scholarly journals Forecast of Distribution and Thickness of Gas Hydrate Stability Zone at the Bottom of the Caspian Sea

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6019
Author(s):  
Vasily Bogoyavlensky ◽  
Alisa Yanchevskaya ◽  
Aleksei Kishankov
Keyword(s):  
Gas Hydrates ◽  
Caspian Sea ◽  
Geothermal Gradient ◽  
Methane Hydrates ◽  
Gas Composition ◽  
Stability Zone ◽  
The South ◽  
The Caspian Sea ◽  
Hydrocarbon Production ◽  
Hydrate Stability

The Caspian Sea is a region of active hydrocarbon production, where apart from conventional accumulations, gas hydrates (GH) are known to exist. GH are a potential future source of energy, however, currently they pose danger for development of conventional fields. The goal of this research was to determine the area of GH distribution and thickness of their stability zone in the Caspian Sea using numerical modeling and to define how certain parameters affect the calculated thickness. As a result of the research, cartographic schemes were created for the South and Middle Caspian, where GH were predicted. For the South Caspian, conditions for methane hydrates formation exist at depths of more than 419–454 m, and for the Middle Caspian, more than 416–453 m. The maximal thicknesses of methane hydrates stability zones for the South Caspian can reach 900–956 m, and for the Middle Caspian, 226–676 m. Variations of parameters of seafloor depth, geothermal gradient and gas composition can significantly change the resulting thickness of GH stability zone.

scholarly journals Distribution of the gas hydrate stability zone in the Ross Sea, Antarctica

2017 ◽  
Vol 45 (1) ◽  
pp. 78 ◽  
Author(s):  
Michela Giustiniani ◽  
Umberta Tinivella ◽  
Chiara Sauli ◽  
Bruno Della Vedova
Keyword(s):  
Gas Hydrates ◽  
Ross Sea ◽  
Geothermal Gradient ◽  
Simple Approach ◽  
Stability Zone ◽  
Bottom Temperature ◽  
Bathymetric Data ◽  
Sea Bottom ◽  
Sea Area ◽  
Hydrate Stability

The theoretical gas hydrates stability zone (GHSZ) in the Ross Sea area was evaluated by mean of a steady state simple approach by using bathymetric data, sea bottom temperature, a variable geothermal gradient and assuming that the natural gas is methane. The results from our study suggest that bathymetry and distribution of the GHSZ are correlated; in fact, the GHSZ reaches a maximum (ca. 400 m) in the basins, where the water temperature is the lowest, and decreases in the banks with thickness ranging between 7 and

scholarly journals Role of Salt Migration in Destabilization of Intra Permafrost Hydrates in the Arctic Shelf: Experimental Modeling

Geosciences ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 188 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Valentina Ekimova ◽  
Boris Bukhanov ◽  
Sergey Grebenkin ◽  
Natalia Shakhova ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Methane Emission ◽  
Gas Hydrate ◽  
Negative Temperature ◽  
Arctic Shelf ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Stability Zone ◽  
Local Pressure ◽  
Hydrate Stability

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.

scholarly journals Numerical modelling of the Caspian Sea tides

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 209-219
Author(s):  
Igor P. Medvedev ◽  
Evgueni A. Kulikov ◽  
Isaac V. Fine
Keyword(s):  
Caspian Sea ◽  
Ocean Model ◽  
Tidal Range ◽  
The South ◽  
Tidal Dynamics ◽  
The Caspian Sea ◽  
Sea Levels ◽  
The North ◽  
Anticlockwise Rotation ◽  
Diurnal Tides

