• Economic and Environmental Geology
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• v.46 no.1
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• pp.71-84
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• 2013

Most gas hydrates (GH) occur in ocean sediments. Global GH reserves are estimated to be $10^{13}{\sim}20{\times}10^{15}m^3$, which is nearly 1,000 times the amount of current world energy consumption. Methane hydrate (MH) has the potential to be developed into future natural gas resources to replace traditional oil and gas resources, and thus MH production technologies such as depressurization, inhibitor injection, thermal stimulation, and $CO_2-CH_4$ substitution need to be further developed. MH production, which is expected to be in test production until 2014 in Korea, is focused on the development of GH production technologies for use in the commercial production of methane gas. This study compares MH production technology and its ability to meet the twin goals of being both effective and environmentally friendly while taking into consideration the complex phenomena of GH decomposition.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.146.2-146.2
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• 2011

Molecular behaviors and crystal structures of the binary hydrates of $CH_4$ and ethanol were identified by means of 13C solid-state NMR and powder XRD methods at various concentrations of ethanol. In addition, NMR peak areas were used to calculate cage occupancies for both guest species. Obtained results showed that more $CH_4$ molecules are captured into hydrate phase per unit mass of ethanol molecules because $CH_4$ molecule can occupy sII large cages more, and pure $CH_4$ hydrate can form more as well at lower ethanol concentrations. Even though tuning phenomenon was already reported for some aqueous hydrate promoters such as THF, aqueous ethanol solutions are found to play the same tuning role in the binary clathrate hydrates in this study.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.58-61
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• 2006

n-Pentane and n-hexane, previously regarded as non-hydrate formers, are found to form structure H hydrate in mixtures with 2,2-dimethylbutane. Even though they are thought to be too large to fit into the largest cage of the structure H hydrate, powder XRD and NMR measurements show that they form gas hydrates in mixtures with other sH hydrate former. These findings are of fundamental interest and also will impact the composition and location of natural gas hydrates and their potential as global energy resource and climate change materials.

• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.94-101
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• 2006

[ $1m^3$ ] solid hydrate contains up to $200m^3$ of natural gas, depending on pressure and temperature. Such large volume of natural gas hydrate can be utilized to store and transport large quantity of natural gas in a stable condition. So, in the present investigation, experiments carried out for the formation of natural gas hydrate governed by pressure, temperature, and gas compositions, etc.. The results show that the equilibrium pressure of structure II natural gas hydrate) is approximately 65% lower and the solubility is approximately three times higher than structure I methane hydrate). Also, the subcooling conditions of the structure I and II must be above 9K and 11K in order to form hydrate rapidly regardless of gas components, but the pressure increase is more advantageous than the temperature decrease in order to increase the gas consumption. And utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.399-402
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• 2006

[ $1m^3$ ] solid hydrate contains up to $200m^3$ of natural gas, depending on pressure and temperature. Such large volume of natural gas hydrate can be utilized to store and transport large quantity of natural gas in a stable condition. So, in the present investigation, experiments carried out for the formation of natural gas hydrate governed by pressure, temperature, and gas compositions, etc.. The results show that the equilibrium pressure of structure II natural gas hydrate (is approximately 65% lower and the solubility is approximately three times higher than structure I methane hydrate). Also, the subcooling conditions of the structure I and II must be above 9K and 11K in order to form hydrate rapidly regardless of gas components, but the pressure increase is more advantageous than the temperature decrease in order to increase the gas consumption. And utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.151-151
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• 2011

