• Title, Summary, Keyword: gas hydrate

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Gas Hydrate Exploration by using PCS(Pressre Core Sampler): ODP Leg 204 (압력코어를 이용한 가스 하이드레이트 탐사: ODP Leg 204)

  • Lee Young-Joo
    • Economic and Environmental Geology
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    • v.38 no.2
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    • pp.165-176
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    • 2005
  • Natural gas in deep sediment may occur in three phases based on the physical and chemical conditions. If the concentration of gas in pore water is less than the solubility, gas is dissolved. If the concentration of gas is greater than its solubility (water is saturated or supersaturated with gas), gas occurs as a fee gas below the gas hydrate stability Lone (GHSZ) and is present as solid hydrate within the GHSZ. The knowledge of gas concentration in deep sediment appears critical to determine the phase of natural gases and to understand the formation and distribution of gas hydrate. However, reliable data on gas concentration are usually available only from the upper section of marine sediment by the headspace gas technique, which is widely used for sampling of gases from the sediments. The headspace gas technique represents only a fraction of gases present in situ because sediments release most of the gases during recovery and sampling. The PCS (Pressure Core Sampler) is a downhole tool developed to recover a nominal $1{\cal}m$ long, $4.32{\cal}cm$ diameter core containing $1,465cm^3$ of sediment, pore water and gas at in situ pressure up to 68.9 MPa. During Leg 204, the PCS was deployed at 6 Sites. In situ methane gas concentration and distribution of gas hydrate was measured by using PCS tool. Characteristics of methane concentration and distribution is different from site to site. Distribution of gas hydrate in the study area is closely related to characteristics of in situ gas concentration measured by PCS.

NUMERICAL ANALYSIS OF NON-EQUILIBRIUM HYDRATE PELLET DECOMPOSITION (하이드레이트 펠릿의 비평형 분해과정 수치해석)

  • Kang, Jung-Ho;Nam, Jin-Hyun;Kim, Charn-Jung;Song, Myung-Ho
    • 한국전산유체공학회:학술대회논문집
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    • pp.268-275
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    • 2008
  • The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

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NUMERICAL ANALYSIS OF NON-EQUILIBRIUM HYDRATE PELLET DECOMPOSITION (하이드레이트 펠릿의 비평형 분해과정 수치해석)

  • Kang, Jung-Ho;Nam, Jin-Hyun;Kim, Charn-Jung;Song, Myung-Ho
    • 한국전산유체공학회:학술대회논문집
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    • pp.268-275
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    • 2008
  • The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

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NUMERICAL ANALYSIS OF NON-EQUILIBRIUM HYDRATE PELLET DECOMPOSITION (하이드레이트 펠릿의 비평형 분해과정 수치해석)

  • Kang, Jung-Ho;Nam, Jin-Hyun;Kim, Charn-Jung;Song, Myung-Ho
    • Journal of computational fluids engineering
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    • v.13 no.4
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    • pp.50-57
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    • 2008
  • The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

Experimental Study on Injection Rate Effects during Gas Hydrate Production using Flue Gas Swapping Method (가스하이드레이트 배가스 치환 시 주입유속의 영향에 관한 실험적 연구)

  • Lee, Dong-Gun;Lee, Joo-Yong;Lee, Min-Hui;Lee, Jae-Hyung
    • 한국신재생에너지학회:학술대회논문집
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    • pp.196-199
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    • 2008
  • In this study, gas hydrate production has been followed using swapping method to investigate the effect of injection rate of flue gas and soaking period in unconsolidated artificial sand sample. The results shows that recovery factor of methane gas decreases with increasing the injection rate of flue gas. This indicates that the velocity of flue gas in porous media may act as kinds of inhibitor for production of hydrate. Also recovery factor increases with increasing the soaking time.

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A new approach for modeling of multicomponent gas hydrate formation

  • Mohebbi, Vahid;Behbahani, Reza Mosayyebi;Naderifar, Abbas
    • Korean Journal of Chemical Engineering
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    • v.34 no.3
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    • pp.706-716
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    • 2017
  • Several models have been proposed to investigate the kinetics of gas hydrate formation. The main differences between the proposed models are the definition of the driving force, thermodynamics approach and the number of resistances to study the gas consumption by the hydrate phase. This paper concentrates on gas hydrate formation from multicomponent mixture, which has not been much studied before. In the present research, chemical potential has been considered as the driving force and, consequently, a new resistance coefficient was introduced. A complete discussion and reasonable assumptions has been provided to support this modelling.

