• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.515-522
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• 2007

In this study we have attempted to evaluate the technical feasibility of "BB-HY", which is depleted gas reservoir as a gas storage field, using the commercial compositional simulator "ECLIPSE 300". The "BB-HY" reservoir has an initial gas in place of 143 BCF which is relatively small, and its porosity and permeability are 19.5% and 50 md, respectively. For "BB-HY" gas reservoir, we have performed a feasibility analysis by investigating the cushion gas (or working gas), converting time to gas storage field, operation cycle, number of wells and the possible application of horizontal borehole as well. From the simulation results, it was found that the amount of cushion gas in "BB-HY" reservoir is required at least 50% of IGIP in order to operate stably as gas storage field. When one produces gas for longer time and hence the remaining gas in reservoir is less than optimal cushion gas, no technical problem was occurred as long as additional cushion gas is injected up to the optimal cushion gas. In the case of changing the operation cycle into producing gas for three months during winter season from producing five months, the result shows that either the cushion gas should be greater than 60% or the more number of wells should be drilled. Meanwhile, from the results of sensitivity analysis for the number of wells, in cases of operating six or eight vertical wells, the stable reproduction of the injected gas can not be possible in "BB-HY" gas reservoir since the remaining gas in reservoir is increased. Therefore, in "BB-HY" reservoir, at least ten vertical wells should be drilled for the stable operation of gas. This time, when three horizontal wells are additionally drilled including the existing two vertical wells, it was found that the operation of injection and reproduction of gas is relatively stable in "BB-HY" gas reservoir.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.638-647
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• 2007

In this study, we present the evaluation chart for assessing the applicability of $CO_2$ flooding method to oil reservoirs. The evaluation chart consists of four categories as source availability, miscibility, applicability and injecting method of miscible flooding. The applicability of reservoir and oil in the chart has basic items of the properties such as oil gravity, viscosity, oil saturation, reservoir temperature and permeability, and these are quantitatively graded. Meanwhile, for additional items of $CO_2$ purity, reservoir thickness and formation dip, they are graded as "highmediumlow". In the case of evaluating the injection method of either continuous injection or WAG ($CO_2$), the qualitative decision will be made according to formation dip, vertical permeability, reservoir thickness, etc. The recommended score in the chart was assigned by utilizing 51 oil producing fields which $CO_2$ flooding is successfully being applied. The evaluation chart developed in this work has been applied to the Captain oil producing field located in Scotland as well as to the Onado oil field of Venezuela, which Korean oil companies have participated in. For the Captain field, the reservoir quality in terms of permeability and porosity is considered to be very excellent to flow the oil. The oil in captain field contains heavier component of $C_{21+}$ as 54%. Therefore, this heavy oil could be immiscibly displaced, hence the evaluating result with the basis of immiscible criteria shows that $CO_2$ immiscible flooding in this field could be properly applied. In the case of Onado oil producing field, since the estimated minimum miscibility pressure is lower than the reservoir pressure, it was assessed that the Onado field would be efficiently conducted for $CO_2$ miscible flooding.

• Journal of Soil and Groundwater Environment
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• v.10 no.6
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• pp.32-44
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• 2005

314 pumping test data of the National Groundwater Monitoring Wells (NGMWs) are analyzed to present statistical properties of fractured-rock and alluvial aquifers of Korea such as distribution of hydraulic conductivity, empirical relations between transmissivity and specific capacity, and time-drawdown patterns of pumping and recovery test. The mean hydraulic conductivity of alluvial aquifers (1.26 m/day) is 17 times greater than that of fractured-rock aquifers (0.076 m/day). Hydraulic conductivity of fracture-rock aquifers ranges in value over 4 orders of magnitude which coincide with representative values of fractured crystalline rocks and shows distinctive differences among rock types with the lowest values for metamorphic rocks and the highest values for sedimentary rocks. In consideration of the estimated transmissivity with some simplifying assumptions, it Is likely that $32\%$ of groundwater flow for NGMWs would occur through fractured-rock aquifers and $68\%$ through alluvial aquifers. Based on 314 pairs of data, empirical relations between transmissivity and specific capacity are presented for both fractured-rock and alluvial aquifers. Depending on time-drawdown patterns during pumping and recovery test, NGMWs are classified into $4\~5$ types. Most of NCMWs $(83.7\%)$ exhibit the recharge boundary type, which call be attributed to sources of water supply such as streams adjacent to the pumping well, the vertical groundwater flux between fractured-rock and the alluvial aquifers, and the delayed yield associated with gravity drainage occurring in unconfined aquifers.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.1-19
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• 2004

