• Tunnel and Underground Space
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• v.31 no.1
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• pp.41-51
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• 2021

The hydraulic fracturing developed to improve permeability of tight reservoir is one of key stimulation technologies for developing unconventional resources such as shale gas and deep geothermal energy. The experimental study was conducted to improve disadvantage of hydraulic fracturing which has simple fracture pattern and poor fracturing efficiency. The fracturing experiments was conducted for tight rock using various fracturing fluids, water, N2, and CO2 and the created fracture pattern and fracturing efficiency was analyzed depending on fracturing fluids. The borehole pressure increased rapidly and then made fractures for hydraulic fracturing with constant injection rate, however, gas fracturing shows slowly increased pressure and less fracture pressure. The 3D tomography technic was used to generate images of induced fracture using hydraulic and gas fracturing. The stimulated reservoir volume (SRV) was estimated increment of 5.71% (water), 12.72% (N2), and 43.82% (CO2) respectively compared to initial pore volume. In addition, permeability measurement was carried out before and after fracturing experiments and the enhanced permeability by gas fracturing showed higher than hydraulic fracturing. The fracture conductivity was measured by increasing confining stress to consider newly creating fracture and closing induced fracture right after fracturing. When the confining stress was increased from 2MPa to 10MPa, the initial permeability was decreased by 89% (N2) and 50% (CO2) respectively. This study shows that the gas fracturing makes more permeability enhancement and less reduction of induced fracture conductivity than hydraulic fracturing.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.57-72
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• 2000

The Murzuk Basin covers an area in excess of $350,000{\cal}km^2$, and is one of several intra-cratonic sag basins located on the Saharan Platform of North Africa. Compared with some of these basins, the Murzuk Basin has a relatively simple structure and stratigraphy, probably as a result of it's location on a the East Saharan Craton. The basin contains a sedimentary fill which reaches a thickness of about $4,000{\cal}m$ in the basin centre. This fill can be divided into a predominantly marine Paleozoic section, and a continental Mesozoic section. The principal hydrocarbon play consists of a glacial-marine sandstone reservoir of Cambro-Ordovician age, sourced and sealed by overlying Silurian shales. The present day borders of the basin are defined by tectonic uplifts, each of multi-phase generation, and the present day basin geometry bears little relation to the more extensive Early Palaeozoic sedimentary basin within which the reservoir and source rocks were deposited. The key to the understanding of the Cambro-Ordovician play is the relative timing of oil generation compared to the Cretaceous and Tertiary inversion tectonics which influenced source burial depth, reactivated faults and reorganised migration pathways. At the present day only a limited area of the basin centre remains within the oil generating window. Modelling of the timing and distribution of source rock maturity uses input data from AFTA and fluid inclusion studies to define palaeo temperatures, shale velocity work to estimate maximum burial depth and source rock geochemistry to define kinetics and pseudo-Ro. Migration pathways are investigated through structural analysis. The majority of the discovered fields and identified exploration prospects in the Murzuk Basin involve traps associated with high angle reverse faults. Extensional faulting occurred in the Cambro-Ordovician and this was followed by repeated compressional movements during Late Silurian, Late Carboniferous, Mid Cretaceous and Tertiary, each associated with regional uplift and erosion.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.11-19
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• 2020

In recent years, oil prices have continued to be low owing to the development of unconventional resources such as shale gas, coalbed methane gas, and tight gas. However, shipping companies are still experiencing difficulties because of recession in the shipping market. Hence, they devote considerable effort toward reducing operating costs. One of the important parameters for reducing operating costs is the frictional resistance of vessels. Generally, a vessel is covered with paint for smoothing its surface. However, frictional resistance increases with time owing to surface roughness, such as that caused by fouling. To prevent this, shipping companies periodically clean or repaint the surfaces of vessels using analyzed operating data. In addition, studies using various methods have been continuously carried out to identify this phenomenon such as fouling for managing ships more efficiently. In this study, numerical simulation was used to analyze the change in the resistance performance of a ship owing to an increase in surface roughness using commercial software, i.e., Star-CCM+, which solves the continuity and Navier eStokes equations for incompressible and viscous flow. The conditions for numerical simulation were verified through comparison with experiments, and these conditions were applied to three ships to evaluate resistance performance according to surface roughness.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.571-576
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• 2023

The initial development plans for the six reactor designs, soon after the release of Generation IV International Forum (GIF) TRM in 2002, were characterized by high ambition [1]. Specifically, the sodium-cooled fast reactor (SFR) and very-high temperature reactor (VHTR) gained significant attention and were expected to reach the validation stage by the 2020s, with commercial viability projected for the 2030s. However, these projections have been unrealized because of various factors. The development of reactor designs by the GIF was supposed to be influenced by events such as the 2008 global financial crisis, 2011 Fukushima accident [2, 3], discovery of extensive shale oil reserves in the United States, and overly ambitious technological targets. Consequently, the momentum for VHTR development reduced significantly. In this context, the aims of this study were to compare and analyze the development progress of the six Gen IV reactor designs over the past 20 years, based on the GIF roadmaps published in 2002 and 2014. The primary focus was to examine the prospects for the reactor designs in relation to spent nuclear fuel burning in conjunction with small modular reactor (SMR), including molten salt reactor (MSR), which is expected to have spent nuclear fuel management potential.

