The Principles of Complex Geocryological Geophysical Analysis for Studying Permafrost and Gas Hydrates on the Arctic Shelf of Russia

Destabilization of intrapermafrost gas hydrate is one possible reason for methane emission on the Arctic shelf. The formation of these intrapermafrost gas hydrates could occur almost simultaneously with the permafrost sediments due to the occurrence of a hydrate stability zone after sea regression and the subsequent deep cooling and freezing of sediments. The top of the gas hydrate stability zone could exist not only at depths of 200–250 m, but also higher due to local pressure increase in gas-saturated horizons during freezing. Formed at a shallow depth, intrapermafrost gas hydrates could later be preserved and transform into a metastable (relict) state. Under the conditions of submarine permafrost degradation, exactly relict hydrates located above the modern gas hydrate stability zone will, first of all, be involved in the decomposition process caused by negative temperature rising, permafrost thawing, and sediment salinity increasing. That’s why special experiments were conducted on the interaction of frozen sandy sediments containing relict methane hydrates with salt solutions of different concentrations at negative temperatures to assess the conditions of intrapermafrost gas hydrates dissociation. Experiments showed that the migration of salts into frozen hydrate-containing sediments activates the decomposition of pore gas hydrates and increase the methane emission. These results allowed for an understanding of the mechanism of massive methane release from bottom sediments of the East Siberian Arctic shelf.

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Optimal method of Arctic hydrocarbons production-and-supply system implementation

E3S Web of Conferences ◽

10.1051/e3sconf/202126601008 ◽

2021 ◽

Vol 266 ◽

pp. 01008

Author(s):

D.S. Bratskikh ◽

A.M. Schipachev ◽

V.A. Bukov

Keyword(s):

Natural Gas ◽

Gas Hydrates ◽

Barents Sea ◽

Arctic Shelf ◽

Hydraulic Calculation ◽

The Arctic ◽

Optimal Method ◽

Subsequent Formation ◽

Advantages And Disadvantages ◽

The Barents Sea

One of the most important issues in the development of the Arctic shelf is the rationality of transportation. Selection of the optimal method is an integral part of the project, in the framework of which this article is written. Earlier all possible methods and their advantages and disadvantages were evaluated. Within the framework of this article, t optimal method for the development of reserves on the Arctic shelf will be proposed, taking into account the possibilities of development and the effectiveness of subsequent transportation to the importing countries. The risks of gas hydrates were considered. The prospects of development of the Northern Sea Route between Russia and Asian countries are assessed; the cost of transportation of liquefied natural gas and compressed natural gas from the Barents Sea to Central Europe is compared. The hydraulic calculation of the selected section of the gas pipeline network is conducted. The economic calculation of the project as a whole is accomplished. The optimal location of the route in relation to the reserves in the Barents Sea has been chosen. Pressure losses in the selected zone were no more than 12.24 MPa with pipeline pressure from 8 to 16 MPa. In this case, condensation and subsequent formation of gas hydrates are not possible. Using only three sections of the network, the profit of the project will be 223 billion rubles per year. In accordance with this the best way of hydrocarbons realization in the Arctic is a combined method of transportation with modern methods of extraction and pipelaying laying.

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Role of Warming in Destabilization of Intrapermafrost Gas Hydrates in the Arctic Shelf: Experimental Modeling

Geosciences ◽

10.3390/geosciences9100407 ◽

2019 ◽

Vol 9 (10) ◽

pp. 407 ◽

Cited By ~ 5

Author(s):

Chuvilin ◽

Davletshina ◽

Ekimova ◽

Bukhanov ◽

Shakhova ◽

...

Keyword(s):

Gas Hydrates ◽

Methane Emission ◽

Gas Hydrate ◽

Arctic Shelf ◽

The Arctic ◽

Effect Of Temperature ◽

Permafrost Degradation ◽

Local Pressure ◽

Hydrate Dissociation ◽

Hydrate Stability

Destabilization of intrapermafrost gas hydrates is one of the possible mechanisms responsible for methane emission in the Arctic shelf. Intrapermafrost gas hydrates may be coeval to permafrost: they originated during regression and subsequent cooling and freezing of sediments, which created favorable conditions for hydrate stability. Local pressure increase in freezing gas-saturated sediments maintained gas hydrate stability from depths of 200–250 meters or shallower. The gas hydrates that formed within shallow permafrost have survived till present in the metastable (relict) state. The metastable gas hydrates located above the present stability zone may dissociate in the case of permafrost degradation as it becomes warmer and more saline. The effect of temperature increase on frozen sand and silt containing metastable pore methane hydrate is studied experimentally to reconstruct the conditions for intrapermafrost gas hydrate dissociation. The experiments show that the dissociation process in hydrate-bearing frozen sediments exposed to warming begins and ends before the onset of pore ice melting. The critical temperature sufficient for gas hydrate dissociation varies from −3.0 to −0.3 °C and depends on lithology (particle size) and salinity of the host frozen sediments. Taking into account an almost gradientless temperature distribution during degradation of subsea permafrost, even minor temperature increases can be expected to trigger large-scale dissociation of intrapermafrost hydrates. The ensuing active methane emission from the Arctic shelf sediments poses risks of geohazard and negative environmental impacts.

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Seismogenic-Triggering Mechanism of Gas Emission Activizations on the Arctic Shelf and Associated Phases of Abrupt Warming

Geosciences ◽

10.3390/geosciences10110428 ◽

2020 ◽

Vol 10 (11) ◽

pp. 428

Author(s):

Leopold Lobkovsky

Keyword(s):

Subduction Zone ◽

Climate Warming ◽

Gas Hydrates ◽

Time Lag ◽

Arctic Shelf ◽

The Arctic ◽

Aleutian Island ◽

Trigger Mechanism ◽

Methane Release ◽

Great Earthquakes

A seismogenic trigger mechanism is proposed to explain the abrupt climate warming phases in the Arctic as a result of strong mechanical disturbances in the marginal region of the Arctic lithosphere. Those disturbances might have been caused by great earthquakes in the Aleutian subduction zone, and slowly propagated across the Arctic shelf and adjacent regions, triggering the methane release from permafrost and metastable gas hydrates, followed by greenhouse gas emissions into the atmosphere. The proposed mechanism is based on the identified correlation between the series of the great earthquakes in the Aleutian island arc, which occurred in the early and middle of the 20th century, and the two phases of sharp climate warming, which began in 1920 and 1980. There is a 20-year time lag between these events, which is explained by the time of arrival of deformation waves in the lithosphere (propagating with a velocity of about 100 km per year) at the Arctic shelf and adjacent land from the Aleutian subduction zone, the region of their generation. The trigger mechanism causing the methane release from permafrost and metastable gas hydrates is related to the destruction of micro-sized ice films covering gas hydrate particles, the elements highly important for hydrate self-preservation, as well as destruction of gas-saturated micropores in permafrost rocks due to the slight additional stresses associated with deformation waves, and thus emergence of conditions favorable for gas filtration and its subsequent emission.

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