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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Geophysics and Geophysical Exploration
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Journal DOI :
Korean Society of Earth and Exploration Geophysicists
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Volume & Issues
Volume 18, Issue 4 - Nov 2015
Volume 18, Issue 3 - Aug 2015
Volume 18, Issue 2 - May 2015
Volume 18, Issue 1 - Feb 2015
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Leveling the Gamma-ray Spectrometric Data using Baseline Survey
Park, Yeong-Sue ; Rim, Hyoungrea ; Lim, Mutaek ; Shin, Young Hong ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 97~104
DOI : 10.7582/GGE.2015.18.3.097
KIGAM has surveyed most of the Korean territory since 1982 using airborne gamma-ray spectrometry, and complete the nationwide scale map in the near future. However, since the duration of survey is too long and the conditions of survey is not consistent, the data does not have physical consistency. In addition, the window counts (count/sec) were recorded instead of potassium, uranium and thorium radioelement concentrations. Thus, the data could not be registered to the International Atomic Energy Agency (IAEA) radioelement datum. This limits the usefulness of the data and it is not possible to easily combine surveys into regional compilations or make quantitative interpretations between different survey areas. To solve these problems, we undertook a test baseline survey over Jincheon-Eumseong area, to level the different two sets of data and to map radioelement concentrations. This survey confirms to IAEA radioelement baseline. The method and procedures of data leveling prepared by this study improve the usefulness and usability of the radiometric data, and make it enable to compile the nationwide scale radioelement concentration maps.
Resistivity Monitoring of Saturated Rock Cores at Room Temperature
Lee, Sang Kyu ; Lee, Tae Jong ; Yi, Myeong-Jong ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 105~114
DOI : 10.7582/GGE.2015.18.3.105
A long-term resistivity monitoring system has been developed for saturated cores in room temperature and humidity condition. A 3-channel water-pump continuously drops the water onto the top of saturated core sample surrounded by shrinkable tube as well as on the paper filters of the electrodes at both sides of the core sample, by which one can monitor the resistivity changes with maintaining full saturation of the rock core for a week or longer. Monitoring the resistivity changes has been performed with 3 kinds of rock samples including biotite gneiss, andesitic tuff, and shale for 9 days using the system. Consequently, it is proposed two hypothesis that conversion speed of temperature coefficient has close relation to the thermal properties of the rock sample and that the ratio of resistance between dry and saturated conditions for a rock sample can be related to the effective porosity of the sample. The ratio between dry and saturated resistance for the three rock types are 48, 705, and 2, while effective porosity was 3.7%, 3.3%, and 13.0%, respectively.
Modified Electrical Resistivity Survey for Leakage Detection of a Waterside Concrete Barrage
Lee, Bomi ; Oh, Seokhoon ; Im, Eunsang ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 115~124
DOI : 10.7582/GGE.2015.18.3.115
A modified electrical resistivity survey has been suggested and applied to a leakage detection problem of concrete barrage. We suggest the modified electrical resistivity methods using electrodes floating on the water and apply line current sources instead of conventional point current sources in order to facilitate simple analysis. In addition, the study introduced the following three variations of modified electrode array: Direct potential array, Parallel potential array and Cross potential array. These arrays were tested and investigated through numerical experiment, physical model experiment and geophysical field exploration in order to verify their applicability to the water leakage detection of a concrete barrage. When water leakage occurred, all kind of array operations demonstrated distinct changes of aspects of potential difference in graphs obtained by not only the numerical and physical model experiments but also geophysical field exploration. Therefore, this modified electrode arrays of electrical resistivity survey, which has been adapted to the concrete barrage, has been found to be a useful method to detect water leakage.
Suggestion of the Modified Archie's Formula for Calculating Water Saturation of Clean Sandstone and Carbonate Rocks
Lee, Sang-Hee ; Ko, Eun-Ji ; Kim, Jin-Hoo ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 125~132
DOI : 10.7582/GGE.2015.18.3.125
The water saturation (
), which is very important to estimate hydrocarbon reserves in the reservoir, has been determined from resistivity index (RI) by using the Archie's formula. However, in many cases, it has been reported that n is not constant for a given formation and it could be varied with water saturation. In addition, it frequently happens that the line obtained by linear regression analysis on log-log scale does not pass through the origin. In order to overcome these drawbacks, we suggested a modified Archie's formula, which can handle almost all the RI vs.
cross-plots whether the trend is straight or curved and whether it passes through the origin or not. We also demonstrated that how to determine conductivity exponent
, critical water saturation
, and saturation distribution factor b in the laboratory to use the modified Archie's formula. Since the modified Archie's formula takes into account pore structure, pore water distribution, and wettability of reservoir such as clean sandstone and carbonate rocks, it might improve field applicability.
