scholarly journals Dissociation and Self-Preservation of Gas Hydrates in Permafrost

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 431 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Boris Bukhanov ◽  
Dinara Davletshina ◽  
Sergey Grebenkin ◽  
Vladimir Istomin
Keyword(s):  
Phase Equilibrium ◽  
Gas Hydrates ◽  
Methane Hydrate ◽  
West Siberia ◽  
Gas Pressure ◽  
The Self ◽  
Frozen Soils ◽  
Long Time ◽  
Ice Content ◽  
Gas Bearing

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.

scholarly journals Formation and Accumulation of Pore Methane Hydrates in Permafrost: Experimental Modeling

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 467 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Dinara Davletshina
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Pore Space ◽  
Hydrate Formation ◽  
Methane Hydrates ◽  
Frozen Soils ◽  
Geological Models ◽  
Negative Temperatures ◽  
Thermobaric Conditions ◽  
Ice Content

Favorable thermobaric conditions of hydrate formation and the significant accumulation of methane, ice, and actual data on the presence of gas hydrates in permafrost suggest the possibility of their formation in the pore space of frozen soils at negative temperatures. In addition, today there are several geological models that involve the formation of gas hydrate accumulations in permafrost. To confirm the literature data, the formation of gas hydrates in permafrost saturated with methane has been studied experimentally using natural artificially frozen in the laboratory sand and silt samples, on a specially designed system at temperatures from 0 to −8 °C. The experimental results confirm that pore methane hydrates can form in gas-bearing frozen soils. The kinetics of gas hydrate accumulation in frozen soils was investigated in terms of dependence on the temperature, excess pressure, initial ice content, salinity, and type of soil. The process of hydrate formation in soil samples in time with falling temperature from +2 °C to −8 °C slows down. The fraction of pore ice converted to hydrate increased as the gas pressure exceeded the equilibrium. The optimal ice saturation values (45−65%) at which hydrate accumulation in the porous media is highest were found. The hydrate accumulation is slower in finer-grained sediments and saline soils. The several geological models are presented to substantiate the processes of natural hydrate formation in permafrost at negative temperatures.

scholarly journals Long-time discrete particle effects versus kinetic theory in the self-consistent single-wave model

2001 ◽  
Vol 64 (2) ◽  
Author(s):  
M-C. Firpo ◽  
F. Doveil ◽  
Y. Elskens ◽  
P. Bertrand ◽  
M. Poleni ◽  
...  
Keyword(s):  
Kinetic Theory ◽  
Wave Model ◽  
The Self ◽  
Single Wave ◽  
Discrete Particle ◽  
Self Consistent ◽  
Long Time

Insights into the self-preservation effect of methane hydrate at atmospheric pressure using high pressure DSC

2021 ◽  
Vol 86 ◽  
pp. 103738
Author(s):  
Xi-Yue Li ◽  
Dong-Liang Zhong ◽  
Peter Englezos ◽  
Yi-Yu Lu ◽  
Jin Yan ◽  
...  
Keyword(s):  
High Pressure ◽  
Atmospheric Pressure ◽  
Methane Hydrate ◽  
The Self ◽  
High Pressure Dsc

Quantification of methane hydrate formation in the Large-scale Reservoir Laboratory Simulator (LARS) by numerical simulations

2021 ◽  
Author(s):  
Zhen Li ◽  
Thomas Kempka ◽  
Erik Spangenberg ◽  
Judith Schicks
Keyword(s):  
Gas Hydrates ◽  
Methane Hydrate ◽  
Large Scale ◽  
Hydrate Formation ◽  
Simulation Environment ◽  
Transport Simulation ◽  
Chemistry Research ◽  
Research Activities ◽  
In Situ Conditions ◽  
Hydrate Bearing Sediments

