미세직경 얼음을 이용한 CO2 하이드레이트 제조특성 연구

이종협 ( Jong Hyub Lee ),강성필 ( Seong Pil Kang ) 한국화학공학회 2012 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.50 No.4

Gas hydrate is an inclusion compound consisting of water and low molecular weight gases, which are incorporated into the lattice structure of water. Owing to its promising aspect to application technologies, gas hydrate has been widely studied recently, especially CO2 hydrate for the CCS (Carbon Capture and Storage) issue. The key point of CO2 hydrate technology for the CCS is how to produce gas hydrate in an efficient and economic way. In this study, we have tried to study the characteristic of gas hydrate formation using micro-sized ice through an ultrasonic nozzle which generate 2.4 MHz frequency wave. CO2 as a carrier gas brings micro-sized mist into low-temperature reactor, where the mist and carrier gas forms CO2 hydrate under -55˚C and atmospheric pressure condition and some part of the mist also remains unreacted micro-sized ice. Formed gas hydrate was average 10.7 of diameter at average. The starting ice particle was set to constant pressure to form CO2 hydrate and the consumed amount of CO2 gas was simultaneously measured to calculate the conversion of ice into gas hydrate. Results showed that the gas hydrate formation was highly suitable because of its extremely high gas-solid contact area, and the formation rate was also very high. Self-preservation effect of CO2 hydrate was confirmed by the measurement of CO2 hydrate powder at normal and at pressed state, which resulted that this kind of gas storage and transport could be feasible using CO2 hydrate formation.

Gas trasport and Gas hydrate distribution characteristics of Southern Hydrate Ridge: Results from ODP Leg 204

이영주(Lee, Young-Joo),류병재(Ryu, Byong-Jae),김지훈(Kim, Ji-Hoon),이상일(Lee, Sang-Il) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06

Geochemical analyses carried out on samples collected from cores on and near the southern smit of Hydrate Ridge have advanced understanding by providing a clear contrast of the two major modes of marine gas hydrate occurrence. High concentrations (15%-40% of pore space) of gas hydrate occurring at shallow depths (0-40 mbsf) on and near the southern summit are fed by gas migrating from depths of as much as 2km within the accretionary prism. This gas carries a characteristic minor component of C2-C5 thermogenic hydrocarbons that enable tracing of migration pathways and may stabilize the occurrence of some structure II gas hydrate. A structure II wet gas hydrate that is stable to greater depths and temperatures than structure I methane hydrate may account for the deeper, faint second bottom simulating reflection (BSR2) that occurs on the seaward side of the ridge. The wet gas is migrating In an ash/turbidite layer that intersects the base of gas hydrate stability on the seaward side of and directly beneath the southern summit of Hydrate Ridge. The high gas saturation (>65%) of the pore space within this layer could create a two-phase (gas + solid) system that would enable free gas to move vertically upward through the gas hydrate stability zone. Away from the summit of the ridge there is no apparent influx of the gas seeping from depth and sediments are characterized by the normal sequence of early diagenetic processes involving anaerobic oxidation of sedimentary organic matter, initially linked to the reduction of sulfate and later continued by means of carbonate reduction leading to the formation of microbial methane.

Study of Producing Natural Gas From Gas Hydrate With Industrial Flue Gas

서유택(Yutaek Seo),강성필(Seong-Pil Kang),이재구(Jae Goo Lee),Min Jun Cha,Huen Lee 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.10

There have been many methods for producing natural gas from gas hydrate reservoirs in permafrost and sea floor sediments. It is well knownthat the depressurization should be a best option for Class 1 gas hydrate deposit, which is composed of tow layers: hydrate bearing layer and an underlying free gas. However many of gas hydrate reservoirs in sea floor sediments are classified as Class 2 that is composed of gas hydrate layer and mobile water, and Class 3 that is a single gas hydrate layer. The most appropriate production methods among the present methods such as thermal stimulation, inhibitor injection, and controlled oxidation are still under development with considering the gas hydrate reservoir characteristics. In East Sea of Korea, it is presumed that the thick fractured shale deposits could be Class 2 or 3, which is similar to the gas hydrate discovered offshore India. Therefore it is needed to evaluate the possible production methods for economic production of natural gas from gas hydrate reservoir. Here we would like to present the production of natural gas from gas hydrate deposit in East Sea with industrial flue gases from steel company, refineries, and other sources. The existing industrial complex in Gyeongbuk province is not far from gas hydrate reservoir of East Sea, thus the carbon dioxide in flue gas could be used to replace methane in gas hydrate. This approach is attractive due to the suggestion of natural gas productionby use of industrial flue gas, which contribute to the reduction of carbon dioxide emission in industrial complex. As a feasibility study, we did the NMR experiments to study the replacement reaction of carbon dioxide with methane in gas hydrate cages. The in-situ NMR measurement suggeststhat 42% of methane in hydrate cages have been replaced by carbon dioxide and nitrogen in preliminary test. Further studies are presented to evaluate the replacement ratio of methane hydrate at corresponding flue gas concentration.