Effects of Earth's Atmosphere on Terrestrial Reference Frame : A Review
Na, Sung-Ho ; Cho, Jungho ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 133~142
DOI : 10.7582/GGE.2015.18.3.133
Displacement of the Earth's surface due to atmospheric loading has been recognized since a century years ago, and its accurate estimation is required in present day geodesy and surveying, particularly in space geodesy. Atmospheric load deformation in continental region can readily be calculated with the given atmospheric pressure field and the load Green's function, and, in near coastal area, approximate model is used for the calculation. The changes in the Earth's atmospheric circulation and the seasonal variation of atmospheric pressure on two hemispheres of the Earth are the each main causes of variation of the Earth's spin angular velocity and polar motion respectively. Wind and atmospheric pressure do the major role in other periodic and non-periodic perturbations of the positions in the Earth's reference frame and variations in the Earth's spin rotational state. In this reviewing study, the developments of related theories and models are summarized along with brief description of phenomena, and the geodetic perturbing effects of a hypothetical typhoon passing Korea are shown as an example. Finally related existing problems and further necessary studies are discussed in general.
An Analysis on Applicability of Geophysical Exploration Methods to Monitoring Polymer-flooding
Cheon, Seiwook ; Park, Chanho ; Ku, Bonjin ; Nam, Myung Jin ; Son, Jeong-Sul ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 143~153
DOI : 10.7582/GGE.2015.18.3.143
Polymer flooding for enhancing hydrocarbon production injects into a reservoir polymer solution that is viscous. It is very important to monitor the behavior pattern of the polymer solution in order to evaluate the effectiveness of polymer flooding. To monitor the distribution of polymer solution and thus fluid substitution within the reservoir, we first construct seismic and resistivity rock physics models (RPMs), which are functions of reservoir parameters such as rocks and type of fluid, fluid saturation. For the seismic and resistivity RPMs, responses of seismic and electromagnetic (EM) tomography are numerically simulated as polymer injection, using two dimensional (2D) staggered-grid finite difference elastic modeling and 2.5D finite element EM modeling algorithms, respectively. In constructing RPM for EM tomography, three different reservoir rocks are considered: clean-sand, dispersed shale-sand, and sand-shale lamination rocks. The polymer solution is assumed to have 2 wt% of polymer as normally generated, while water is freshwater or saltwater. Further, neutron logging is also considered to check its sensitivity to polymer flooding. The techniques discussed in the paper are important in monitoring not only hydrocarbon but also geothermal reservoirs.
Neutron Induced Capture Gamma Spectroscopy Sonde Design and Response Analysis Based on Monte Carlo Simulation
Won, Byeongho ; Hwang, Seho ; Shin, Jehyun ; Kim, Jongman ; Kim, Ki-Seog ; Park, Chang Je ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 154~161
DOI : 10.7582/GGE.2015.18.3.154
For efficiently designing neutron induced gamma spectroscopy sonde, Monte Carlo simulation is employed to understand a dominant location of thermal neutron and classify the formation elements from the energy peak of capture gamma spectrum. A pulsed neutron generator emitting 14 MeV neutron particles was used as a source, and flux of thermal neutron was calculated from the twelve detectors arranged at each 10 cm intervals from the source. Design for reducing borehole effects using shielding materials was also applied to numerical sonde model. Moreover, principal elements and quantities of numerical earth models were verified through the energy spectrum analysis of capture gamma detected from a gamma detector. These results can help to enhance the signal-to-noise ratio, and determine an optimal placement of capture gamma detectors of neutron induced gamma spectroscopy sonde.
Comparison of Spatial Autocorrelation (SPAC) Analyses: Temporal Averaging and Spatial Averaging
Park, Jechan ; Kang, Tae-Seob ;
Geophysics and Geophysical Exploration, volume 18, issue 3, 2015, Pages 162~166
DOI : 10.7582/GGE.2015.18.3.162