• Title/Summary/Keyword: 지구물리 검층

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석회암지역에서 불연속면의 물리검층반응

  • Kim, Yeong-Hwa;Yang, Yeong-Geun;Kim, Jung-Yeol;Kim, Yu-Seong
    • Journal of the Korean Geophysical Society
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    • v.4 no.2
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    • pp.95-102
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    • 2001
  • As a basic study of characterizing fracture condition in bore hole, conventional geophysical well log data consisting of sonic, gamma-gamma and resistivity logs were compared with geological core log and acousic televiewer log in limestone geology. Discontinuities shown on the acoustic televiewer log and the core log show fairly good correlation. The conventional Geophysical log is also shown to bi effective in locating discontinities in limestone geology; sonic log shows the best result and resistivity shows the worst. Particularly, the combination method of density and sonic logs is shown to be the most effective in delineating discontinuities.

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Geophysical Well Logs in Basaltic Volcanic Area, Jeju Island (제주 현무암 지역에서 물리검층 자료 해석)

  • Hwang, Se-Ho;Shin, Je-Hyun;Park, Ki-Hwa;Park, In-Hwa;Koh, Gi-Won
    • Geophysics and Geophysical Exploration
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    • v.9 no.3
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    • pp.231-240
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    • 2006
  • A variety of geophysical well loggings have been conducted to investigate the geological characteristics for basaltic volcanic area in Jeju Island. Specially, there is no precedent case study using geophysical well loggings in Jeju Island. And so, the proper understandings for geological features of Jeju Island are the key to interpret geophysical well logs. Presently, seawater intrusion monitoring systems have been constructed for systematic development and conservation of groundwater resources. As the results of geophysical well loggings in this seawater intrusion monitoring boreholes, the responses of well logs for saturated zone have distinctly identified basalt sequences. In particular, neutron logging, gamma-gamma (density) logging, and resistivity logging have well exhibited the characteristics of lava flows and lithologic boundaries. In hyalocastite, porosity is high, and resistivity is low. Eventually, geophysical well logs are useful for securing sustainable development of groundwater in Jeju Island in that it has identified the characteristics of geological responses.

Application of geophysical well logging to fracture identification and determination of in-situ dynamic elastic constants. (물리검층에 의한 파쇄대 인식과 동적 지반정수의 산출)

  • Hwang, Se-Ho;Lee, Sang-Kyu
    • 한국지구물리탐사학회:학술대회논문집
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    • 1999.08a
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    • pp.156-175
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    • 1999
  • Recently the application of geophysical well logging to geotechnical site investigation is increasing, because the merit that geophysical logs provide the high resolution and in-situ physical properties in volumes of rock surrounding the borehole. Geophysical well logs are used to identify lithologic boundaries and fracture, to determine the physical properties of rock(i.e., density, velocity etc.), and to detect permeable fracture zones that could be conduits for ground water movement through the rocks. The principle of heat-pulse meter, the calibration of gamma-gamma logging, and principles and data processing of full waveform sonic logging are briefly reviewed, and the case studies of geophysical logs are discussed. Correlation between velocity by sonic logging and rock mass classification such as RMR(Rock Mass Rating) value is considered.

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Comparison of Physical Properties obtained from Geophysical Well Log and Core Property Measurements in Gabsan Formation (갑산층 석회암지역에서의 코어물성과 검층물성 비교)

  • 김영화;김기주
    • The Journal of Engineering Geology
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    • v.9 no.3
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    • pp.253-265
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    • 1999
  • Physical properties of Paleozoic sedimentary rocks in Gabsan formation in Jechon area were obtained by both geophysical well log methods and core property measurements, and the similarity and difference shown between the well log and core log responses were analyzed. The physical properties obtained are natural gamma, resistivity and density. From the difference in density response between the well log and core measurement, the need of correction for natural gamma effect on density log was strongly suggested. And fairly good correlation was obtained between well log and core properties, and among natural gamma, resistivity and density by applying natural gamma correction on density log. It is noted that shale in Gabsan formation reveals very high density, even higher than the density of adjacent non-porous limestone.

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Applicability of Geophyscal Well Logging in the Assessment of Seawater Intrusion (임해지역 해수침투 평가를 위한 물리검층의 적용성)

  • Lee Sang-Gyu;Hwang Sae-Ho;Hwang Hak-Su;Park In-Hwa
    • Geophysics and Geophysical Exploration
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    • v.3 no.3
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    • pp.101-111
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    • 2000
  • In order to assess the seawater intrusion, induction, temperature and conductivity of fluid, and natural gamma logs were obtained in nine wells at the three study areas having different hydrogeologic characteristics. Besides surface geophysical exploration, supplementary geophysical well logs were carried out to understand the hydrogeological characteristics related to the seawater intrusion in the study areas. The geophysical well logs have been proved to increase the accuracy of interpretation of the surface geophyscial exploration's data for assessment of seawater intrusion, and to get the optimum depth for a long monitoring of groundwater. They, also, revealed that the identification of hydrogeological units for strata's porosity was able to be achieved and were illustrated the applicability of geophysical well logs monitoring. Finally, geophysical well logs are expected to play to get the more quantitative information of seawater infusion, if it is fully collaborated with a better method that is strata's resistivity determination with not relatively much effected by seawater within the drilled borehole and that is the porosity measurement with built on small diameter PVC casing.

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A Review on nuclear magnetic resonance logging: fundamental theory and measurements (자기공명검층: 기본 이론 및 자료 측정)

  • Jang, Jae Hwa;Nam, Myung Jin
    • Geophysics and Geophysical Exploration
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    • v.15 no.4
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    • pp.235-244
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    • 2012
  • Nuclear magnetic resonance (NMR) logging has been considered one of the most complicated nevertheless, one of the most powerful logging methods for the characterization on of both rocks and natural fluids in formation. NMR measures magnetized signals (polarization and relaxation) between the properties of hydrogen nucleus called magnetic moment and applied magnetic fields. The measured data set contains two important petrophysical properties such as density of hydrogen in the fluids inside the pore space and the distinct decay rate for fluid type. Therefore, after the proper data processing, key petrophysical information, not only the quantities and properties of fluids but also supplies of rock characterization in a porous medium, could be archived. Thus, based on this information, several ongoing researches are being developed in estimating aspects of reservoir productivity information, permeability and wettability since it is the key to having correct interpretation. This study goes through the basic theory of NMR at first, and then reviews NMR logging tools as well as their technical characteristics. This paper also briefly discusses the basic knowledge of NMR simulation algorithm by using Random walk.

A study on slim-hole neutron logging based on numerical simulation (소구경 시추공에서의 중성자검층 수치모델링 연구)

  • Ku, Bonjin;Nam, Myung Jin
    • Geophysics and Geophysical Exploration
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    • v.15 no.4
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    • pp.219-226
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    • 2012
  • This study provides an analysis on results of neutron logging for various borehole environments through numerical simulation based on a Monte Carlo N-Particle (MCNP) code developed and maintained by Los Alamos National Laboratory. MCNP is suitable for the simulation of neutron logging since the algorithm can simulate transport of nuclear particles in three-dimensional geometry. Rather than simulating a specific tool of a particular service company between many commercial neutron tools, we have constructed a generic thermal neutron tool characterizing commercial tools. This study makes calibration chart of the neutron logging tool for materials (e.g., limestone, sandstone and dolomite) with various porosities. Further, we provides correction charts for the generic neutron logging tool to analyze responses of the tool under various borehole conditions by considering brine-filled borehole fluid and void water, and presence of borehole fluid.