• The Journal of the Acoustical Society of Korea
• /
• v.28 no.5
• /
• pp.424-431
• /
• 2009

This study investigates the difference of sound velocity (compressional wave velocity) between gas hydrate-bearing sediments and nongas hydrate-bearing sediments in the Ulleung Basin, East Sea. We use a dataset measured from one site in the central part of the Ulleung Basin. Sound velocity for gas hydrate-bearing sediment shows the range from 1600 m/s to 2200 m/s. However, the value for nongas hydrate-bearing sediment is mostly around 1500 m/s, being less than 1400 m/s below 140 m subbottom depth. This trend is probably due to the presence of free gas below BSR (Bottom Simulating Reflector). Gas hydrate-bearing sediments show high value (maximum 150 Ohm-m) of resistivity. The physical properties between gas hydrate-bearing sediment and nongas hydrate-bearing sediment are characterized by the different patterns due to the presence of gas hydrate in comparison with those of marine unconsolidated sediments. Therefore, in order to investigate acoustic and physical properties for gas hydrate-bearing sediments, the study for the occurrence type and the amount of gas hydrates should be conducted simultaneously.

• Economic and Environmental Geology
• /
• v.47 no.3
• /
• pp.275-289
• /
• 2014

Recent scaled-up onshore and offshore field production tests revealed that the expectancy to produce gas from the gas hydrate deposits is gradually increasing, recognizing its potentials as one of the future energy resources. The total produced gas was approximately $480m^3$ by the hot water circulation method for 6 days' operation in Mallik 2002 project in Canada. In Mallik 2006-2008 project, the gas was successfully produced stably by the depressurization method for 6 days, up to $13,000m^3$ cumulatively. The depressurization method applied in the Mallik test was revealed as an effective way to produce gas from gas hydrates. The Alaska North Slope field trial in 2012 to inject mixed gas of $CO_2$ and $N_2$ to exchange $CH_4$ was successfully completed for the first time to produce maximum $1,270m^3$ per day. The remarkable achievement is that Japan has completed first offshore production test in the Eastern Nankai Trough, and produced approximately $120,000m^3$ of methane by the depressurization method for 6 days in March 2013. The technical challenges and uncertainties obtained from Nankai Trough production test give Korea more considerations in the aspects of well completion, reservoir formation and seafloor stability, sand control, flow assurance, and etc., due to the different geological environments and geomechnical properties in Ulleung Basin in Korea.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.638-642
• /
• 2005

For gas hydrate exploration, long offset multichannel seismic data acquired using by the 4km streamer length in Ulleung basin of the East Sea. The dataset was processed to define the BSRs (Bottom Simulating Reflectors) and to estimate the amount of gas hydrates. Confirmation of the presence of Bottom Simulating reflectors (BSR) and investigation of its physical properties from seismic section are important for gas hydrate detection. Specially, faster interval velocity overlying slower interval velocity indicates the likely presences of gas hydrate above BSR and free gas underneath BSR. In consequence, estimation of correct interval velocities and analysis of their spatial variations are critical processes for gas hydrate detection using seismic reflection data. Using Dix's equation, Root Mean Square (RMS) velocities can be converted into interval velocities. However, it is not a proper way to investigate interval velocities above and below BSR considering the fact that RMS velocities have poor resolution and correctness and the assumption that interval velocities increase along the depth. Therefore, we incorporated Migration Velocity Analysis (MVA) software produced by Landmark CO. to estimate correct interval velocities in detail. MVA is a process to yield velocities of sediments between layers using Common Mid Point (CMP) gathered seismic data. The CMP gathered data for MVA should be produced after basic processing steps to enhance the signal to noise ratio of the first reflections. Prestack depth migrated section is produced using interval velocities and interval velocities are key parameters governing qualities of prestack depth migration section. Correctness of interval velocities can be examined by the presence of Residual Move Out (RMO) on CMP gathered data. If there is no RMO, peaks of primary reflection events are flat in horizontal direction for all offsets of Common Reflection Point (CRP) gathers and it proves that prestack depth migration is done with correct velocity field. Used method in this study, Tomographic inversion needs two initial input data. One is the dataset obtained from the results of preprocessing by removing multiples and noise and stacked partially. The other is the depth domain velocity model build by smoothing and editing the interval velocity converted from RMS velocity. After the three times iteration of tomography inversion, Optimum interval velocity field can be fixed. The conclusion of this study as follow, the final Interval velocity around the BSR decreased to 1400 m/s from 2500 m/s abruptly. BSR is showed about 200m depth under the seabottom

• Geophysics and Geophysical Exploration
• /
• v.10 no.1
• /
• pp.37-43
• /
• 2007

