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5 pages, 187 KiB

Open AccessEditorial

Permafrost and Gas Hydrate Response to Ground Warming

by Evgeny Chuvilin and Natalia Sokolova

Geosciences 2023, 13(9), 281; https://doi.org/10.3390/geosciences13090281 - 18 Sep 2023

Viewed by 1299

Abstract

This Special Issue of Geosciences is a collection of fifteen original research and overview papers on the response of permafrost and gas hydrates to ground warming caused by natural climate trends and industrial loads [...] Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

Research

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15 pages, 5436 KiB

Open AccessArticle

First Calibrated Methane Bubble Wintertime Observations in the Siberian Arctic Seas: Selected Results from the Fast Ice

by Denis Chernykh, Natalia Shakhova, Vladimir Yusupov, Elena Gershelis, Boris Morgunov and Igor Semiletov

Geosciences 2023, 13(8), 228; https://doi.org/10.3390/geosciences13080228 - 28 Jul 2023

Cited by 1 | Viewed by 1442

Abstract

This paper presents the results of an acoustic survey carried out from the fast ice in the shallow waters of the East Siberian Arctic Shelf (ESAS) using a single beam echosounder. The aim of this paper is to demonstrate an improved approach to [...] Read more.

This paper presents the results of an acoustic survey carried out from the fast ice in the shallow waters of the East Siberian Arctic Shelf (ESAS) using a single beam echosounder. The aim of this paper is to demonstrate an improved approach to study seafloor seepages in the Arctic coastal zone with an echosounder calibrated on site. During wintertime field observations of natural rising gas bubbles, we recorded three periods of their increased activity with a total of 63 short-term ejections of bubbles from the seabed. This study presents quantitative estimates of the methane (CH₄) flux obtained in wintertime at two levels of the water column: (1) at the bottom/water interface and (2) at the water/sea ice interface. In winter, the flux of CH₄ transported by rising bubbles to the bottom water in the shallow part of the ESAS was estimated at ~19 g·m⁻² per day, while the flux reaching the water/sea ice interface was calculated as ~15 g·m⁻² per day taking into account the diffusion of CH₄ in the surrounding water and the enrichment of rising bubbles with nitrogen and oxygen. We suggest that this bubble-transported CH₄ flux reaching the water /sea ice interface can be emitted into the atmosphere through numerous ice trenches, leads, and polynyas. This CH₄ ebullition value detected at the water/sea ice interface is in the mid high range of CH₄ ebullition value estimated for the entire ESAS, and two orders higher than the upper range of CH₄ ebullition from the northern thermocarst lakes, which are considered as a significant source to the atmospheric methane budget. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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23 pages, 4288 KiB

Open AccessArticle

Late Mesozoic and Cenozoic Geodynamics of the Arctic Region: Implications for Abiogenic Generation of Hydrocarbons

by Nickolay Sorokhtin, Leopold Lobkovsky, Igor Semiletov, Eduard Shipilov, Sergey Nikiforov, Nikolay Kozlov, Natalia Shakhova, Roman Ananiev and Dmitry Alekseev

Geosciences 2023, 13(3), 68; https://doi.org/10.3390/geosciences13030068 - 28 Feb 2023

Cited by 2 | Viewed by 2087

Abstract

Late Mesozoic and Cenozoic geodynamics of the Arctic region is discussed in the context of possible mechanisms which provide multistage cyclic transformations and transport of carbon through crust and mantle. Geodynamic processes control the abiogenic generation of hydrocarbons and the patterns of their [...] Read more.

