• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.102-115
• /
• 2014

In the Ulleung basin in the East Sea of Korea, it is assumed that huge amounts of gas hydrate(GH) are buried. In 2010, drilling operation was performed at the 2nd Ulleung Basin Gas Hydrate Drilling Expedition(UBGH2) to designate a site for field production test. In this study, based on the field production test site model reflecting geological properties, GH dissociation flow interpretation is analyzed and sensitivity analysis is performed to gain understanding of production behavior properties following bottomhole pressure(BHP) variation by using the numerical simulation. The results of this study provide a basis for the preliminary analysis of field production test site.

• Tunnel and Underground Space
• /
• v.24 no.2
• /
• pp.143-154
• /
• 2014

In this study, we simulated both dissociation of gas hydrate and mechanical deformation of hydrate-bearing sedimentary formation using geomechanical model. The geomechanical model analysis consists of two distinct codes of TOUGH+Hydrate and FLAC3D. The model is characterized by the fact that changes of temperature, pressure, saturation and their influence on the consequent evolution of effective stress, stiffness and strength of hydrate-bearing sediments during gas production could be well simulated. We compared the results of simulation for two different production methods, and showed that combination of depressurization and thermal stimulation results in the enhancement of production rate especially at early stage. We also presented that the hydrate dissociation-induced geomechanical deformation in unconsolidated clay is much larger than that in sandstone.

• Geophysics and Geophysical Exploration
• /
• v.12 no.3
• /
• pp.255-262
• /
• 2009

Conventionally, vertical-seismic-profiling (VSP) survey that provides high-resolution information has mainly performed to obtain the exact depth of the gas hydrate-bearing sediment, which is one of the key factors in the development of the gas hydrate. In this study, we extracted interval velocities and created corridor stacks from the first domestic zero-offset VSP data, which were acquired with three component receivers at UBGH09 borehole in Ulleung Basin where gas hydrate exists. Then we compared the corridor stacks with a CMP stacked section from surface seismic data. First of all, we converted the signals recorded with three component receivers to true vertical and horizontal components by phase rotation, and divided the data into direct waves and reflected waves by wavefield separation processing. The trend of the interval velocity extracted from the zero-offset VSP was similar to that of the sonic log obtained at the same borehole. Because the interval velocity of the gas hydrate-bearing sediment above the BSR was high, and it decreased suddenly through the BSR, we could infer that free gas is accumulated below the BSR. The results of comparing the corridor stacks to the CMP stacked section of the surface seismic data showed that most reflection events agreed well with those in the surface CMP stacked section and that the phase-rotated VSP data corresponded better with the surface seismic data than the VSP data without phase rotation. In addition, by comparing a corridor stack produced from the transverse component with the CMP stacked section of the surface seismic data, we could identify PS mode-converted reflections in the CMP stacked section.

• Journal of Energy Engineering
• /
• v.21 no.1
• /
• pp.55-67
• /
• 2012

For the development of gas hydrate as new future energy resources, the drilling was carried out at the five locations where have high potential as gas hydrate bearing sediments in Ulleung basin, offshore Korea in 2007. Well log data were obtained from all wells and core data were procured from 3 wells, UBGH1-04, UBGH1-09 and UBGH1-10. In this study, user-friendly software, "KMU GH Logs 2010", is developed and this software is based on the estimation methods developed in previous study for gas hydrate bearing sediments and the properties estimated from UBGH1-04, UBGH1-09 and UBGH1-10. Petrophysical properties in un-cored wells, UBGH1-01 and UBGH1-14, are also estimated by using well log data. Porosity is estimated by density log and gas hydrate saturation is calculated by sonic log and resistivity log. Sedimentary facies are estimated by applying the linear discriminant analysis using both well log and sedimentary facies data from core analysis. It is confirmed that DITM facies and MSS facies appeared signs of gas hydrate disassociation are able to be distinguished by the method.

• Tunnel and Underground Space
• /
• v.25 no.2
• /
• pp.133-143
• /
• 2015

Gas hydrate is a solid substance composed of natural gas constrained in water molecules under low temperature and high pressure conditions. The existence of hydrates has been reported to be world-widely distributed, mainly at permafrost and deep ocean floor. Test productions of small amount of natural gas from the on-shore permafrost have been accomplished in U.S.A and Canada, but, world-first and the only production case from off-shore hydrate bearing sediments was in Nankai trough, Japan. In this study, we introduce key technologies in gas production from hydrates by analyzing the Japanese off-shore gas production project in Nankai trough in terms of depressurization- induced dissociation so as to utilize planned domestic gas production test in Ulleung basin.

