• Geophysics and Geophysical Exploration
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• v.12 no.4
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• pp.309-315
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• 2009

Integrated interpretation of multi-geophysical data has been continuously used in terms that it has provided more confident information than the result from single-geophysical data. Especially, geostatistical integration has its own superiority that it is possible to deal with spatial characteristics as well as physical properties of survey data and the process of integration is clear. This paper further extends the previous work of geostatistical inversion for integrated interpretation. In this paper, we propose a new way of dealing with the case that the multi-geophysical data do not share the measurement range. According to the geostatistical kriging, the closer between the measurement points, the smaller kriging variance we get, and vice versa. We used this spatial properties as a weighting value to the process of geostatistical inversion for the geophysical data integration. An objective way to integrate different kinds of geophysical data measured at different ranges is provided with this algorithm.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.314-321
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• 2007

Recently, multi-dimensional joint inversion of geophysical data based on fundamentally different physical properties is being actively studied. Joint inversion can provide a way to obtaining much more accurate image of the subsurface structure. Through the joint inversion, furthermore, it is possible to directly estimate non-geophysical material properties from geophysical measurements. In this study, we developed a new algorithm for jointly inverting dc resistivity and seismic traveltime data based on the multiple constraints: (1) structural similarity based on cross-gradient, (2) correlation between two different material properties, and (3) a priori information on the material property distribution. Through the numerical experiments of surface dc resistivity and seismic refraction surveys, the performance of the proposed algorithm was demonstrated and the effects of different regularizations were analyzed. In particular, we showed that the hidden layer problem in the seismic refraction method due to an inter-bedded low velocity layer can be solved by the joint inversion when appropriate constraints are applied.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.65-69
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• 2004

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1994.07a
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• pp.75-91
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• 1994

제주도의 지하수는 상위지하수, 기저지하수, 연안용출수, 심부지하수 등으로 분류될 수 있다. 이들을 효율적으로 활용하고 또 보존, 관리하기 위하여는 탐사가 선행되어야 한다. 구성물질의 물성대비를 탐사의 원리로 하는 물리탐사는 간접적 정보를 제공한다는 점에서 조사단계에서 흔히 간과되어 왔으나, 지표 상부에서 지하 심부까지의 정보를 제공할 수 있는 유일한 탐사방법이라는 점에서 그 중요성이 재인식되어야 한다. 물리탐사는 비파괴적인 탐사방법일 뿐 아니라 날은 탐사범위를 상대적으로 짧은 기간에 탐사할 수 있는 경제성을 갖고 있기 때문에 결과적으로 조사단계에서 소요되는 총비용을 현저히 줄일 수 있기 때문이다. 필자는 여기서, 제주도의 지하수문제에 대하여 물리탐사가 담당할 수 있는 역할에 대하여 최근의 탐사실례들을 통하여 기술하고자 한다. 이들 중에는 '복합 물리탐사방법에 의한 지하수탐사', '항공원격탐사에 의한 해안 용출수탐사', '물리탐사에 의한 해수침입영역 조사' 그리고 지하수 부존과 밀접한 관련이 있는 '지질구조선 탐사' 등이 포함되어 있다. 후속의 지질조사와 시추조사에서 얻은 직접적 정보들이 물리탐사에 의한 해석에 feedback 될 수 있는 조사체계를 갖춘다면 향후 제주도의 지하수와 관련한 문제에 물리탐사가 보다 효과적으로 사용될 수 있을 것임을 강조한다.

• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.54-63
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• 2015

Petrophysical parameters such as porosity and fluid saturation which provide useful information for reservoir characterization could be estimated by rock physics model (RPM) using seismic velocity and resistivity. Therefore, accurate P-wave velocity and resistivity information have to be obtained for successful estimation of the petrophysical parameters. Compared with the individual inversion of electromagnetic (EM) or seismic data, the joint inversion using both EM and seismic data together can reduce the uncertainty and gives the opportunity to use the advantages of each data. Thus, more reliable petrophysical properties could be estimated through the joint inversion. In this paper, for the successful estimation of petrophysical parameters, we proposed an effective method which applies a grid-search method to find the porosity and fluid saturation. The relations of porosity and fluid saturation with P-wave velocity and resistivity were expressed by using RPM and the improved resistivity distribution used to this study was obtained by joint inversion of seismic and EM data. When the proposed method was applied to the synthetic data which were simulated for subsea reservoir exploration, reliable petrophysical parameters were obtained. The results indicate that the proposed method can be applied for detecting a reservoir and calculating the accurate oil and gas reserves.