Late Mesozoic and Cenozoic geodynamics of the Arctic region is discussed in the context of possible mechanisms which provide multistage cyclic transformations and transport of carbon through crust and mantle. Geodynamic processes control the abiogenic generation of hydrocarbons and the patterns of their localization. Possible mechanisms of abiotic hydrocarbon generation are explained in the context of carbon transport from subduction zones to rifts and serpentinization of ultramafic rocks in the rifts in the case of the Laptev Sea and Gakkel Ridge areas. The carbon of shallow crust origin migrates with encapsulated fragments of marine sediments which are consumed in the Pacific subduction zone where they become destroyed and transformed by different chemical and physical processes. The resulting C-species are involved in mantle convection flows and reach the continental rifts of the Laptev Sea and the Gakkel mid-ocean ridge. Thus, the hydrocarbons formed in the crust and in the mantle acquire signatures of abiotic origin. According to the authors, the scale of manifestation of abiogenic methanogenesis in the lower parts of the lithosphere and in the upper mantle is not so wide. Numerous small (mm and fractions of the mm) particles of exogenous matter and dispersed carbon pulled into the mantle can only form a stable crustal geochemical plume that propagates in the plane of movement of convective flows. Indirectly, the scale of manifestation of this process can be judged by the volumes of degassing of hydrocarbon and carbon dioxide gases, as well as hydrogen and its compounds in the rift systems of the earth’s crust, which are extremely insignificant. However, in the cold seas of the Eastern Arctic, massive emissions of bubble methane of mixed genesis were found. As shown in the literature, the range of variability of stable isotopes of carbon and ¹⁴C of methane in certain areas of discharge associated with rifting demonstrates values (anomalously heavy ¹³C, and young ¹⁴C) that can be considered as examples of presumably abiogenic origin. Our work is mostly theoretical and suggests further discussion and improvement of the mechanism of formation of abiogenic hydrocarbons and the processes of their transformation. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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10 pages, 3668 KiB

Open AccessArticle

The Model of Cohesionless Sediment Blowout with an Increase in the Methane Flow Rate

by Polina M. Shpak, Sergey B. Turuntaev, Mariia A. Trimonova, Aliya A. Tairova, Georgiy V. Belyakov and Nikita A. Iudochkin

Geosciences 2022, 12(11), 423; https://doi.org/10.3390/geosciences12110423 - 17 Nov 2022

Cited by 2 | Viewed by 1537

Abstract

Dissociation of methane hydrates in the Arctic permafrost may lead to explosive gas emission. Methane blowout may be triggered by increasing gas flow rate at a certain depth. The mechanism of rock failure and blowout under the effect of pressurized gas was studied [...] Read more.

Dissociation of methane hydrates in the Arctic permafrost may lead to explosive gas emission. Methane blowout may be triggered by increasing gas flow rate at a certain depth. The mechanism of rock failure and blowout under the effect of pressurized gas was studied numerically and in laboratory experiments. The problem was formulated for the unsteady flow of compressed gas depending on the flow rate at a given depth, and pore gas pressure variations were calculated as a function of depth and time. The model parameters were chosen with reference to field data. According to the model, the input of gas to friable material at an increasing rate may lead to gas blowout and density loss propagating downward as the gas pressure exceeds the overburden pressure at some depth. The laboratory system was of the type of a Hele-Shaw cell, with small glass balls as friable material confined between two glass panels. The results of physical modeling and calculations show good agreement. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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17 pages, 6928 KiB

Open AccessArticle

Formation of Metastability of Pore Gas Hydrates in Frozen Sediments: Experimental Evidence

by Evgeny Chuvilin, Dinara Davletshina, Boris Bukhanov, Aliya Mukhametdinova and Vladimir Istomin

Geosciences 2022, 12(11), 419; https://doi.org/10.3390/geosciences12110419 - 14 Nov 2022

Cited by 3 | Viewed by 2171

Abstract

The Arctic permafrost and zones of hydrate stability may evolve to the conditions that allow gas hydrates to remain metastable for a long time due to self-preservation within 150 m depths. The behavior of relict (metastable) gas hydrates in frozen sediments is controlled [...] Read more.