Metallic deposits in Korea have a variety of genetic types such as hydrothermal veins, skarns, hydrothermal replacement and alaskite deposits and so on. Geological, mineralogical and geochemical features including host rock, wall-rock alteration, ore and gangue mineralogy, mineral texture and secondary mineralogy related to weathering process control the environmental signatures of mining areas. The environmental signatures of metallic deposits closed from early 1970s to late 1990s in Korea show complicate geochemistry and mineralogy due to step weathering of primary and secondary minerals such as oxidation-precipitation-remobilization. The potentiality of low pH and high heavy metal Concentration s from acid mine drainage is great in base-metal deposits associated with polymetallic mineralization, breccia-pipe type and Cretaceous hydrothermal Au veins with the amount of pyrite whereas skam, hydrothermal replacement, hydrothermal Cu and Au-Ag vein deposits are in low contamination possibility. The geoenvironmental models reflecting the various geologic features closely relate to disuibution of sulfides and carbonates and their ratios and finally effect on characteristics of environmental signatures such as heavy metal species and their concentrations in acid mine drainage.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.323-336
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• 2000

Ultramafic rocks in Choongnam area are mainly serpenitinites which are parent rock of talc and asbestos ore deposits. About 10 $^{\circ}$ NNE-trending parallel serpentinites masses occur as discontineous isolated lenticular intrusive bodies in Precambrian gneiss complex between Hongseong-Kwangcheon line and Onyang-Cheongyang line. The sizes of serpentinites vary from several centimeters to 1 kilometer in width and from several meters to 5 kilometers in length. The serpentinites show high SiO$_2$(39.99wt.% in average), MgO(38.46wt % in average), Cr(>1011ppm), Ni(>1660ppm), and Co(>80ppm). Most serpentinites contain serpentine more than 50%. Some serpentines contain original minerals such as olivine, pyroxene and chromite. Also, serpentinites body may contain a little serpentinized peridotite, and some talc and asbestos ore deposits. The original rocks of the serpentinites interpreted as Alpine type ultramafic rocks, and dunite and/or harzburgite which were originated from slightly depleted upper mantle(30${\sim}$40km deep), and emplaced in the crust through the large fault zones. It seems that main serpentinization from the original rocks was occurred during greenschist and/or amphibolite facies regional metamorphism in Choongnam area.

• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.629-641
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• 2006

The Standing Buddha Statue in the Gwanchoksa temple consists of medium to coarse grained biotite granodiorite with dark grey color, and it has a week gneissosity along the pegmatite veins. The results of magnetic susceptibility and geochemical patterns of the host rock of Standing Buddha Statue and the basement rock suggest that both values are formed from the co-genetic magma with the same differentiation process. The CIAs of the basement rock and the Standing Buddha Statue are calculated to 51.43 and 50.86, and the WPIs are estimated 4.52 and 8.95, respectively. So the weathering potential from the host rock of Standing Buddha Statue and basement rock prove to be high. The Standing Buddha Statue is terribly damaged with physical weathering from deterioration and exfoliation, and are scattered with secondary pollutant and precipitate. Basement rock is also in danger of ground collapse because of irregularly developed discontinuity system. Most surface of Standing Buddha Statue is seriously discolored into yellowish brown and dark gray, or black precipitates are also formed. Moreover, it is heavily covered with crustose lichen, fungi and algae, or moss are also found. In order to control the influential factors with the complex deterioration of Standing Buddha Statue, it is needed to rearrange a site environments, and conservation scientific management is required to protect it from covering lichens, exfoliations and fractures.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.67-81
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• 2015

A FORTRAN program was developed to determine the optimal locations of multiple recharge wells in an aquifer with different arrangements of pumping wells. The simulated annealing algorithm was used to find optimal locations of two recharge wells which satisfied three objective functions. The model results show that locating two injection wells inside the cluster of pumping wells is efficient if the recovery rate only was taken into account. In contrast, placing injection wells to the side of the cluster is desirable if the simulation considers aggregate objective function. Therefore, installing an injection well on each side of the cluster seems to yield the maximum recovery rates for the existing pumping wells, and it yields similar increases in pumping rate for all wells in the cluster. The locations of recharge wells can be arranged in numerous configurations, because there are multiple near-optimal local minima or maxima. These results indicate that the simulated annealing can yield effective evaluations of the optimal locations of multiple recharge wells. In addition, the suggested aggregate objective function can be utilized as an appropriate multi-objective optimization.