Abstract. The Caspian Sea is the largest enclosed basin on Earth and a unique subject for the analysis of tidal dynamics. Tides in the basin are produced directly by the tide-generating forces. Using the Princeton Ocean Model (POM), we examine details of the spatial and temporal features of the tidal dynamics in the Caspian Sea. We present tidal charts of the amplitudes and phase lags of the major tidal constituents, together with maps of the form factor, tidal range, and tidal current speed. Semi-diurnal tides in the Caspian Sea are determined by a Taylor amphidromic system with anticlockwise rotation. The largest M2 amplitude is 6 cm and is located in Türkmen Aylagy (called Turkmen Bay hereafter). For the diurnal constituents, the Absheron Peninsula separates two individual amphidromes with anticlockwise rotation in the north and in the south. The maximum K1 amplitudes (up to 0.7–0.8 cm) are located in (1) the south-eastern part of the basin, (2) Türkmenbaşy Gulf, (3) Mangyshlak Bay; and (4) Kizlyar Bay. As a result, the semi-diurnal tides prevail over diurnal tides in the Caspian Sea. The maximum tidal range, of up to 21 cm, has been found in Turkmen Bay. The strongest tidal currents have been located in the straits to the north and south of Ogurja Ada, where speeds reach 22 and 19 cm s−1, respectively. Numerical simulations of the tides using different mean sea levels (within a range of 5 m) indicate that spatial features of the Caspian Sea tides are strongly sensitive to changes in mean sea level.

The Cadusii in Archaeology? Remarks on the Achaemenid Period (Iron Age IV) in Gilan and Talesh

2013 ◽  
Vol 17 (2) ◽  
pp. 115-151
Author(s):  
Christian Konrad Piller
Keyword(s):  
Material Culture ◽  
Iron Age ◽  
Caspian Sea ◽  
Point Of View ◽  
Armed Conflicts ◽  
The South ◽  
The Caspian Sea ◽  
Material Basis ◽  
South West ◽  
New Material

According to some classical authors, the region south-west of the Caspian Sea was inhabited by the large tribe of the Cadusians (Greek Καδουσιοι, Latin Cadusii). During the Achaemenid Period, several armed conflicts between the Imperial Persian forces and the warlike Cadusians occurred. Of particular importance is the disastrous defeat of Artaxerxes II in 380 B.C. From the archaeological point of view, little has been known about the material culture of the Achaemenid Period (Iron Age IV) in Talesh and Gilan. Until recently, only a few burial contexts from the South of Gilan could be dated to the period between the 6th and 4th centuries B.C. However, during the last two decades, Iranian archaeologists excavated numerous Bronze and Iron Age graveyards in the Talesh Region. A number of burial contexts at sites, such as Maryan, Mianroud or Vaske can securely be dated to the Achaemenid Period. With this new material basis, it was possible to subdivide the Iron Age IV into different subsequent phases. Furthermore, it is likely that the material culture described in this article could be at least partially attributed to the Cadusians.

Seismic attribute enhancement of weak and discontinuous gas hydrate bottom-simulating reflectors in the Pegasus Basin, New Zealand

2019 ◽  
Vol 7 (3) ◽  
pp. SG11-SG22 ◽  
Author(s):  
Heather Bedle
Keyword(s):  
New Zealand ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Rock Physics ◽  
Stability Zone ◽  
Seismic Attribute ◽  
Rock Physics Modeling ◽  
Physics Modeling ◽  
Hydrate Stability

Gas hydrates in the oceanic subsurface are often difficult to image with reflection seismic data, particularly when the strata run parallel to the seafloor and in regions that lack the presence of a bottom-simulating reflector (BSR). To address and understand these imaging complications, rock-physics modeling and seismic attribute analysis are performed on modern 2D lines in the Pegasus Basin in New Zealand, where the BSR is not continuously imaged. Based on rock-physics and seismic analyses, several seismic attribute methods identify weak BSR reflections, with the far-angle stack data being particularly effective. Rock modeling results demonstrate that far-offset seismic data are critical in improving the imaging and interpretation of the base of the gas hydrate stability zone. The rock-physics modeling results are applied to the Pegasus 2009 2D data set that reveals a very weak seismic reflection at the base of the hydrates in the far-angle stack. This often-discontinuous reflection is significantly weaker in amplitude than typical BSRs associated with hydrates. These weak far-angle stack BSRs often do not appear clearly in full stack data, the most commonly interpreted seismic data type. Additional amplitude variation with angle (AVA) attribute analyses provide insight into identifying the presence of gas hydrates in regions lacking a strong BSR. Although dozens of seismic attributes were investigated for their ability to reveal weak reflections at the base of the gas hydrate stability zone, those that enhance class 2 AVA anomalies were most effective, particularly the seismic fluid factor attribute.

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