The MH21 Research Consortium has conducted a high-resolution 3D seismic survey and a seafloor geochemical survey, to explore methane hydrate reservoirs in the eastern Nankai Trough, offshore Japan. Excellent geological information about shallow formations was obtained from the high-resolution 3D seismic survey, which was designed to image the shallow formations where methane hydrates exist. The information is useful in constructing a geological and geochemical model, and especially to understand the complex geology of seafloor, including geochemical manifestations and the structure of migration conduits for methane gas or methane-bearing fluid. By comparing methane seep sites observed by submersibles with seismic sections, some significant relationships between methane hydrate reservoirs, free gas accumulations below the seafloor, and seafloor manifestations are recognised. Bathymetric charts and seafloor reflection amplitude maps, constructed from seismic reflections from the seafloor, are also useful in understanding the relationships over a vast area. A new geochemical seafloor survey targeted by these maps is required. The relationships between methane hydrate reservoirs and seafloor manifestations are becoming clearer from interpretation of high-resolution 3D seismic data. The MH21 Research Consortium will continue to conduct seafloor geochemical surveys based on the geological and geochemical model constructed from high-resolution 3D seismic data analysis. In this paper, we introduce a basis for exploration of methane hydrate reservoirs in Japan by fusion of 3D seismic exploration and seafloor geochemical surveys.

• Korean Chemical Engineering Research
• /
• v.51 no.4
• /
• pp.500-505
• /
• 2013

In this study, we investigated the kinetics of gas hydrate formation in the presence of ionic liquid (IL). Hydroxyethyl-methyl-morpholinium chloride (HEMM-Cl) was chosen as a material for the promotion effect test. Phase equilibrium curve for $CH_4$ hydrate with aqueous IL solution was obtained and its induction time and consumed amount of $CH_4$ gas were also measured. Aqueous solutions containing 20~20,000 ppm of HEMM-Cl was prepared and studied at 70 bar and 274.15 K. To compare the measured results to those of the conventional promoter, sodium dodecyl sulfate was also tested at the same condition. Result showed that the hydrate equilibrium curve was shifted toward higher pressure and lower temperature region. In addition, the induction time on $CH_4$ hydrate formation in the presence of IL was not shown. The amount of consumed $CH_4$ was increased with the whole range of tested concentration of IL and the highest consumption of $CH_4$ happened at 1,000 ppm of HEMM-Cl. HEMM-Cl induced and enhanced the $CH_4$ hydrate formation with a small amount of addition. Obtained result is expected to be applied for the development of technologies such as gas storage and transport using gas hydrates.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.11a
• /
• pp.13-14
• /
• 2015

Carbonation is the results of the interaction of carbon dioxide gas in the atmosphere with the alkaline hydroxides in the concrete. in other words, of the hydrates in the cement pastes, the one which reacts with readily is Ca(OH)₂, the product of the reaction being CaCO₃ and which decreases the alkalinity of concrete. Consequently, RC structure is deteriorated due to steel corrosion in concrete. As the importance of maintenance of reinforced concrete structure recently has emerged, the attention of durability of structure has been increasing. There are many studies about durability decline especially due to the carbonation. In order to study carbonation progress after surface repair of carbonated concrete, each carbonation penetration velocity from different repair materials of concrete structure is compared through the experiment of carbonation accelerating CO₂ concentration to 100%. As carbonation infiltration progress is predicted through this study, the counterplan of service life evaluation will be prepared on selection of repair materials of concrete structure.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.691-694
• /
• 2009

TBAB (Tetra-n-butyl ammonium bromide)는 상압에서 semi-clathrate를 형성하는 물질로서 최근 열역학적 촉진제 및 기체 저장 물질로서 주목받고 있다. 본 연구에서는 가스 하이드레이트 형성 시TBAB가 열역학적 촉진제로서 미치는 영향을 알아보기 위해 다양한 농도 (5, 10, 40, 60 wt%)의 TBAB를 $CH_4\;+\;H_2O$계, $CO_2\;+\;H_2O$계, $N_2\;+\;H_2O$계에 첨가하여 가스 하이드레이트 3상 평형 (H - LW - V)을 측정 하였다. 실험 결과 TBAB의 조성에 따른 촉진경향은 각 계가 유사하지만, 촉진 정도는 $N_2\;+\;H_2O$ 계가 앞의 두계에 비해 월등히 큰 것을 알 수 있었다. 또한, TBAB 농도가 40 wt% 일때 촉진효과가 가장 크게 나타났으며, 그 이상의 농도에서는 반대로 촉진효과가 감소하는 것을 알 수 있었다. 이는 혼합 하이드레이트 형성에 참여하지 못한 TBAB가 가스 하이드레이트 형성을 억제하기 때문으로 사료된다. 결과적으로 가스하이드레이트 공정에 TBAB를 열역학적 촉진제로서 적용할 경우 촉진효과가 가장 큰 40 wt% 범위의 농도로 사용하는 것이 가장 적절할 것으로 사료된다. 본 실험에서 얻어진 결과는 가스 하이드레이트 형성을 이용한 천연가스 수송/저장법을 위한 연구뿐만 아니라 기체 분리 공정 개발과 관련된 연구의 중요한 기초 자료가 될 것이다.