• Journal of agricultural medicine and community health
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• v.37 no.2
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• pp.76-83
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• 2012

Objectives: The purpose of this study was to define the underserved emergency medical services (EMS) areas in Daejeon metropolitan city, as well as to identify their distinctive characteristics in public health perspectives. Methods: An underserved EMS area was operationally defined as an area in which it is difficult to arrive at an emergency medical center within 30 minutes. Using a cost-weighted distance algorithm with a geographic information system (GIS), the underserved EMS area was calculated. The characteristics of the underserved areas were analyzed by the Chi-square test. The SPSS statistical software package was used to perform the statistical analysis. All statistical tests were two-sided, and a p-value<0.05 was considered statistically significant. Results: Twelve administrative sectors ('Dong' in Korean) were included in the underserved areas, accounting for a population of approximately 8,100 citizens. The relationships between underserved EMS area and populations of agriculture, fishery, and forestry; citizens who are recipients of national basic livelihood security program; disabled; or aged 65 or older were statistically significant. Conclusion: It was found that 12 administrative sectors were included in the underserved EMS areas. Revealing underserved EMS areas using GIS analysis based on a cost-weighted distance algorithm of road data was an effective analytic method. However, as this study was confined to Daejeon City, South Korea, a nation-wide study should be performed to provide a more accurate conclusion.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.141-153
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• 2016

The Manjang deposit is emplaced in Hwajeonri formation comprising limestone that is interbeded with slate and phyllite in the central Okcheon Group. It consists of the Main and the Central orebody of Cu-bearing hydrothermal vein deposit and the Western orebody of iron skarn deposit. Based on coexisting mineral assemblage the skarnization can be divided into prograde skarnization (stage I : clinopyroxene ${\pm}$ magnetite ${\pm}$ quartz, stage II : garnet + clinopyroxene ${\pm}$ magnetite ${\pm}$ quartz) and retrograde hydrothermal alteration (stage III: magnetite + amphibole + quartz ${\pm}$ garnet ${\pm}$ clinopyroxene ${\pm}$ chlorite ${\pm}$ epidote ${\pm}$ fluorite ${\pm}$ calcite, stage IV: fluorite ${\pm}$ pyrrhotite ${\pm}$ chalcopyrite ${\pm}$ amphibole ${\pm}$ quartz ${\pm}$ calcite). Diopside is abundant in stage I, and hedenbergite was produced in stage II and III. Garnet compositions change from grandite to andradite, which suggests a redox transition from relatively reduced to oxidized condition during the skarn formation. Magnetite in stage I and II has relatively constant Fe contents, while in the stage III it has increased Si and Ca concentrations. This variation could indicate that magnetite was more strongly affected by host rocks during the retrograde stage. Sulfur isotope compositions of pyrrhotite and chalcopyrite produced in stage IV are within the range of + 5.9~6.9 ‰, corresponding to igneous origin, but slightly high sulfur isotope values could be attributed to an interaction with host rocks, limestone.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.87-101
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• 2018

The Manjang deposit developed in the Hwajeonri formation of the Okcheon metamorphic belt consists of the Central and Main orebodies of Cu-bearing hydrothermal vein type and the Western orebody of Fe-skarn type. This study focuses on the Cu mineralization of the Central and Main orebodies to compare with the genetic environments of the Western orebody previously studied. The Central orebody produced pyrrhotite and chalcopyrite as major ore minerals with vein texture, while the Main orebody contains pyrite, arsenopyrite, and chalcopyrite as major ore minerals with vein, massive, and brecciated texture. Sphalerite, galena, magnetite, ilmenite, rutile, cassiterite, wolframite, and stannite are also accompanied. Local occurrence of skarn is dominated by grossular and hedenbergite, reflecting the reduced condition of the skarnization. Geothermometries of sphalerite-stannite in the Central orebody and arsenopyrite-pyrite in the Main orebody indicate the formation temperature of $204-263^{\circ}C$ and $383-415^{\circ}C$, respectively. Sulfur fugacity of $10^{-6}-10^{-7}atm$. in the Main orebody decreased toward the Central orebody. Sulfur isotope compositions of sulfide minerals from the Central and Main orebodies are 4.6-7.9‰ and 4.3-7.0‰, respectively, reflecting magmatic origin with slight influence by host rock. Considering ore mineralogy, texture as well as physicochemical conditions, the Main and Central orebodies of hydrothermal Cu mineralization reflect the characteristics of proximal and distal type ore mineralization, respectively, related to hidden igneous rocks, and they were generated under different hydrothermal systems from the Fe-skarn Western orebody.