrates include: (1) Occurring three times more frequently offshore than onshore [13]; (2) high spatial concentration and thick layers (up to 110 m); (3) extremely high pore saturation, up to 100% of pore space [13]; and (4) higher sensitivity to warming and lower sensitivity to pressure change [63,70].…”

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

2019

Self Cite

View full text Add to dashboard Cite

This paper summarizes current understanding of the processes that determine the dynamics of the subsea permafrost-hydrate system existing in the largest, shallowest shelf in the Arctic Ocean; the East Siberian Arctic Shelf (ESAS). We review key environmental factors and mechanisms that determine formation, current dynamics, and thermal state of subsea permafrost, mechanisms of its destabilization, and rates of its thawing; a full section of this paper is devoted to this topic. Another important question regards the possible existence of permafrost-related hydrates at shallow ground depth and in the shallow shelf environment. We review the history of and earlier insights about the topic followed by an extensive review of experimental work to establish the physics of shallow Arctic hydrates. We also provide a principal (simplified) scheme explaining the normal and altered dynamics of the permafrost-hydrate system as glacial-interglacial climate epochs alternate. We also review specific features of methane releases determined by the current state of the subsea-permafrost system and possible future dynamics. This review presents methane results obtained in the ESAS during two periods: 1994-2000 and 2003-2017. A final section is devoted to discussing future work that is required to achieve an improved understanding of the subject.Significant reserves of CH 4 are held in the Arctic seabed [10], but the release of CH 4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years [11]. In the regions where permafrost exists, hydrate-bearing sediment deposits can reach a thickness of 400 to 800 m [12,13]. Shallow hydrate deposits are predicted to occupy~57% (1.25 × 10 6 km 2 ) of the East Siberian Arctic Shelf (ESAS) seabed [14]. It has been suggested that destabilization of shelf Arctic hydrates could lead to large-scale enhancement of aqueous CH 4 , but this process was hypothesized to be negligible on a decadal-century time scale [15].Consequently, the continental shelf of the Arctic Ocean (AO) has not been considered as a possible source of CH 4 to the atmosphere until very recently [16][17][18].The key area of the AO for atmospheric venting of CH 4 is the East Siberian Arctic Shelf (ESAS). The ESAS covers greater than two million square kilometers (equal to the areas of Germany, France, Great Britain, Italy, and Japan combined). This vast yet shallow region has recently been shown to be a significant modern source of atmospheric CH 4 , contributing annually no less than terrestrial Arctic ecosystems [19,20]; but unlike terrestrial ecosystems, the ESAS emits CH 4 year-round due to its partial openness during the winter when terrestrial ecosystems are dormant [21]. Emissions are determined by and dependent on the current thermal state of the subsea permafrost and environmental factors controlling permafrost dynamics [21,22]. Releases could potentially increase by 3-5 orders of magnitude,...

show abstract

“…Unfortunately, today there is practically no experimental data of thermal properties of gas hydrates and hydrate-bearing sediments at non-equilibrium conditions (at temperature below 0 • C), except only few publications [23,24] (because most of the publications have covered the thermal properties of gas hydrates and hydrate-contain sediments at stable conditions which are important for methane production from gas hydrates reservoirs [25][26][27][28][29][30][31][32][33][34][35]). The obtained results at non-equilibrium conditions show that the thermal conductivity of frozen hydrate-bearing sediments may change by several times during the self-preservation effect and differs from the thermal conductivity of frozen hydrate-free and hydrate-bearing soils contain stable gas hydrates [36,37]. This study is a continuation of the early works and it is important for understanding the processes of hydrates dissociation in both natural and technical conditions since the processes of heat transfer often determine the rate of these processes.…”

Section: Introductionmentioning

confidence: 93%

Thermal Conductivity of Frozen Sediments Containing Self-Preserved Pore Gas Hydrates at Atmospheric Pressure: An Experimental Study

Chuvilin

Bukhanov

2019

Geosciences

Self Cite

View full text Add to dashboard Cite

The paper presents the results of an experimental thermal conductivity study of frozen artificial and natural gas hydrate-bearing sediments at atmospheric pressure (0.1 MPa). Samples of hydrate-saturated sediments are highly stable and suitable for the determination of their physical properties, including thermal conductivity, due to the self-preservation of pore methane hydrate at negative temperatures. It is suggested to measure the thermal conductivity of frozen sediments containing self-preserved pore hydrates by a KD-2 needle probe which causes very little thermal impact on the samples. As shown by the special measurements of reference materials with known thermal conductivities, the values measured with the KD-2 probe are up to 20% underestimated and require the respective correction. Frozen hydrate-bearing sediments differ markedly in thermal conductivity from reference frozen samples of the same composition but free from pore hydrate. The difference depends on the physical properties of the sediments and on changes in their texture and structure associated with the self-preservation effect. Namely, it increases proportionally to the volumetric hydrate content, hydrate saturation, and the percentage of water converted to hydrate. Thermal conductivity is anisotropic in core samples of naturally frozen sediments that enclose visible ice-hydrate lenses and varies with the direction of measurements with respect to the lenses. Thermal conductivity measurements with the suggested method provide a reliable tool for detection of stable and relict gas hydrates in permafrost.

show abstract

Effect of Ice and Hydrate Formation on Thermal Conductivity of Sediments

Cited by 6 publications

References 34 publications

Dissociation and Self-Preservation of Gas Hydrates in Permafrost

Dissociation and Self-Preservation of Gas Hydrates in Permafrost

Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

Thermal Conductivity of Frozen Sediments Containing Self-Preserved Pore Gas Hydrates at Atmospheric Pressure: An Experimental Study

Contact Info

Product

Resources

About