• Journal of Korea Port Economic Association
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• v.38 no.4
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• pp.87-106
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• 2022

Uncertainties in the energy market are increasing due to technology developments (shale revolution), trade wars, COVID-19, and the Russia-Ukraine war. Especially, since 2020, the risk of international trade in the energy market has increased significantly due to changes in the supply chain of transportation and due to prolonged demand reduction because of COVID-19 and the Russian-Ukraine war. Considering these points, this study analyzed connectedness between energy price, tanker index, and uncertainty to understand the connectedness between international trade in the energy market. Main results are summarized as follows. First, as a result of analyzing stable period and unstable period of the energy price model using the MS-VAR model, it was confirmed that both the crude oil market model and the natural gas market model had a higher probability of maintaining stable period than unstable period, increasing volatility by specific events. Second, looking at the results of the analysis of the connectedness between stable period and unstable period of the energy market, it was confirmed that in the case of total connectedness, connectedness between variables was increased in the unstable period compared to the stable period. In the case of the energy market stable period, considering the degree of connectedness, it was confirmed that the effect of the tanker freight index, which represents the demand-side factor, was significant. Third, unstable period of the natural gas market model increases rapidly compared to the crude oil market model, indicating that the volatility spillover effect of the natural gas market is greater when uncertainties affecting energy prices increase compared to the crude oil market.

• Journal of the Korean Society of Systems Engineering
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• v.11 no.1
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• pp.81-93
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• 2015

Steam Reforming H2 Generation (SRH2G) System is a chemical process to produce hydrogen through steam reforming of hydrocarbon. Largely speaking, there are two types of materials for the SRH2G: 1) Oil and coal, and 2)Natural Gas such as shale gas. From the perspective of cost, quality (purity), and environmental burden (pollution), the latter is much more desirable than the former. For this reason, research on SRH2G using natural gas is actively carried out, and implemented and operated in the various industry. In this paper, we develop a natural gas based SRH2G system via systems engineering approach. Specifically, we first derived stakeholder requirements, followed by systems requirements and finally system architecture via a tailored SE process for plant (called Plant Systems Engineering (PSE) process) based on ISO/IEC 15288. The developed method was applied to iron and steel plant as a case study. Through the case study, by the SE approach, we were convinced that a successful system satisfying stakeholders' requirements within the given constraints can be developed, verified and validated.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.245-260
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• 1991

Surficial dispersion patterns of heavy metals and toxic elements (U, Mo, Cu, Zn, Fe, Mn, Co, Cr, V, Ni, Pb, and Cd) were investigated in the Dukpyungri, Goesan area covered with low grade uranium-bearing black shales. Maximum abundance of U in the black shale was 455ppm. Radioactivity was counted at a maximum of 7cps in black shales, and was less than 0.5cps in shales, slates, and oil shales of the control areas. Enrichment of Mo, V, Cu, Zn, Cd, and Pb in black shales is particularly characteristic compared with shales, slates, and oil shales of the control areas, whereas contents of Mn, Cr, Co, and Th in all rock samples tend to be almost similar. Residual top soils (0~15cm depth) over black shales show high contents of Mo, Cu, Zn, Ni, Cd, and V in comparison with the control areas. Contents of trace elements in subsoils (15~30cm depth) were higher about one and half times than those in topsoils. Average contents of Mo, Cu, Pb, Zn, Cd and V in garden soil and playground soil of an elementary school in Dukpyungri, Goesan area, were high about two to fifteen times compared with the control areas. Contents of trace elements in stream sediments were higher from two to eight times than those in residual soils. Sodium, AI, K, V, Cr, and Fe were more enriched in the roots of pine than in the twigs of pine. Contents of Li, AI, V, Ni, Cd, Fe, and Co were higher in the roots of azalea than in the twigs of azalea. Enrichment of P, Ca, and Mg was remarkable in the twigs of both pine and azalea. Biological absorption coefficients for essential elements (Zn, P, Mn, Ca and K)tend to be high, whereas those for the non-essential elements.(Ba, Ti, V, and Mo) and toxic elements(Cr, Co, Pb and Ni) be low. Less mobile elements (Pd, Cd, and Co) tend to show anomalies with higher contrast than more mobile elements(Mo, V, Zn, Cu and Ni) in the area covered with black shales.