&lt;p&gt;Natural gas hydrates are considered as one of the most promising alternatives to conventional fossil energy sources, and are thus subject to world-wide research activities for decades. Hydrate formation from methane dissolved in brine is a geogenic process, resulting in the accumulation of gas hydrates in sedimentary formations below the seabed or overlain by permafrost. The LArge scale Reservoir Simulator (LARS) has been developed (Schicks et al., 2011, 2013; Spangenberg et al., 2015) to investigate the formation and dissociation of gas hydrates under simulated in-situ conditions of hydrate deposits. Experimental measurements of the temperatures and bulk saturation of methane hydrates by electrical resistivity tomography have been used to determine the key parameters, describing and characterising methane hydrate formation dynamics in LARS. In the present study, a framework of equations of state to simulate equilibrium methane hydrate formation in LARS has been developed and coupled with the TRANsport Simulation Environment (Kempka, 2020) to study the dynamics of methane hydrate formation and quantify changes in the porous medium properties in LARS. We present our model implementation, its validation against TOUGH-HYDRATE (Gamwo &amp; Liu, 2010) and the findings of the model comparison against the hydrate formation experiments undertaken by Priegnitz et al. (2015). The latter demonstrates that our numerical model implementation is capable of reproducing the main processes of hydrate formation in LARS, and thus may be applied for experiment design as well as to investigate the process of hydrate formation at specific geological settings.&lt;/p&gt;&lt;p&gt;Key words: dissolved methane; hydrate formation; hydration; python; permeability.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Schicks, J. M., Spangenberg, E., Giese, R., Steinhauer, B., Klump, J., &amp; Luzi, M. (2011). New approaches for the production of hydrocarbons from hydrate bearing sediments. Energies, 4(1), 151-172, https://doi.org/10.3390/en4010151&lt;/p&gt;&lt;p&gt;Schicks, J. M., Spangenberg, E., Giese, R., Luzi-Helbing, M., Priegnitz, M., &amp; Beeskow-Strauch, B. (2013). A counter-current heat-exchange reactor for the thermal stimulation of hydrate-bearing sediments. Energies, 6(6), 3002-3016, https://doi.org/10.3390/en6063002&lt;/p&gt;&lt;p&gt;Spangenberg, E., Priegnitz, M., Heeschen, K., &amp; Schicks, J. M. (2015). Are laboratory-formed hydrate-bearing systems analogous to those in nature?. Journal of Chemical &amp; Engineering Data, 60(2), 258-268, https://doi.org/10.1021/je5005609&lt;/p&gt;&lt;p&gt;Kempka, T. (2020) Verification of a Python-based TRANsport Simulation Environment for density-driven fluid flow and coupled transport of heat and chemical species. Adv. Geosci., 54, 67&amp;#8211;77, https://doi.org/10.5194/adgeo-54-67-2020&lt;/p&gt;&lt;p&gt;Gamwo, I. K., &amp; Liu, Y. (2010). Mathematical modeling and numerical simulation of methane production in a hydrate reservoir. Industrial &amp; Engineering Chemistry Research, 49(11), 5231-5245, https://doi.org/10.1021/ie901452v&lt;/p&gt;&lt;p&gt;Priegnitz, M., Thaler, J., Spangenberg, E., Schicks, J. M., Schr&amp;#246;tter, J., &amp; Abendroth, S. (2015). Characterizing electrical properties and permeability changes of hydrate bearing sediments using ERT data. Geophysical Journal International, 202(3), 1599-1612, https://doi.org/10.1093/gji/ggv245&lt;/p&gt;

Peran Strategis Penyuluh Swadaya dalam Paradigma Baru Penyuluhan Pertanian Indonesia

2016 ◽  
Vol 32 (1) ◽  
pp. 43 ◽  
Author(s):  
NFN Syahyuti
Keyword(s):  
Agricultural Extension ◽  
Social Position ◽  
The Self ◽  
Extension System ◽  
Self Help ◽  
The Future ◽  
Long Time ◽  
The Government