The Arctic permafrost and zones of hydrate stability may evolve to the conditions that allow gas hydrates to remain metastable for a long time due to self-preservation within 150 m depths. The behavior of relict (metastable) gas hydrates in frozen sediments is controlled externally by pressure and temperature and internally by the properties of hydrate particles and sediments. The sensitivity of the dissociation and self-preservation of pore gas hydrates to different factors is investigated in laboratory experiments. The observations focus on time-dependent changes in methane hydrate saturation in frozen sand samples upon the pressure dropping below phase equilibrium in the gas–hydrate–ice system. The preservation of pore gas hydrates in these conditions mainly depends on the initial hydrate and ice saturation, clay contents and mineralogy, salinity, and texture of sediments, which affect the size, shape, and structure distortion of hydrate inclusions. The self-preservation mechanism works well at high initial contents of pore ice and hydrate, low salinity, relatively low percentages of clay particles, temperatures below −4 °C, and below-equilibrium pressures. Nuclear magnetic resonance (NMR) measurements reveal considerable amounts of unfrozen pore water in frozen sediments that may hold for several days after the pressure drop, which controls the dissociation and self-preservation processes. Metastable gas hydrates in frozen sand may occupy up to 25% of the pore space, and their dissociation upon permafrost thawing and pressure drops may release up to 16 m³ of methane into the atmosphere per 1 m³ of hydrate-bearing permafrost. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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15 pages, 12919 KiB

Open AccessArticle

Imaging Arctic Permafrost: Modeling for Choice of Geophysical Methods

by Igor Buddo, Natalya Misyurkeeva, Ivan Shelokhov, Evgeny Chuvilin, Alexey Chernikh and Alexander Smirnov

Geosciences 2022, 12(10), 389; https://doi.org/10.3390/geosciences12100389 - 21 Oct 2022

Cited by 7 | Viewed by 2654

Abstract

Knowledge of permafrost structure, with accumulations of free natural gas and gas hydrates, is indispensable for coping with spontaneous gas emission and other problems related to exploration and production drilling in Arctic petroleum provinces. The existing geophysical methods have different potentialities for imaging [...] Read more.

Knowledge of permafrost structure, with accumulations of free natural gas and gas hydrates, is indispensable for coping with spontaneous gas emission and other problems related to exploration and production drilling in Arctic petroleum provinces. The existing geophysical methods have different potentialities for imaging the permafrost base and geometry, vertical fluid conduits (permeable zones), taliks, gas pockets, and gas hydrate accumulations in the continental Arctic areas. The synthesis of data on cryological and geological conditions was the basis for a geophysical–geological model of northern West Siberia to a depth of 400 m, which includes modern permafrost, lenses of relict permafrost with hypothetical gas hydrates, and a permeable zone that may be a path for the migration of gas–water fluids. The model was used to model synthetic seismic, electrical resistivity tomography (ERT), and transient electromagnetic (TEM) data, thus testing the advantages and drawbacks of the three methods. Electrical resistivity tomography has insufficient penetration to resolve all features and can run only in the summer season. Seismic surveys have limitations in mapping fluid conduits, though they can image a horizontally layered structure in any season. Shallow transient electromagnetic (sTEM) soundings can image any type of features included into the geological model and work all year round. Thus, the best strategy is to use TEM surveys as the main method, combined with seismic and ERT data. Each specific method is chosen proceeding from economic viability and feasibility in the specific physiographic conditions of mountain and river systems. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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17 pages, 7193 KiB

Open AccessArticle

Trigger Mechanisms of Gas Hydrate Decomposition, Methane Emissions, and Glacier Breakups in Polar Regions as a Result of Tectonic Wave Deformation

by Leopold I. Lobkovsky, Alexey A. Baranov, Mukamay M. Ramazanov, Irina S. Vladimirova, Yurii V. Gabsatarov, Igor P. Semiletov and Dmitry A. Alekseev

Geosciences 2022, 12(10), 372; https://doi.org/10.3390/geosciences12100372 - 8 Oct 2022

Cited by 17 | Viewed by 4869

Abstract

Trigger mechanisms are proposed for gas hydrate decomposition, methane emissions, and glacier collapse in polar regions. These mechanisms are due to tectonic deformation waves in the lithosphere–asthenosphere system, caused by large earthquakes in subduction zones, located near the polar regions: the Aleutian arc, [...] Read more.