• Journal of Environmental Science International
• /
• v.29 no.6
• /
• pp.605-612
• /
• 2020

To improve the initial strength and stability of lightweight-foamed concrete, which shows suitable sound absorption and insulation characteristics, the effect of CO₂-reduced cement on the properties of the concrete was investigated. Various mixing ratios were applied by substituting a certain amount of slag and Calcium Sulfo Aluminate (CSA) in CO₂-reduced Ordinary Portland Cement (OPC) and the physical properties of the samples were examined using the Korean Standard. The kiln temperatures of the CSA were 100-200℃ ; these values are lower than those of OPC and can lead to energy saving. In addition, the low limestone content reduces greenhouse gas emissions by 20 %. Adding a small amount of CSA in OPC content activates Ca-Al-H₂-based hydrates, and the initial compressive strength of the concrete is improved. As the CSA content increased, the thermal conductivity of the concrete decreased by up to 8% compared to plain concrete, thus indicating an improvement in its insulation. Therefore, the settlement stability was improved as the addition of CSA shortened the setting time.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.545-548
• /
• 2009

최근 천연가스 개발의 중요성이 대두되면서 심해저 퇴적층에 존재하고 있는 천연가스 하이드레이트 개발에 많은 연구가 진행되고 있다. 본 연구에서는 심해저 퇴적층에 부존하는 가스 하이드레이트 조건과 유사하게 하기위해 3 wt% 농도의 염수를 다공성 실리카 젤 기공에 넣어 사용하였다. 기공의 직경에 따른 영향을 알아보기 위해 기공 직경이 각각 6.0, 15.0, 30.0 nm인 실리카 젤을 사용하여, 천연가스 주성분인 에탄, 프로판, 메탄+프로판 하이드레이트의 3상 (H-Lw-V) 평형을 측정하였다. 그 결과 기공의 크기가 작아질수록 각각의 벌크 상태의 에탄, 프로판, 메탄+프로판 하이드레이트에 비해 하이드레이트의 평형조건이 온도는 낮아지고 압력이 높아지는 저해효과가 커짐을 알 수 있었다. 실험값으로 부터 기공 내의 물과 하이드레이트상 사이의 계면장력 값을 Gibbs-Thomson식에 의해 구할 수 있으며, 열역학 계산을 통하여 실험값과 비교하였다. 본 연구에서 얻어진 결과는 심해저 천연가스 개발, 이산화탄소 심해저장 등의 가스 하이드레이트 응용 연구에 유용한 기초 자료가 될 것이다.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.182-185
• /
• 2008

최근 새로운 천연가스 수송/저장법으로 가스 하이드레이트 형성법이 주목받고 있다.본 연구에서는 천연가스의 저장 매체로 다공성 매질인 실리카 젤을 사용하였다. 다공성 실리카 젤을 사용할 경우 물과 기체의 접촉면적을 극대화 시킬 수 있어 가스하이드레이로의 전환율을 높일 수 있다. 본 연구에서는 천연가스 주성분인 에탄과 프로판 기체를 사용하였으며, 기공의 직경이 각각 6.0 nm, 15.0 nm, 30.0 nm, 100.0 nm의 다공성 실리카 젤을 사용하였다. 에탄은 270 $\sim$ 285 K의 온도범위와 9 $\sim$ 25 bar의 압력범위, 프로판은 260 $\sim$ 280 K의 온도범위와 1.8 $\sim$ 2.8 bar의 압력범위에서 기공 크기의 분포를 고려하여 하이드레이트(H)-물($L_W$)-기상(V)의 3상 평형점을 측정하였다. 측정 결과 기공의 크기가 작아질수록 각각의 벌크 상태의 에탄 및 프로판 하이드레이트에 비해 하이드레이트의 평형조건이 온도는 낮아지고 압력이 높아지는 저해효과가 커짐을 알 수 있었다. 천연가스 수송/저장으로서 응용을 고려할 경우 저해효과가 적은 100.0 nm이상의 다공성 실리카 젤을 사용하는 것이 적절할 것으로 사료된다. 본 연구에서 얻어진 결과는 천연가스 수송/저장뿐만 아니라 심해저 천연가스 개발, 이산화탄소 심해저장 등의 가스 하이드레이트 용용 연구에도 유용한 기초 자료가 될 것이다.