• The Korean Journal of Petroleum Geology
• /
• v.7 no.1_2 s.8
• /
• pp.13-18
• /
• 1999

Methane hydrate is an ice-like solid material and it has a structure which water molecules enclose gas molecules. For low temperature and high pressure, hydrocarbon gas forms hydrate and due to this condition, it is existed in the arctic region or deep sea. Presently, the amount of methane hydrate is unpredictable, but it is assumed that the amount will be enormous. For this reason, it is expected that it will play a major role as natural gas resources in the future. However, the production technologies are stayed on the low level and the economical technology was not developed yet. Also, emission of natural gas from methane hydrate will cause global warming and thus it is considered as a critical environmental problem. In this paper, the state of the art of the production technologies and environmental effects of methane hydrate were summarized.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.5
• /
• pp.407-412
• /
• 2014

A new apparatus for seawater desalination, based on the principle of gas hydrates, is suggested. The equipment continuously produces and pelletizes gas hydrates by a squeezing operation in a dual cylinder unit, which is able to extract pure hydrate pellets from the seawater-containing reactor. Desalination efficiency for each dissolved ion from seawater samples was tested by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC) analysis. This study demonstrates that the suggested method and the stated apparatus may solve the difficulty of separating hydrate crystals from concentrated brine solutions, and therefore may be applied to improve the efficiency of existing desalination processes.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.9
• /
• pp.973-980
• /
• 2015

With their wide geographical distribution, unconventional resources are continuously compared against conventional resources, but their development is expanding because TRRs (Technical Recoverable Resources) are similar to conventional resources. In particular, there is active development of unconventional gas resources such as shale gas, tight gas, CBM (coalbed methane) and gas hydrate. However, it is difficult to calculate the material properties of unconventional resources, especially the gas content, with current geophysical logging technology. Additionally, some overseas companies have monopolies on related equipment and materials. Therefore, this study developed a reservoir PCS (Pressure Core Sampler). It can collect core samples without gaseous loss by maintaining high pressure from the moment the core is sampled and record pressure and temperature in real time. Successful performance testing was also carried out for official verification of the manufactured PCS. The reservoir PCS will contribute to the acquisition of geophysical well logging data as well as accurate and reliable cores.

• Journal of the Korean Institute of Gas
• /
• v.24 no.5
• /
• pp.56-64
• /
• 2020

This study presents the hydrate induction time of PVCap according to subcooling temperature, salt concentration, and MEG concentration in order to analyze the inhibition effect of PVCap in various production environments of offshore gas fields. A high-pressure hydrate generator was made for the hydrate formation experiments. It was verified that the apparatus had sufficient reliability by comparing the results of hydrate equilibrium conditions and induction time from the apparatus with published reference data. As the subcooling temperature increased from 6.1℃ to 12.1℃, the induction time of PVCap concentration of 0.1~1 wt% decreased. When the salt concentration increased from 3 wt% to 7 wt%, the induction time was reduced by up to 78% under the condition of 0.5 wt% PVCap due to polymer structure degradation by salt effect. In the case of HHI (hybrid hydrate inhibitor) made by mixing MEG 10 wt% and PVCap, the change in induction time was not large compared to PVCap 1 wt% due to the under-inhibition effect. On the other hand, the hydrate inhibition efficiency of HHI with MEG 20wt% increased 1.7 times compared to PVCap.

• Resources Recycling
• /
• v.16 no.1 s.75
• /
• pp.37-43
• /
• 2007

It was studied to prepare anhydrous magnesium chloride which could used as the raw material of a fused salt electrolysis of magnesium by dehydration of magnesium chloride hydrate. The dehydration was carried out in a tube furnace at $350{\sim}580^{\circ}C$. It was confirmed that magnesium chloride hydrate was oxdized to magnesia through the dehydration in ambient atmosphere, but anhydrous magnesium chloride could be obtained in hydrogen chloride gas atmosphere. And the crystallity of the product increased with increasing temperature and time of dehydration. All of the un-reacted hydrogen chloride gases which were generated during the dehydration in hydrogen chloride gas atmosphere could be recovered as hydrochloric solution, and it could be reused for chlorination of magnesia to prepare magnesium chloride hydrate.