Drilling Gas Hydrate at Hydrate Ridge, ODP Leg 204

이영주(Lee, Young-Joo),류병재(Ryu, Byong-Jae),김지훈(Kim, Ji-Hoon),이상일(Lee, Sang-Il) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately 300times500m area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

Geotechnical properties of gas hydrate bearing sediments

김학성(Kim, Hak-Sung),조계춘(Cho, Gye-Chun),이주용(Lee, Joo-Young) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.05

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.

Isostructural and cage-specific replacement occurring in sII hydrate with external CO₂/N₂ gas and its implications for natural gas production and CO₂ storage

Seo, Young-ju,Park, Seongmin,Kang, Hyery,Ahn, Yun-Ho,Lim, Dongwook,Kim, Se-Joon,Lee, Jaehyoung,Lee, Joo Yong,Ahn, Taewoong,Seo, Yongwon,Lee, Huen Elsevier 2016 APPLIED ENERGY Vol.178 No.-

<P>A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII hydrates significantly differs from that in sI hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8 + CH4) hydrate by externally injecting CO2/N-2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8 + CH4 hydrate with CO2/N-2 gas injection, indicating that sll hydrate decomposition followed by sI hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8 + CH4 hydrate revealed that CH4 replacement with N-2 in the small cages of slI was more significant than C3H8 replacement with CO2 in the large cages of sII. The total extent of the replacement for the C3H8 + CH4 hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4 hydrate with CO2/N-2 gas, the lower extent of the replacement for the C3H8 + CH4 hydrate with CO2/N-2 gas was attributable to the persistent presence of C3H8 in the large cages and the lower content of N-2 in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8 + CH4 hydrate with external CO2/N-2 gas will have significant implications for suggesting target gas hydrate reservoirs and understanding the precise nature of guest exchange in gas hydrates for both safe natural gas production and long-term CO2 sequestration. (C) 2016 Elsevier Ltd. All rights reserved.</P>

An application of rock physics modeling to quantify the seismic response of gas hydrate-bearing sediments in Makran accretionary prism, offshore, Pakistan

Muhammed Irfan Ehsan,Nisar Ahmed,Perveiz Khalid,Liu Xue Wei,Mustansar Naeem 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.3

Naturally occurring gas hydrates are potential future energy source. A significant amount of gas hydrates is interpreted through seismic reflection data in the form of bottom simulating reflector (BSR) present in the sediments of the convergent continental margin of Pakistan. However, the seismic character of these hydratebearing unconsolidated sediments is not properly investigated. Since no direct measurements are available for quantitative estimation of gas hydrate and free gas in these sediments, therefore detailed knowledge of seismic velocities is essential. Seismic velocities of the gas hydrate-bearing sediments in the study area are estimated by using the effective medium theory and the fluid substitution modeling. The results show that the presence of gas hydrates increases the stiffness of the unconsolidated sediments; whereas the presence of free gas decreases the stiffness of these sediments. It is noted that seismic velocities and density of hydrate-bearing sediments are highly affected by saturation and distribution pattern of gas hydrates. The hydrate-bearing sediments seem to be characterized not only by high P-wave velocity (about 2800 m/s) but also by anomalously low S-wave velocity (about 850 m/s). As pure gas-hydrates have much higher seismic velocities than those of host sediments, presence of gas-hydrate increases the seismic velocities, whereas free-gas below the hydrate-bearing sediments decreases the velocities. Seismic reflection from the BSR exhibits a wide range of amplitude variation with offset characteristics, which depend upon the saturation and distribution of hydrates above and free gas below the BSR. We have also demonstrated that some attributes like acoustic and shear impedances, and AVO can be used as important proxies to detect gas hydrate saturation.