<p><strong>English</strong><br />Involvement of farmers as actors to support extension activities have been underway for a long time with various approaches. In Indonesia, it started from the involvement of Kontak Tani (Advanced Farmers) in Supra Insus era, then farmer to farmer extension at P4S, as well as Penyuluh Swakarsa (Independent Extension Workers)” (in 2004), and the latest is Penyuluh Swadaya (Self-Help Agricultural Extension Workers) since 2008. The existence of self-help farmer extension workers are recognized since the enactment of Law No. 16/2006 on Extension System of Agricultural, Forestry and Fisheries. However, even though it runs nearly 10 years, the development of the role of self-help farmer extension workers is not optimal. This paper is a review of various posts including the recent research on self-help farmer extension workers and it aims to study the potential and problems of self-help farmer extension workers. It shows that the self-help farmer extension workers have a self-help capabilities and distinctive social position and they have to get right role. Appropriate support should be given to self-help farmer extension workers as the agricultural extension worker in the future and it must be distinguished between the government and private extension workers. </p><p> </p><p><strong>Indonesian</strong><br />Pelibatan petani sebagai pendukung dan pelaku langsung dalam kegiatan penyuluhan telah berlangsung cukup lama dengan berbagai pendekatan. Di Indonesia, hal ini dimulai dari pelibatan kontak tani pada era Bimas sampai Supra Insus, lalu pendekatan “penyuluhan dari petani ke petani” (farmer to farmer extension) di P4S, serta pengangkatan penyuluh swakarsa (tahun 2004), dan terakhir penyuluh swadaya (sejak tahun 2008). Keberadaan penyuluh swadaya diakui secara resmi semenjak diundangkannya UU No. 16 tahun 2006 tentang Sistem Penyuluhan Pertanian, Kehutanan dan Perikanan. Namun, meskipun sudah berjalan hampir 10 tahun, perkembangan peran penyuluh swadaya belum optimal. Tulisan ini merupakan review dari berbagai tulisan termasuk penelitian tentang penyuluh swadaya terakhir, untuk mempelajari potensi dan permasalahan penyuluh pertanian swadaya saat ini. Ditemukan bahwa penyuluh swadaya memiliki kapabilitas dan posisi sosial yang khas, sehingga batasan perannya mestilah diberikan secara tepat. Dukungan yang tepat harus diberikan kepada penyuluh swadaya sebagai sosok penyuluh pertanian yang strategis di masa mendatang, yang mesti dibedakan dengan penyuluh pemerintah dan penyuluh swasta.</p>

Effect of Fulvic Acid and Sodium Chloride on the Phase Equilibrium of Methane Hydrate in Mixed Sand–Clay Sediment

2019 ◽  
Vol 64 (2) ◽  
pp. 632-639 ◽  
Author(s):  
Tao Lv ◽  
Xiaosen Li ◽  
Zhaoyang Chen ◽  
Chungang Xu ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Phase Equilibrium ◽  
Sodium Chloride ◽  
Fulvic Acid ◽  
Methane Hydrate ◽  
Clay Sediment

Experimental Investigation of Methane Hydrate Formation in the Carboxmethylcellulose (CMC) Aqueous Solution

SPE Journal ◽  
2020 ◽  
Vol 25 (03) ◽  
pp. 1042-1056 ◽  
Author(s):  
Weiqi Fu ◽  
Zhiyuan Wang ◽  
Litao Chen ◽  
Baojiang Sun
Keyword(s):  
Aqueous Solution ◽  
Mass Transfer ◽  
Gas Hydrates ◽  
Methane Hydrate ◽  
Formation Rate ◽  
Hydrate Formation ◽  
Semiempirical Model ◽  
Stirred Reactor ◽  
Proposed Model ◽  
Wellbore Pressure

Summary In the development of deepwater crude oil, gas, and gas hydrates, hydrate formation during drilling operations becomes a crucial problem for flow assurance and wellbore pressure management. To study the characteristics of methane hydrate formation in the drilling fluid, the experiments of the methane hydrate formation in water with carboxmethylcellulose (CMC) additive are performed in a horizontal flow loop under flow velocity from 1.32 to 1.60 m/s and CMC concentration from 0.2 to 0.5 wt%. The flow pattern is observed as bubbly flow in experiments. The experiments indicate that the increase of CMC concentration impedes the hydrate formation while the increase of liquid velocity enhances formation rates. In the stirred reactor, the hydrate formation rate generally decreases as the subcooling condition decreases. However, in this work, with the subcooling condition continuously decreasing, hydrate formation rate follows a “U” shaped trend—initially decreasing, then leveling out and finally increasing. It is because the hydrate formation rate in this work is influenced by multiple factors, such as hydrate shell formation, fracturing, sloughing, and bubble breaking up, which has more complicated mass transfer procedure than that in the stirred reactor. A semiempirical model that is based on the mass transfer mechanism is developed for current experimental conditions, and can be used to predict the formation rates of gas hydrates in the non-Newtonian fluid by replacing corresponding correlations. The rheological experiments are performed to obtain the rheological model of the CMC aqueous solution for the proposed model. The overall hydrate formation coefficient in the proposed model is correlated with experimental data. The hydrate formation model is verified and the predicted quantity of gas hydrates has a discrepancy less than 10%.

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