Trigger mechanisms are proposed for gas hydrate decomposition, methane emissions, and glacier collapse in polar regions. These mechanisms are due to tectonic deformation waves in the lithosphere–asthenosphere system, caused by large earthquakes in subduction zones, located near the polar regions: the Aleutian arc, closest to the Arctic, and the Antarctica–Chilean and Tonga–Kermadec–Macquarie subduction zones. Disturbances of the lithosphere are transmitted over long distances (of the order of 2000–3000 km and more) at a speed of about 100 km/year. Additional stresses associated with them come to the Arctic and Antarctica several decades after the occurrence of seismic events. On the Arctic shelf, additional stresses destroy the microstructure of metastable gas hydrates located in frozen rocks at shallow depths, releasing the methane trapped in them and leading to filtration and emissions. In West Antarctica, these wave stresses lead to decreases in the adhesions of the covered glaciers with underlying bedrock, sharp accelerations of their sliding into the sea, and fault occurrences, reducing pressure on the underlying rocks containing gas hydrates, which leads to their decomposition and methane emissions. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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18 pages, 2856 KiB

Open AccessArticle

Mathematical Model of the Decomposition of Unstable Gas Hydrate Accumulations in the Cryolithozone

by Leopold I. Lobkovsky, Mukamay M. Ramazanov, Igor P. Semiletov and Dmitry A. Alekseev

Geosciences 2022, 12(9), 345; https://doi.org/10.3390/geosciences12090345 - 16 Sep 2022

Cited by 3 | Viewed by 1739

Abstract

We present a generalization of the mathematical model of gas discharge from frozen rocks containing gas-saturated ice and gas hydrates in a metastable state (due to the self-preservation effect) caused by the drop in external stress associated with various geodynamic factors. These factors [...] Read more.

We present a generalization of the mathematical model of gas discharge from frozen rocks containing gas-saturated ice and gas hydrates in a metastable state (due to the self-preservation effect) caused by the drop in external stress associated with various geodynamic factors. These factors can be attributed, for example, to a decrease in hydrostatic pressure on a gas-bearing formation due to glacier melting, causing an isostatic rise, or to the formation of linear depressions in the bottom topography on the shelf due to iceberg ploughing. A change in external pressure can also be associated with seismic and tectonic deformation waves propagating in the lithosphere as a result of ongoing strong earthquakes. Starting from the existing hydrate destruction model, operating at the scale of individual granules, we consider a low-permeable hydrate and ice-saturated horizontal reservoir. Generalization is associated with the introduction of a finite threshold for the external pressure drop, which causes the destruction of the gas hydrate and gas-saturated microcavities of supramolecular size. This makes it possible to take into account the effect of anomalously high pressures occurring in the released gas as a result of partial hydrate dissociation. Numerical and approximate analytical solutions to the problem were found in the self-similar formulation. A parametric study of the solution was carried out, and regularities of the hydrate decomposition process were revealed. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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14 pages, 2502 KiB

Open AccessArticle

Gas Permeability Behavior in Frozen Sand Controlled by Formation and Dissociation of Pore Gas Hydrates

by Evgeny Chuvilin, Maksim Zhmaev and Sergey Grebenkin

Geosciences 2022, 12(9), 321; https://doi.org/10.3390/geosciences12090321 - 28 Aug 2022

Cited by 3 | Viewed by 2250

Abstract

Formation and dissociation of pore gas hydrates in permafrost can change its properties, including fluid flow capacity. Permeability is one of the most significant parameters in the study of hydrate-containing rocks, especially in the case of gas burial or extraction. Gas permeability variations [...] Read more.