Seismic properties of Gas Hydrate using Modeling Technique (모델링 기술을 이용한 심해 Gas Hydrate의 탄성파 특성 연구)

  • Shin, Sung-Ryul;Yeo, Eun-Min;Kim, Chan-Su;Kim, Young-Jun;Park, Keun-Pil;Lee, Ho-Young
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.156-157
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    • 2005
  • Gas hydrate is ice-like crystalline lattice, formed at appropriate temperature and pressure, in which gas molecules are trapped. It is worldwide popular interesting subject as a potential energy. In korea, a seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. In this paper, we had conducted numerical and physical modeling experiments for seismic properties on gas hydrate with field data which had been acquired over the East sea in 1998. We used a finite difference seismic method with staggered grid for 2-D elastic wave equation to generate synthetic seismograms from multi-channel surface seismic survey, OBC(Ocean Bottom Cable) and VSP(Vertical Seismic Profiling). We developed the seismic physical modeling system which is simulated in the deep sea conditions and acquired the physical model data to the various source-receiver geometry. We carried out seismic complex analysis with the obtained data. In numerical and physical modeling data, we observed the phase reversal phenomenon of reflection wave at interface between the gas hydrate and free gas. In seismic physical modeling, seismic properties of the modeling material agree with the seismic velocity estimated from the travel time of reflection events. We could easily find out AVO(Amplitude Versus Offset) in the reflection strength profile through seismic complex analysis.

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The Analysis of Dissociation Properties According to Gas Hydrate Saturation and Depressurization Rate (가스하이드레이트 포화율 및 감압률에 따른 해리특성 분석)

  • An, Seung-Hee;Chon, Bo-Hyun
    • Journal of the Korean Institute of Gas
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    • v.19 no.3
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    • pp.54-59
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    • 2015
  • The gas hydrate of 10 trillion tons are buried under continental slope in the world(permafrost : 2%, marine continental slope: 98%), but technology for the the commercial gas recovery has not developed yet. There are normally four representative recovery methods: depressurization method, thermal stimulation method, inhibition injection method, and displacement method. This study focuses on change of dissociation time and gas production according to gas hydrate saturation rate and depressurization rate. It was found that the correlation between depressrization rate and dissociation time was like as $Y=0.0004X^2-0.499X+176.86$. It was also found that the bigger depressurization rate is, the better production is(methane gas is produced over 46.2% at depressurization rate 50% compared with 40%). However, on the contrary to this, it is presumed that gas production is decreased at 60% due to gas hydrate reformation.

Pre-Combustion Capture of Carbon Dioxide Using Principles of Gas Hydrate Formation (가스 하이드레이트 형성 원리를 이용한 연소전 탈탄소화 연구)

  • Lee, Hyun-Ju;Lee, Ju-Dong;Kim, Yang-Do
    • Korean Journal of Materials Research
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    • v.18 no.12
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    • pp.650-654
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    • 2008
  • The emission of carbon dioxide from the burning of fossil fuels has been identified as a major contributor to green house emissions and subsequent global warming and climate changes. For these reasons, it is necessary to separate and recover $CO_2$ gas. A new process based on gas hydrate crystallization is proposed for the $CO_2$ separation/recovery of the gas mixture. In this study, gas hydrate from $CO_2/H_2$ gas mixtures was formed in a semi-batch stirred vessel at a constant pressure and temperature. This mixture is of interest to $CO_2$ separation and recovery in Integrated Coal Gasification (IGCC) plants. The impact of tetrahydrofuran (THF) on hydrate formation from the $CO_2/H_2$ was observed. The addition of THF not only reduced the equilibrium formation conditions significantly but also helped ease the formation of hydrates. This study illustrates the concept and provides the basic operations of the separation/recovery of $CO_2$ (pre-combustion capture) from a fuel gas ($CO_2/H_2$) mixture.