• Geomechanics and Engineering
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• v.12 no.3
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• pp.465-481
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• 2017

Thermal effect has great influence on wellbore stability in Dongfang 1-1 (DF 1-1) gas field, a reservoir with high-temperature and high-pressure. In order to analyze the wellbore stability in DF1-1 gas field, the variation of temperature field after drilling was analyzed. In addition, the effect of temperature changing on formation strength and the thermal expansion coefficients of formation were tested. On this basis, a wellbore stability model considering thermal effect was developed and the thermal effect on fracture pressure and collapse pressure was analyzed. One of the main challenges in this gas field is the decreasing temperature of the wellbore will reduce fracture pressure substantially, resulting in the drilling fluid leakage. If the drilling fluid density was reduced, kick or blowout may happen. Therefore, the key of safe drilling in DF1-1 gas field is to predict the fracture pressure accurately.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.86-92
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• 2012

An exploration well is drilled where oil or gas potential is shown by a seismic survey and interpretation. With the advance of drilling technology, most of the easily accessible oil had been developed by the end of the 20th century. To satisfy the ever increasing demand for oil, and bolstered by high oil prices, the major oil companies started to drill in deep water, which requires a deep offshore drilling unit. Offshore drilling units are generally classified by their maximum operating water depth. Many semi-submersible rigs have been purpose-designed for the drilling industry as the allowable drilling water depth has become deeper by the developed technics since the first semi-submersible was launched in 1963. Semi-submersible rigs are commonly used for shallow to deep water up to 3,000 m. Drilling equipment such as a top drive, blowout preventer, drawworks and power system, mud circulation system, and subsea wellhead system are explained to help with an understanding of offshore drilling procedures in the oil and gas fields. The objective of this paper is to introduce the main components of a semi-submersible rig and, by doing so, to raise the awareness of offshore drilling, which accounts for over 30% of the total oil production and will continue to increase.

• Journal of the Korean earth science society
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• v.25 no.1
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• pp.1-9
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• 2004

The clay minerals of thirty-four bottom sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more-than 70% of whole clay fraction. The highest concentration of illite (>72%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Cheju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where the fine-grained sediments are discharged from the modern and ancient Huanghe River. The relatively high abundance of kaolinite is likely derived from the Changjiang River via Taiwan ·Warm Current. In contrast, the large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern are, reflecting the transportation by the Huanghai Sea Coastal Current from the southern Yellow Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.243-249
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• 2000

Seasonal variation in species composition and abundance of shallow water fish off Yongwon, Jinhae in the southern coast of Korea was determined by the analysis of monthly samples collected by a beach seine from January to December, 1998. Among 54 species identified, the resident species such as Favonigobius gymnauchen, Chaenogobius laevis, Pholis nebulosa and juvenile Hyporhamphus intermedius were predominated in abundance. The temporal species such as Sardinella zunasi, Leiognathus nuchalis and Takifugu niphobles were collected between April and September. Mean abundance (322 individuals/1000 $m^2$ or 806 g/1000 $m^2$) was higher than that in the shallow sand surf zone of Teachon, but lower than that in the shallow mud area of Chonsu Bay in the western coast of Korea. A large number of H. intermedius were collected in cold months between November and January. The dominant resident species began to be collected from february, and the number of species and biomass were increased until July. A small number of temporal species were collected and subsequently the abundance was low from August to October when high abundance was expected as in the other shallow waters by recruitment of a large number of juveniles of temporal species. The low abundance in these warm months seemed to be related to the water quality by weak water circulation in this shallow mud area.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.479-490
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• 2016

Seabed drilling system has recently been used to drill seafloor mineral resources. This case report highlights the procedure and result of sea-trial of seabed drilling system at off-shore of Japan on March, 2016 as well as briefs an international-technical trend of seabed drilling system. In case of having less than 100 m drill depth, seabed drilling system is favorable for seafloor mineral deposits which are mostly distributed within a narrow district and situated between 1000~3000 m water depth, compared with vessel-mounted drilling system. The system is featured by the remotely-operated drill gear, which has top drives, drill strings and mud system on it. The core samples are generally recovered to ship with seabed driller after a dive. In this sea-trail, recovery rate of core samples averagely shows about 55% and the recovered rocks mostly correspond to fresh and/or weak-altered basalt. In case of drilling hydrothermal ore deposit, the recovery rate would be lower than 55% because of the fragile nature of ores. Alternatively it is used to collect cutting chips through riser or bins in order to increase the recovery rates. Recently a reverse circulation method is taken considered to acquire the better cutting-chips. Three-leg type outrigger system and four-leg type leveling system are the competing landing-instruments of seabed drill system. However the landing efficiency using these gears has to be further monitored due to lack of case reports.