Formation and dissociation of pore gas hydrates in permafrost can change its properties, including fluid flow capacity. Permeability is one of the most significant parameters in the study of hydrate-containing rocks, especially in the case of gas burial or extraction. Gas permeability variations in frozen sand partially saturated with CO₂ or CH₄ hydrates are studied experimentally at a constant negative temperature of −5 °C, as well as during freezing–thawing cycles. The gas permeability behavior is controlled by the formation and dissociation of pore gas hydrates in frozen sand samples. The samples with an initial ice saturation of 40 to 60% become at least half as permeable, as 40% of pore ice converts to hydrate. The dissociation process of accumulated hydrates was modeled by both depressurizing methane or CO₂ to atmospheric pressure and by stepwise injection of gaseous nitrogen up to 3 MPa into a frozen sample. In sand samples, with a decrease in gas pressure and without subsequent injection of nitrogen, a decrease in pore hydrate dissociation due to self-preservation was noted, which is reflected by a deceleration of gas permeability. Nitrogen injection did not lead to a decrease in the rate of dissociation in the frozen hydrate-containing sample, respectively, as there was no decrease in the rate of gas permeability. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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11 pages, 45316 KiB

Open AccessArticle

Echo Sounding for Remote Estimation of Seabed Temperatures on the Arctic Shelf

by Vladimir Yusupov, Aleksandr Salomatin, Natalia Shakhova, Denis Chernykh, Anna Domaniuk and Igor Semiletov

Geosciences 2022, 12(9), 315; https://doi.org/10.3390/geosciences12090315 - 25 Aug 2022

Cited by 4 | Viewed by 1654

Abstract

The East Siberian Arctic Shelf (ESAS) is a key area of CH₄ venting in the Arctic Ocean. The ESAS region stores more than 80% of the world’s predicted subsea permafrost and associated permafrost-related gas hydrates. Gas emissions from subsea permafrost are controlled [...] Read more.

The East Siberian Arctic Shelf (ESAS) is a key area of CH₄ venting in the Arctic Ocean. The ESAS region stores more than 80% of the world’s predicted subsea permafrost and associated permafrost-related gas hydrates. Gas emissions from subsea permafrost are controlled by its current thermal state, which, in turn, depends on environmental factors. The aim of the manuscript is to show that the thermal state of subsea permafrost and phase transitions of its pore moisture can be estimated remotely by echo soundings, which can resolve the structure of shallow bottom sediments. It has been found that the duration of the seabed acoustic response (echo duration, Δ) at frequencies of 50 and 200 kHz correlates with sediment temperatures and generally increases with cooling below 0.5 °C. This correlation, explained by assuming a layered structure of the bottom sediments, establishes the basis for high-frequency acoustic thermometry. The technique is an advantageous tool for many applications: fast contouring of low-temperature zones, remote measurements of seabed surface temperature, and estimation of the thickness of frozen sediments near the bottom. The latter estimates have implications for the distribution of subsea permafrost and the stability of gas hydrates on the Arctic shelf. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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13 pages, 3171 KiB

Open AccessArticle

Reline Jacket: Efficient Reduction of Frost-Heave Uplift of Piles in Warming Permafrost

by Dmitriy Alyavdin, Vladimir Belyakov, Artemiy Levin, Andrey Alekseev, Erika Grechishcheva, Olga Kozlova and Roman Makhota

Geosciences 2022, 12(9), 313; https://doi.org/10.3390/geosciences12090313 - 23 Aug 2022

Cited by 3 | Viewed by 2530

Abstract

Air temperature in the Northern Hemisphere has been progressively warming in the recent decades, and the ground temperatures have increased correspondingly. The air temperature increasing due to the climate change induces degradation of permafrost and frost heaving activation. The frost heaving forces cause [...] Read more.

Air temperature in the Northern Hemisphere has been progressively warming in the recent decades, and the ground temperatures have increased correspondingly. The air temperature increasing due to the climate change induces degradation of permafrost and frost heaving activation. The frost heaving forces cause unevenly distributed damaging displacement of foundations and thus poses problems to the development of Arctic regions. Frost-heave uplift forces can be reduced by protecting piles with an OSPTReline (or Reline) polymer heat-shrinkable jacket. The interaction of heaving soil with a pile covered with the Reline jacket is modeled in laboratory to estimate the uplift force and the related shear strength of frozen soil along the soil-pile adfreeze surface at temperatures from −6 to −1 °C. The data are obtained for silty sand and silty clay soils and mortar (1:5 cement-sand mixture). The experiments show that frost-heave uplift forces on Reline-protected piles are 52% to 85% lower than on uncovered steel piles (steel grade 09G2S—analog to European steel grade S355JR), depending on soil type and temperature. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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19 pages, 10364 KiB

