• Journal of agriculture & life science
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• v.53 no.6
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• pp.35-44
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• 2019

The objectives of this study were to identify engineering problems in the design and installation of cable logging operation that affects productivity through case study of actual logging sites, and to analyze associated productivity loss and increased cost. As a result of the study, when the geographic conditions and engineering safety of the site are not sufficiently considered, deflection of the cable line can not be secured. Hourly productivity of the operation decreased to 65% and the logging cost increased by more than two times compared to the productive yarding operation, which lowered overall efficiency of the operation. Thus, it is required to spread filed technologies that minimize unnecessary production cost incurred due to the in-efficient logging operations as well as secure work safety and efficiency to expand cable logging operation throughout the country.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.369-376
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• 2007

Electrical resistivity tomography was carried out at seawater intrusion monitoring wells located at watershed in coastal areas. It is difficult to identify the characteristics of resistivity near monitoring well in case of using high signalto-noise ratio array due to the high conductivity condition in coastal aquifer although electrical resistivity survey is well adopted to delineate hydrogeological characteristics with the distribution of electrical resistivity. To improve the quality of electrical resistivity survey for two sites with seawater intrusion monitoring wells, inversion with the results of holeto-surface electrical resistivity tomography using single well was executed. The results of inversion for aquifer near wells were verified with the results of drilling log with the informations of fracture, electrical conductivity logging and normal resistivity logging. The inversion for aquifer near one of two wells was also performed at low and high tide with the same electrodes, respectively. From the inversion result, it is possible to obtain the resistivity images with high resolution and to identify the characteristics of aquifer related to seawater intrusion with tidal fluctuation. From this study, it was demonstrated that the hole-to-surface electrical resistivity tomography method accompanied with drilling log, electrical conductivity logging and normal resistivity logging would be useful to delineate the hydrogeological structures near monitoring wells in coastal areas.

• Geophysics and Geophysical Exploration
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• v.22 no.1
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• pp.1-11
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• 2019

Well logging technologies are used to measure the physical properties of reservoirs through boreholes. These technologies have been utilized to understand reservoir characteristics, such as porosity, fluid saturation, etc., using equations based on rock physics models. The analysis of well logs is performed by selecting a reliable rock physics model adequate for reservoir conditions or characteristics, comparing the results using the Archie's equation or simandoux method, and determining the most feasible reservoir properties. In this study, we developed a joint inversion algorithm to estimate physical properties in shaly sandstone reservoirs based on the pre-existing algorithm for sandstone reservoirs. For this purpose, we proposed a rock physics model with respect to shale volume, constructed the Jacobian matrix, and performed the sensitivity analysis for understanding the relationship between well-logging data and rock properties. The joint inversion algorithm was implemented by adopting the least-squares method using probabilistic approach. The developed algorithm was applied to the well-logging data obtained from the Colony gas sandstone reservoir. The results were compared with the simandox method and the joint inversion algorithms of sand stone reservoirs.

• 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.

• 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.

• 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.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.87-98
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• 1998

Multiple logging techniques consisting of geophysical logs, care logs, physical property measurements on core samples have been adopted on a test borehole drilled in the Pungam basin ; a small Cretaceous sedimentary basin located in Sosok area, Hongchon-gun, Kangwon Province, Korea. This study has been made to solve the problem of mismatches between the results of geophysical log and core log analyses. And the cause and range of depth errors as well as logging responses were studied. The result shows that the depth error caused by geophysical log is so small that it can be used as a reliable depth criterion in the borehole. The analysis of physical property measurements is also shown as very effective in determining the real depth and the geology of the borehole.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.50-57
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• 2006

Development of structures such as slope and tunnel, waste disposal, oil and LPG storages, and underground power house and so on, is increasing with the year. The method for appropriate estimation of rock state such as fresh or damaged rocks is also requested with increasing structural development. On these purposes, seismic logging system, which is a simple and easy way for handling as well as small and light, has been developed. Seismic logging method is one of logging tests, which is able to evaluate the state of rock mass with various shapes and is possible to obtain the relatively accuracy data at situ state. In addition, seismic logging method is at to apply to estimate structural behavior, before and after support installed. According to the results obtained from this study, firstly, it is clear that the extent of damage in rock slope due to blasting is able to be evaluated with quantity using seismic logging method, moreover to decide the damage zone in rock slope reasonably. Secondly, it is expected that installing depth of support is able to be decided more effectively and economically, using the results of seismic logging data. Finally, seismic logging method is also able to be applied safety supervision of structures, before and after support installed.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.231-236
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• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.155-162
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• 2014

We performed MCNP modeling for density log, and examined its reliability and validity comparing the correction curves from physical borehole model. Based on the constructed numerical model, numerical modelings of density sonde in three-inch borehole were carried out under the various conditions such as the existence and type of casing or fluid, and also the stand-off between the sonde and borehole wall. These results of numerical modeling quantitatively reflect effects of casing and fluid in borehole, and moreover, demonstrate constant patterns with interval change from borehole wall. From this study, numerical modeling using MCNP shows a good applicability for well logging, and therefore, can be efficiently used for the calibration of well logging data under the various borehole conditions.