• Economic and Environmental Geology
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• v.49 no.3
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• pp.201-212
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• 2016

Due to growing problems securing stable mineral and energy resources with international political and economic changes, China has dedicated itself to strategies and policies to enhance its stable mineral and energy resources security. China has established a rare earth elements(REE) industry policy after the abolition of the REE exports quota system. China's six large REE companies have also been integrated into REE mining, smelting and refining companies. Efforts have been increased to enhance China's energy security through unconventional oil and gas exploration and development investment, as well as effort in R&D. The country will focus on technology development and exploration to promote commercial production of unconventional oil and gas based on countries with shale gas. China is making long-term contracts and joint ventures to ensure the acquisition of reliable mineral and energy resources from abroad. Government of China has proposed a range of initiatives, such as the integration of resources development strategies and environmental development strategies, internationalization of resource management, supply diversification and advancement, strengthening industry linking strategy, grouping and diversification strategy.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.587-603
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• 2018

3-D petroleum system modeling was performed on the Jeju Basin, offshore southern Korea to analyze the hydrocarbon migration and accumulation as well as the generation and expulsion of the hydrocarbon, based on subsurface structure maps of respective sedimentary formations. The lowermost formation deposited in Eocene time was assigned as a source rock, for which a mixed kerogen of type II and III was input in the modeling of oil and gas generation in consideration of the sedimentary environment of fluvio-lacustrine condition. Initial TOC was 4% as an input, based on the analysis of the well data and sedimentary environment. The modeling results show that a considerable amount of hydrocarbons was generated and expelled from the source rocks at the western Joint Development Zone (JDZ) sub-block 4, where the hydrocarbons was migrated to the above reservoir rocks at 20 Ma. The oil and gas in the reservoir rocks of the JDZ sub-block 4 are accumulated into the prospects with closure structures that has already been formed at the nearby areas. Another generation of hydrocarbon occurs from the source rock at the eastern border area of JDZ sub-block 1 and 2, where the expulsion of the hydrocarbons occurs at 10 Ma from the source rock into the above reservoir rocks, in which the accumulation also is expected. The generation, migration and accumulation were retarded at the eastern area of the JDZ sub-block 1 and 2, compared with the area of the western JDZ sub-block 4. Based on the modeling results, it is estimated that gases migrated laterally and vertically in long distance whereas oil migrated laterally in shorter distance than gases. A substantial amount of hydrocarbon could have seeped out of the reservoir formations to the surface since the migration of oil and gas actively occurred in Miocene time before the formation of seals. However, the modeling shows that the hydrocarbon could be accumulated smoothly into the closed structures that can be formed locally by alternation of sand and shale beds.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.44-52
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• 2002

Low temperature thermal desorption (LTTD) has become one of the cornerstone technologies used for the treatment of contaminated soils and sediments in the United States. LTTD technology was first used in the mid-1980s for soil treatment on sites managed under the Comprehensive Environmental Respones, Compensation and Liability Act (CERCLA) or Superfund. Implementation was facilitated by CERCLA regulations that require only that spplicable regulations shall be met thus avoiding the need for protracted and expensive permit applications for thermal treatment equipment. The initial equipment designs used typically came from technology transfer sources. Asphalt manufacturing plants were converted to direct-fired LTTD systems, and conventional calciners were adapted for use as indirect-fired LTTD systems. Other innovative designs included hot sand recycle technology (initially developed for synfuels production from tar sand and oil shale), recycle sweep gas, travelling belts and batch-charged vacuum chambers, among others. These systems were used to treat soil contaminated with total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), pesticides, polychlorinated biphenyls (PCBs) and dioxin with varying degrees of success. Ultimately, performance and cost considerations established the suite of systems that are used for LTTD soil treatment applications today. This paper briefly reviews the develpoment of LTTD systems and summarizes the design, performance and cost characteristics of the equipment in use today. Designs reviewed include continuous feed direct-fired and indirect-fired equipment, batch feed systems and in-situ equipment. Performance is compared in terms of before-and-after contaminant levels in the soil and permissible emissions levels in the stack gas vented to the atmosphere. The review of air emissions standards includes a review of regulations in the U.S. and the European Union (EU). Key cost centers for the mobilization and operation of LTTD equipment are identified and compared for the different types of LTTD systems in use today. A work chart is provided for the selection of the optmum LTTD system for site-specific applications. LTTD technology continues to be a cornerstone technology for soil treatment in the U.S. and elsewhere. Examples of leading-edge LTTD technologies developed in the U.S. that are now being delivered locally in global projects are described.