Open AccessArticle

Migration of Salt Ions in Frozen Hydrate-Saturated Sediments: Temperature and Chemistry Constraints

by Evgeny Chuvilin, Valentina Ekimova, Dinara Davletshina, Boris Bukhanov, Ekaterina Krivokhat and Vladimir Shilenkov

Geosciences 2022, 12(7), 276; https://doi.org/10.3390/geosciences12070276 - 9 Jul 2022

Cited by 3 | Viewed by 2252

Abstract

Migration of dissolved salts from natural (cryopeg brines, seawater, etc.), or artificial sources can destabilize intrapermafrost gas hydrates. Salt transport patterns vary as a function of gas pressure, temperature, salinity, etc. The sensitivity of the salt migration and hydrate dissociation processes to ambient [...] Read more.

Migration of dissolved salts from natural (cryopeg brines, seawater, etc.), or artificial sources can destabilize intrapermafrost gas hydrates. Salt transport patterns vary as a function of gas pressure, temperature, salinity, etc. The sensitivity of the salt migration and hydrate dissociation processes to ambient temperature and to the concentration and chemistry of saline solutions is investigated experimentally on frozen sand samples at a constant negative temperature (−6 °C). The experiments show that the ambient temperature and the solution chemistry control the critical salt concentration required for complete gas hydrate dissociation. Salt ions migrate faster from more saline solutions at higher temperatures, and the pore moisture can reach the critical salinity in a shorter time. The flux density and contents of different salt ions transported to the samples increase in the series Na₂SO₄–KCl–CaCl₂–NaCl–MgCl₂. A model is suggested to account for phase transitions of pore moisture in frozen hydrate-saturated sediments exposed to contact with concentrated saline solutions at pressures above and below the thermodynamic equilibrium, in stable and metastable conditions of gas hydrates, respectively. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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15 pages, 3928 KiB

Open AccessArticle

Temperature Variation during Salt Migration in Frozen Hydrate-Bearing Sediments: Experimental Modeling

by Evgeny Chuvilin, Valentina Ekimova, Dinara Davletshina, Boris Bukhanov, Ekaterina Krivokhat and Vladimir Shilenkov

Geosciences 2022, 12(7), 261; https://doi.org/10.3390/geosciences12070261 - 27 Jun 2022

Cited by 6 | Viewed by 2457

Abstract

Salt migration may be another reason why pore-gas hydrates dissociate in permafrost, besides pressure and temperature changes. Temperature variations in frozen hydrate-saturated sediments interacting with a NaCl solution have been studied experimentally at a constant temperature, ~−6 °C typical for permafrost. The experiments [...] Read more.

Salt migration may be another reason why pore-gas hydrates dissociate in permafrost, besides pressure and temperature changes. Temperature variations in frozen hydrate-saturated sediments interacting with a NaCl solution have been studied experimentally at a constant temperature, ~−6 °C typical for permafrost. The experiments with frozen sandy samples containing metastable methane hydrate show that the migration of Na+ ions in the NaCl solution and their accumulation in the sediments can induce heat-consuming hydrate dissociation and ice melting. The hydrate-saturated frozen soils cool down at higher rates than their hydrate-free counterparts and require more time to recover their initial temperature. The temperature effects in hydrate-saturated frozen sediments exposed to contact with NaCl solutions depend strongly on salt concentration. The experimental results are used to model phase changes in the pore space associated with salt-ions transport and provide insights into the reasons for temperature changes. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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13 pages, 2686 KiB

Open AccessArticle

Changes in Unfrozen Water Contents in Warming Permafrost Soils

by Evgeny Chuvilin, Natalia Sokolova and Boris Bukhanov

Geosciences 2022, 12(6), 253; https://doi.org/10.3390/geosciences12060253 - 17 Jun 2022

Cited by 4 | Viewed by 2459

Abstract

Climate warming in the Arctic, accompanied by changes in permafrost soil properties (mechanical, thermal, filtration, geophysical), is due to increasing unfrozen pore water content. The liquid component in frozen soils is an issue of key importance for permafrost engineering that has been extensively [...] Read more.