• Geophysics and Geophysical Exploration
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• v.17 no.4
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• pp.187-201
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• 2014

Compared with the separated inversion of electromagnetic (EM) and seismic data, a joint inversion using both EM and seismic data reduces the uncertainty and gives the opportunity to use the advantage of each data. Seismic fullwaveform inversion allows velocity information with high resolution in complicated subsurface. However, it is an indirect survey which finds the structure containing oil and gas. On the other hand, marine controlled-source EM (mCSEM) inversion can directly indicate the oil and gas using different EM properties of hydrocarbon with marine sediments and cap rocks whereas it has poor resolution than seismic method. In this paper, we have developed a joint EM inversion algorithm using a cross-gradient technique. P-wave velocity structure obtained by full-waveform inversion using plane wave encoding is used as structure constraints to calculate the cross-gradient term in the joint inversion. When the jointinversion algorithm is applied to the synthetic data which are simulated for subsea reservoir exploration, images have been significantly improved over those obtained from separate EM inversion. The results indicate that the developed joint inversion scheme can be applied for detecting reservoir and calculating the accurate oil and gas reserves.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.177-189
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• 2012

Evaluation of three-dimensional ore body modeling has been performed by applying the geostatistical integration technique to multiple geophysical (electrical resistivity, MT) and geological (borehole data, physical properties of core) information. It was available to analyze the resistivity range in borehole and other area through multiple geophysical data. A correlation between resistivity and density from physical properties test of core was also analyzed. In the case study results, the resistivity value of ore body is decreased contrast to increase of the density, which seems to be related to a reason that the ore body (magnetite) includes heavy conductive component (Fe) in itself. Based on the lab test of physical properties in iron mine region, various geophysical, geological and borehole data were used to provide ore body modeling, that is electrical resistivity, MT, physical properties data, borehole data and grade data obtained from borehole data. Of the various geostatistical techniques for the integrated data analysis, in this study, the SGS (sequential Gaussian simulation) method was applied to describe the varying non-homogeneity depending on region through the realization that maintains the mean and variance. With the geostatistical simulation results of geophysical, geological and grade data, the location of residual ore body and ore body which is previously reported was confirmed. In addition, another highly probable region of iron ore bodies was estimated deeper depth in study area through integrated modeling.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.15-25
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• 2018

Seismic inversion is a high-resolution tool to delineate the subsurface structures which may contain oil or gas. On the other hand, marine controlled-source electromagnetic (mCSEM) inversion can be a direct tool to indicate hydrocarbon. Thus, the joint inversion using both EM and seismic data together not only reduces the uncertainties but also takes advantage of both data simultaneously. In this paper, we have developed a simultaneous joint inversion approach for the direct estimation of reservoir petrophysical parameters, by linking electromagnetic and seismic data through rock physics model. A cross-gradient constraint is used to enhance the resolution of the inversion image and the maximum likelihood principle is applied to the relative weighting factor which controls the balance between two disparate data. By applying the developed algorithm to the synthetic model simulating the simplified gas field, we could confirm that the high-resolution images of petrophysical parameters can be obtained. However, from the other test using the synthetic model simulating an anticline reservoir, we noticed that the joint inversion produced different images depending on the model constraint used. Therefore, we modified the algorithm which has different model weighting matrix depending on the type of model parameters. Smoothness constraint and Marquardt-Levenberg constraint were applied to the water-saturation and porosity, respectively. When the improved algorithm is applied to the anticline model again, reliable porosity and water-saturation of reservoir were obtained. The inversion results indicate that the developed joint inversion algorithm can be contributed to the calculation of the accurate oil and gas reserves directly.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.185-189
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• 2009

Integrated analysis of GPR, impact echo and impulse response for detection of the rear cavity of concrete was performed on the test-bed which was made in the same scale and component ratio to the real concrete structure. GPR survey may roughly delineate the location of the cavity, but applying the IE and IR technique to the test-bed, the location was clearly identified.

• 한국지구물리탐사학회:학술대회논문집
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• 2011.10a
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• pp.149-150
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• 2011