• 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.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.156-168
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• 2013

Drilling expedition #1 in 2007 and drilling expedition #2 in 2010 were performed for gas hydrate resources evaluation and optimal site selection of pilot test in Ulleung basin, East Sea, Korea. This study presents to build the 3D spatial distribution models using the estimated sedimentary facies, porosity, and gas hydrate saturation derived by well logs and core analysis data from UBGH1-4, UBGH1-9, UBGH1-10, UBGH1-14, UBGH2-2-1, UBGH2-2-2, UBGH2-6, UBGH2-9, UBGH2-10 and UBGH2-11. The objective of 3D spatial distribution modeling is to build a geological representation of the gas hydrate-bearing sediment that honors the heterogeneity in 3D grid scale. The facies modeling is populating sedimentary facies into a geological grid using sequential indicator simulation. The porosity and gas hydrate saturation modeling used sequential Gaussian simulation to populate properties stochastically into grid cells.

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

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.133-140
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• 2009

This paper presents the experimental study to analyze the pressure and production behavior using depressurization and thermal methods in order to evaluate the hydrate productivity in the 2-D multi-well, plate-type apparatus which has 80 md permeability and 30% hydrate saturation. Injecting methane gas through multi-well allowed to set up the highly saturated hydrate system and combining two different sorts of sands made possible to build up the low permeability system. In this system, both depressurization and electric stimulation methods were applied. When operating pressure was low, according to the depressurization experiments results, the gas recovery was high, however strong pulses which appeared at initial stage of production would damage the operation system. Moreover, cases that hydrate reformed have occurred by endothermic reaction. We have conducted experiments four and six times for the depressurization magnitudes of 140 psi and 320 psi, respectively, to analyze production behavior for the method more in detail. For the cases that the depressurization magnitude was set as 140 psi, the unstable period appears in the results, but stabilized soon. In the experiment results for 320 psi the discontinuous and intermittent behavior has been observed. Thermal stimulation experiments was conducted with depressurizing 80 psi which is the case that shows stable behavior and low recovery. In the results, the gas recovery was high and the energy efficiency was low for long stimulating time. The energy efficiency and gas recovery increased for the soaking time of 1 minute after 2 minute-preheating. In the cases of which the soaking time exceeds 1 minute, energy loss by long soaking time caused low gas recovery and poor energy efficiency.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.304-309
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• 2007

In this study, the "Multi Well Plate-type cell Apparatus" was designed and setup for performing the producing experiments of methane hydrate by depressurization, heat stimulating methods. In order to characterizing the producing mechanism of hydrate through porous materials, the experiments for various producing methods have been conducted with the aid of the apparatus which has high permeability. In the experimental result of depressurization method, the pressure is temporarily increased unlikely conventional gas reservoir due to the sourcing effect of hydrate dissociation in the pore. Meanwhile, the temperature is decreased because of the endothermic reaction while hydrate is dissociated. In the experimental results of heat stimulating method, the dissociation in depressurization method is more slowly processed than that in thermal method, and hence, its gas production is lower. In the case of production right after heating, hydrate is dissociated only near injecting point and the permeability becomes greater at that area only. It infers that the more gas is produced during relatively earlier producing period. Since then, the hydrate is more slowly dissociated than the case of production after heating and soaking. This time, the performances of pressure and production obtained by thermal method have been analyzed in order to investigate the effect of soaking time on gas recovery. As a result, the gas recoveries in the case of 2 min and 4 min soaking are higher than case in 6 min soaking. This is reason that hydrate is reformed due to the decrease of temperature. It is expected that the experimental results obtained in this work may be more clearly explained by utilizing the lower permeable porous system with the greater hydrate saturation.