미래 에너지로서 가스 하이드레이트의 개관 및 물리/화학적 특성

차민준,민경원 한국자원공학회 2018 한국자원공학회지 Vol.55 No.6

본 논문에서는 미래 에너지로서 가스 하이드레이트를 이해하기 위해, 가스 하이드레이트의 구조, 물리/화학 적 특성, 생성 기원과 세계 분포, 매장량과 생산기법, 하이드레이트의 지구환경적 영향에 대해 논의하였다. 하이드레 이트의 구조에 대한 명확한 이해는 자연계에 매장된 하이드레이트의 특성 분석, 분포와 매장량 산출에 필수적일 것으 로 판단된다. 안정적인 에너지 회수를 위해 고려해야 할 하이드레이트의 물리/화학적 특성으로는 하이드레이트의 상 평형, 해리 엔탈피, 열전도도, 비열, 열확산도, 유체투과율 등이 있다. 하이드레이트의 물리/화학적 특성을 고려하여 개발된 생산기법으로는 감압법, 열자극법, 억제제 주입법, 맞교환기법이 있으며, 감압법이 현재까지 해상 및 육상 하 이드레이트에 대해 모두 시험생산에 적용된 유일한 기법이다. 또한, 하이드레이트의 해리에 따른 온실가스 배출에 의 한 지구환경적 영향의 가능성에 대해서도 고찰하였다. This paper reviews the structures, physical and chemical properties, origins and global distribution, amount of energy resources, production technologies, and environmental impacts of gas hydrates to understand the gas hydrates as future energy sources. Hydrate structures should be studied to clarify the fundamentals of natural gas hydrates, hydrate distributions, and amount of energy sources in hydrates. Phase equilibria, dissociation enthalpy, thermal conductivity, specific heat, thermal diffusivity, and fluid permeability of gas hydrate systems are important parameters for the the efficient recovery of natural gas from hydrate reservoirs. Depressurization, thermal stimulation, inhibitor injection, and chemical exchange methods can be considered as future technologies to recover the energy sources from natural gas hydrates, but so far depressurization is the only method to have been applied in test productions of both onshore and offshore hydrates. Finally, we discuss the hypotheses of environmental impacts of gas hydrates and their contribution to global warming due to hydrate dissociation.

가스하이드레이트 제조성능 향상을 위한 영향인자 검토 연구

신창훈(Chang Hoon Shin),김유나(Yu Na Kim),권옥배(Ok Bae Kwon),박승수(Seung Su Park),한정민(Jeong Min Han),이정환(Jeong Hwan Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

Gas hydrates are ice-like crystalline compounds that form under low temperature and elevated pressure conditions. Although hydrate formation can pose serious flow-assurance problems in the gas pipelines or facilities, gas hydrates present a novel means for natural gas storage and transportation with potential applications in a wide variety of areas. An important property of hydrates that makes them attractive for use in gas storage and transportation is their very high gas-to-solid ratio. In addition to the high gas content, gas hydrates are remarkably stable. The main barrier to development of gas hydrate technology is the lack of an effective method to mass produce gas hydrate in solid form. The first objective of this study is investigating the characteristics of gas hydrate formation related to several factors such as pressure, temperature, water-to-storage volume ratio, concentration of SDS, heat transfer and whether stirred or not respectively. And the second objective is clarifying the relation between the formation efficiency and each factor in order to find the proper way or direction to improve the formation performance.

가스하이드레이트 개발 국제 동향과 특허 분석

김대형,이재욱 한국자원공학회 2010 한국자원공학회지 Vol.47 No.4

Gas hydrates are solid crystalline compounds in which gas reside inside cages formed by hydrogen-bonded water molecules in a crystalline lattice. As the world wide estimated resources of gas hydrate is so huge (between 1016 to 1019 SCF), after 21 century, a lot of research work for the commercial use of gas hydrate is conducted. In this study, recent important gas hydrate R&D trends & programs were reviewed, and carried out several analyses on patent documents for techniques of gas hydrate exploration and production. The patents including abstracts, claims and drawings from 1975 up to 2008 were surveyed and 141 patents were collected finally. The patents were investigated as to countries, assignees, and techniques. As a result, we suggested implications for effective policy of patent application and management on gas hydrate. 천연가스가 저온, 고압 하에서 물 분자와 결합되어 형성된 고체 물질로 주성분이 메탄으로 구성되어 있는 가스하이드레이트는 국제적으로 광범위하게 분포된 부존과 막대한 매장량으로 인해 기존의 석유, 가스를 대체할 새로운 에너지원으로 국제적 관심을 받고 있다. 특히 2000년 대 중반 이후 석유 등 화석연료 가격이 폭등하면서 국제적으로 가스하이드레이트의 상업적 개발, 생산 및 이용을 위한 다양한 연구들이 이루어진 바 있다. 본고에서는 가스하이드레이트의 조사·탐사, 개발, 생산과 관련하여 국제적으로 이루어진 대표적인 연구 및 개발 프로젝트의 최근 동향을 살펴보았다. 또한 1975-2008년까지의 가스하이드레이트 조사·탐사, 개발·생산 및 안전성 관련 국내외 특허 141건을 분석하여, 국제적 기술 흐름의 추세와 함께 특허보유 국가 및 출원인을 분석하였으며, 향후 효과적인 특허 출원 및 관리를 위한 시준점을 제시하였다.