• Journal of the Korea Furniture Society
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• v.22 no.1
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• pp.72-81
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• 2011

These days, beds have been developed not as furniture to sleep in but Healthcare Furniture. The function of heating, non-electronic-waves and far-infrared rays have been added. Also, eco-friendly materials such as stone, mud, rubber and wood are combined to them together with the radiation-heating method using heat conduction through electronic coil and hot water circulation. Modern people suffer from stress and fatigue. The hot issue is "health." Focused on the health, the development of design for beds considering the influence electronic waves, anions, deep sleep and the density of toxic materials have on human bodies has become urgent. In this study, the trend, specification and efficiency of the functional health-related electronic coil technology are analyzed. Through the analysis, the environmental standards are set. According to them, technology, eco-friendly materials and additional functions for the development of the design are considered. Also, the government is promoting the IEC international standardization for the Korean traditional floor heating style beds. In preparation for that, we adopted new HPT method technology. It enables non-electronic-waves, low electricity and stable temperature maintenance control for the warm top and the cool bottom. Also, the head boards and the frames of the beds can be separated. Through this separation, the beds can be easily moved or installed. Eco-friendly materials such as Hinoki cypress wood and red clay and the existing tables function are combined to the head boards so they can be used as drawers and display shelves. If they are used as separate items, they can be used as covers. This is how we suggest the design for the heating beds.

• Journal of the Korea Society for Simulation
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• v.20 no.2
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• pp.11-17
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• 2011

The purpose of this study is 3 dimensional modeling of lower part of drilling system in offshore rig and simulation of drilling process. Recently, shipbuilding companies have been focusing on offshore rigs due to their high added-value and the reduced demand of new shipbuilding. In most cases, however, the basic design, installation and management of offshore rig are carried out by foreign companies. Therefore, it is difficult to obtain the knowledge and information of drilling system. In this study drilling devices, BOP(Blowout Preventor) and cementing job and mud circulation related components are included as the main components of offshore rig. The structure and function of them were analyzed from a viewpoint of object-oriented technique. On the basis of this analysis they were modeled in the 3 dimensional structure with 3D software tool such as CATIA and 3DVIA Composer. The drilling process was simulated according to the scenario of drilling operation. This simulation system can be effectively used for an educational tool for students and engineers in ocean plant industries.

• Ecology and Resilient Infrastructure
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• v.2 no.1
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• pp.64-79
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• 2015

We investigated the tidal current, hydrographic data, and benthic environment of major sea cucumber (Holothuroidea, de Blainville, 1834) habitats in Baengnyeongdo, Jindo and Uljin to understand the optimal environmental or ecological habitat for sea cucumbers. The three study areas were characterized by a cold-water mass of temperatures ranging $12{\sim}18^{\circ}C$, with an active circulation between the surface and deep waters. According to an analysis of the tidal current map, a strong flow velocity of $100{\sim}120cm\;s^{-1}$ appeared in Baengnyeongdo and Jindo. The three sea cucumber habitats showed the common characters of a bottom sediment composed of sand-silt, a diverse seaweed colony and benthic organisms, and boulders and rocks which provide a hideout for the organisms. We aimed to draw the optimal habitat condition for sea cucumbers in Korea, and the result showed that the low water temperature, rapid water flow, active vertical mixing between surface and deep waters, bottom composed by sand-silt, large rocks, and diverse seaweed colony and benthic organism were important factors. The optimal habitat for Juvenile sea cucumbers was the intertidal areas characterized by a muddy bottom, reef, and seaweed. The optimal habitat for adult sea cucumbers was characterized by a place where sand and mud are mixed, and the body size of the sea cucumber was proportional to water depth, and the relatively large boulders and rocks compared to the intertidal area.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.202-208
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• 2009

In order to understand the circulation of nutrient between muddy tidal flat and the surrounding coastal area, tidal time-scale variations in nutrient concentrations were seasonally investigated at the entrance of Hampyeong Bay. The results show that the temperature was higher in ebb tide and lower in flood tide during the summer, but it was lower in ebb tide and higher in flood tide during the autumn/winter. The salinity was higher in flood tide and lower in ebb tide during the summer/winter because of the inflow of external sea water resulting from the increase in the tide level. By contrast, the salinity was lower in flood tide and higher in ebb tide during the autumn. Salinity difference was lower than 0.3 psu between flood tide and ebb tide during survey period. Meanwhile, all nutrient concentrations observed in Hampyeong Bay was lower in flood tide and higher in ebb tide during the summer, and by contrast, it was higher in flood tide and lower in ebb tide during the winter. Characteristically, no clear variation of concentrations was found depending on the tide level during the autumn. This tidal variations imply that the muddy tidal flat of Hampyeong Bay supplies nutrients to the seawater in summer and removes nutrient from the seawater in winter. During tidal cycle, seasonal variation of nutrient concentration in seawater is considered as the result of complex interactions between the mud flat and external sea water.

• The Korean Journal of Quaternary Research
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• v.23 no.1
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• pp.25-37
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• 2009

Geochemical composition and clay minerals of surface and core sediments around off the Jeju Island were analyzed for identification of sediment origins. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. Smectite is highly concentrated (>8%) in the northwest near the South Yellow Sea and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe River. The relatively high abundance of kaolinite are found in northeastern nearshore area and the southwest near Changjiang estuary. It seems to be supplied from Changjiang River and the southwestern Korea rivers. The sediment accumulation rates measured by $^{210}Pb$ geochronrom mowere 0.20 to 0.54cm/mr or 0.15 to $0.42g/cm^2{\cdot}mr^{-1}$ AOJI, with decreasing rates from the west part to the east part, resulting in the supply of fine-grained suspended sediments from the Changjiang and Huanghe Rivers system. The discrimination diagrams clearly show that the sediments around Jeju Island in the northern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from Korean rivers and the Jeju Island.