Large amounts of natural gas, mainly methane, in the form of hydrates are stored on continental margins. When gas hydrates are dissociated by any environmental trigger, generation of excess pore pressure due to released free gas may cause sediment deformation and weakening. Hence, damage on offshore structures or submarine landslide can occur by gas hydrate dissociation. Therefore, geotechnical stability of gas hydrate bearing sediments is in need to be securely assessed. However, geotechnical characteristics of gas hydrates bearing sediments including small-strain elastic moduli have been poorly identified. Synthesizing gas hydrate in natural seabed sediment specimen, which is mainly composed of silty-to-clayey soils, has been hardly attempted due to their low permeability. Moreover, it has been known that hydrate loci in pore spaces and heterogeneity of hydrate growth in specimen scale play a critical role in determining physical properties of hydrate bearing sediments. In the presented study, we synthesized gas hydrate containing sediments in an instrumented oedometric cell. Geotechnical and geophysical properties of gas hydrate bearing sediments including compressibility, small-strain elastic moduli, elastic wave, and electrical resistivity are determined by wave-based techniques during loading and unloading processes. Significant changes in volume change, elastic wave, and electrical resistivity have been observed during formation and dissociation of gas hydrate. Experimental results and analyses reveal that geotechnical properties of gas hydrates bearing sediments are highly governed by hydrate saturation, effective stress, void ratio, and soil types as well as morphological feature of hydrate formation in sediments.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.890-893
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• 2012

Gas hydrates are solid crystal structures formed by enclathration of gaseous guest species into 3-dimensional lattice structure of hydrogen-bonded water molecules. These compounds can be potentially used as an energy storage/transportation medium because they can hold a large amount of gas in a small volume of the solid phase. In addition, huge amount of natural gas, buried in seabeds or permafrost region in the form of the solid hydrate, is regarded as a future energy source. In this study, synthesized natural gas, whose composition is 90.0 mol% of methane, 7.0 mol% of ethane, and 3.0 mol% of propane, was used to identify formation behaviors of natural gas hydrates for the purpose of applying the gas hydrate to a storage/transportation medium of natural gas. According to the experimental results obtained by means of the solid-state NMR and high-resolution powder XRD methods, it is found that formed natural gas hydrates have crystal structure of the structure-II hydrate, and that methane occupies both small and large cages, while the others only occupy large ones. In addition, both the NMR spectroscopy and the gas chromatograph showed that there exists preferential occupation among the natural gas components during the hydrate formation. Compositional changes after the hydrate formation revealed that the preferential occupation is in order of propane, ethane, and methane (propane is the most preferential guest species when forming natural gas hydrates).

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.712-715
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• 2009

본 연구에서는 고밀도, 고촉진 가스하이드레이트 생성 촉진제 (promoter)의 개발을 위하여 음이온성 멀티체인형 게면활성제를 제조하였다. 또한 각 계면활성제의 알킬그룹의 길이에 따라 같은 조건에서의 계면활성제의 촉진 효과를 비교하였다. $1^{\circ}C$에서 35bar,40bar로 압력을 달리하여 비교 실험하여 메탄 하이드레이트 생성속도를 측정하고, 각 조건에서의 계면활성제의 촉진 효과를 비교하였다. 알킬그룹의 길이가 짧을수록, 압력이 높을수록 촉진 속도가 빠르다. 또한 기존의 상용화된 SDS(Sodium dodecyl sulfate)보다 본 연구에서 제조한 C10의 음이온성 멀티체인형 계면활성제가 SDS 대비하여 소량으로도 충분한 효과를 나타냄을 확인하였다.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.241-246
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• 2000

Gas hydrates are solid solutions when water molecules are linked through hydrogen bondin create host lattice cavities that can enclose a large variety of guest gas molecules. The natural hydrate crystal may exist at low temperature above the normal freezing point of water and pressure greater than about 30 bars. A lot of quantities of natural gas hydrates exists in the ear many production schemes are being studied. In the present investigation, depressurization method considered to predict the production of gas and the simulation of the two phase flow - gas and - in porous media is being carried out. The simulation show about the fluid flow in porous have a variety of applications in industry. Results provide the appearance of gas and water prod the pressure profile, the saturation of gas/ water/ hydrates profiles and the location of the pl front.

• New & Renewable Energy
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• v.2 no.3
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• pp.37-41
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• 2006

In this study, an experimental apparatus has been designed and set up to analyze the dissociating phenomena of hydrate in porous rock. Experiments with the depressurization scheme have been carried out to investigate the dissociation characteristics of methane hydrates and the productivities of dissociated gas and water. From the experiments, it has been provided a determination of volume of gas produced and the progress of the dissociation front, as a function of time when hydrate is depressurized. Also, it has been investigated the flowing behavior of the dissociated gas and water in porous rock and the efficiency of the production