Climate warming in the Arctic, accompanied by changes in permafrost soil properties (mechanical, thermal, filtration, geophysical), is due to increasing unfrozen pore water content. The liquid component in frozen soils is an issue of key importance for permafrost engineering that has been extensively studied since the beginning of the 20th century. We suggest a synthesis and new classification of various experimental and calculation methods for the determination of unfrozen water content. Special focus is placed on the method of applying measurements to the water potential, which reveals the impact of permafrost warming on unfrozen water content. This method was applied to natural soil samples collected from shallow permafrost from northern West Siberia affected by climate change, and confirms the revealed trends. The obtained results confirm that unfrozen water content is sensitive not only temperature but also particle size distribution, salinity, and the organic matter content of permafrost soils. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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18 pages, 5251 KiB

Open AccessArticle

Simulating Thermal Interaction of Gas Production Wells with Relict Gas Hydrate-Bearing Permafrost

by Evgeny Chuvilin, Gennadiy Tipenko, Boris Bukhanov, Vladimir Istomin and Dimitri Pissarenko

Geosciences 2022, 12(3), 115; https://doi.org/10.3390/geosciences12030115 - 2 Mar 2022

Cited by 9 | Viewed by 4501

Abstract

The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas [...] Read more.

The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas hydrate dissociation) upon permafrost thawing. The solution is derived from the energy conservation within the modeling domain by solving a quasilinear thermal conductivity equation. The calculations are determined for a well completion with three casing strings and the heat insulation of a gas lifting pipe down to a depth of 55 m. The thermal parameters of permafrost are selected according to laboratory and field measurements from the Bovanenkovo gas-condensate field in the Yamal Peninsula. The modeling results refer to the Bovanenkovo field area and include the size of the thawing zone around wells, with regard to free methane release as a result of gas hydrate dissociation in degrading permafrost. The radius of thawing around a gas well with noninsulated lifting pipes operating for 30 years may reach 10 m or more, while in the case of insulated lifting pipes, no thawing is expected. As predicted by the modeling for the Bovanenkovo field, methane emission upon the dissociation of gas hydrates caused by permafrost thawing around producing gas wells may reach 400,000–500,000 m³ over 30 years. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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15 pages, 3103 KiB

Open AccessArticle

Formation of Gas-Emission Craters in Northern West Siberia: Shallow Controls

by Evgeny Mikhailovich Chuvilin, Natalia Sergeevna Sokolova, Boris Aleksandrovich Bukhanov, Dinara Anvarovna Davletshina and Mikhail Yurievich Spasennykh

Geosciences 2021, 11(9), 393; https://doi.org/10.3390/geosciences11090393 - 17 Sep 2021

Cited by 12 | Viewed by 7792

Abstract

Gas-emission craters discovered in northern West Siberia may arise under a specific combination of shallow and deep-seated permafrost conditions. A formation model for such craters is suggested based on cryological and geological data from the Yamal Peninsula, where shallow permafrost encloses thick ground [...] Read more.

Gas-emission craters discovered in northern West Siberia may arise under a specific combination of shallow and deep-seated permafrost conditions. A formation model for such craters is suggested based on cryological and geological data from the Yamal Peninsula, where shallow permafrost encloses thick ground ice and lenses of intra- and subpermafrost saline cold water (cryopegs). Additionally, the permafrost in the area is highly saturated with gas and stores large accumulations of hydrocarbons that release gas-water fluids rising to the surface through faulted and fractured crusts. Gas emission craters in the Arctic can form in the presence of gas-filled cavities in ground ice caused by climate warming, rich sources of gas that can migrate and accumulate under pressure in the cavities, intrapermafrost gas-water fluids that circulate more rapidly in degrading permafrost, or weak permafrost caps over gas pools. Full article

(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)

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