VSP Modeling and Prestack Depth Migration

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2005 Vol.42, Issue 6 Preview Page Next Page

VSP Modeling and Prestack Depth Migration VSP 모델링 및 선 중합 깊이영역 구조보정: 장성형, 서상용, 고진석
Seonghyung Jang, Sangyong Suh and Jinseok Go

31 December 2005. pp. 625-633

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Abstract

For imaging the complex subsurface such as salt dome, faults, and folds, we perform prestack migration with surface seismic data or sometimes VSP (Vertical Seismic Profiling) data. The VSP data includes wavefield that can measure directly physical properites between surface and geological interfaces. The VSP is used for detecting dip, anisotropy, and reflection amplitude or waveform with respect to incidence angles. Here we applied forward modeling and prestack migration which are used for surface seismic data to VSP. We made synthetic VSP seismic data using the 8th order finite difference method for the acoustic wave equation and did VSP prestack migration. The synthetic VSP data to a simple three horizontally layered geological model showed the direct waves, reflection and refraction, which includes down-going and up-going waves with different direction. These were similar to the typical VSP data. Usually VSP prestack time migration needs filtering in order to separate up-going and down-going wave, but we did VSP prestack depth migration using inner product of back-propargated wavefield and the virtual source without filtering. The back-propagated wavefield was calculated from observed data and the virtual source was from the forward modeling using the observed data as a source term. The result of numerical modeling for the salt flank model shows that the upper horizontal and dipping layer were properly imaged. The better image of upper horizon and dipping layers than the lower layers indicates that seismic energy was concentrated on this part.

Keywords

VSP modeling

Partial derivative wavefield

Virtual source

Back-propagated wavefield

VSP prestack migration

암염돔, 단층, 습곡 등 복잡한 층서구조를 영상화하기 위해서는 지표면 탄성파 자료에 대해 선 중합 깊이영역 구조보정(prestack depth migration)이 필요하며 또한 탄성파 수직탐사(VSP)를 이용하기도 한다. 탄성파 수직탐사는 지표면과 지층경계면 사이에서 직접 물성을 측정할 수 있는 파동장을 기록하는 방법으로 지층경사, 이방성, 입사각에 따른 반사계수 변화, 파형변화 등 파악하는데 적용된다. 여기에서는 지표면 탄성파 자료에 적용되는 모델링과 구조보정법을 VSP자료에 적용하는 연구를 수행하였다. 인공합성 VSP 모델링에는 8차 근사 파동방정식의 유한차분법을 이용하였고, 지층구조 영상화는 가상음원과 역전파 파동장의 내적을 이용하여 실시하였다. 단순 수평 3층 모델에 대한 VSP 인공합성자료를 살펴 볼 때 직접파, 굴절파, 반사파 등이 모두 포함되어 있고 하향파, 상향파가 서로 반대 경사를 가지면서 나타나는 전형적인 VSP 자료 특성을 보여주고 있어 모델링방법이 적절하였음을 확인하였다. VSP 선 중합 깊이영역 구조보정은 상향파와 하향파를 분리하는 전 처리 과정없이 역전파 시킨 관측자료와 관측자료를 음원으로 이용하여 구한 가상음원과의 내적으로 영상을 구하였으며 암염돔 측면 모형실험 결과 상부 수평층과 경사층 영상화가 적절하게 이루어졌음을 알 수 있었다. 특히 상부 수평층과 경사층이 하부층에 비해 뚜렸하게 나타나는 것은 이 부분에 탄성파 에너지가 집중되었음을 보여준다.

키워드

VSP 모델링

편미분 파동장

가상음원

역전파 파동장

VSP 선 중합 구조보정

References

장성형, 신창수, 양승진, 고진석, 1997, “편미분파동장과 가상음원을 이용한 지하지질구조 영상화,” 한국지구시스템공학회지, Vol. 34, pp. 592-600.
Alford, R. M., Kelly, K. R., and Boor, D. M., 1974, “Accuracy of finite difference modeling of the acoustic wave equation,” Geophysics, Vol. 39, pp. 834-842.
Bevc, D., 1997, “Imaging complex structures with semirecursive Kirchhoff migration,” Geophysics, Vol. 62, pp. 577-588.
Cerjan, C., Kosloff, D., Kosloff, R., and Reshef, M., 1985, “A nonreflection boundary condition for discrete acoustic and elastic wave equation,” Geophysics, Vol. 50, pp. 705-708.
Claerbout, J. F., 1971, “Toward a unified theory of reflector mapping,” Geophysics, Vol. 36, pp. 467-481.
Graziella Kirtland Grech, M., Lawton, D. C., and Cheadle, S., 2003, “Integrated prestack depth migration of vertical seismic profile and surface seismic data from the Rocky Mountain Foothills of southern Alberta, Canada,” Geophysics, Vol. 68, pp. 1782-1791.
Hardage, B. A., 1983, Vertical Seismic Profiling, Vol. 14A, 14B, Geophysical Press.
Hinds, R. C., Anderson, N. L., and Kuzmiski, R., 1993, “An integrated surface seismic/seismic profile case study: Simonette area, Alberta,” Geophysics, Vol. 58, pp. 1676-1688.
Hokstad, K., Mittet, R., and Landr. M., 1998, “Elastic reverse time migration of marine walkaway vertical seismic profiling data,” Geophysics, pp. 1685-1695.
Jones, M., 1998, Cost effective VSP survey parameters, VSP Update, Schlumberger, no. 1.
Nichols, D. E., 1996, “Maximum energy travel times calculated in the seismic frequency band,” Geophysics, Vol. 61, pp. 253-263.
Kelly K. R., Ward, R. W., Treitel Sven, and Alford, R. M., 1974, “Synthetic seismograms: A finite difference approach,” Geophysics, Vol. 41, pp. 2-27.
Kreyszig, E., 1978, Introductory functional analysis with application, John Willy & Sons.
Loewenthal, D., Wang, C. J., Johnson, O. G., Juhlin, C., 1991, “High order finite difference modeling and reverse time migration,” Exploration Geophysics, Vol. 22, pp. 533-545.
Marfurt, K. J., 1978, Elastic wave equation migrationinversion, Ph. D dissertation, Columbia University Graduate School of Arts and Science.
Nichols, D. E, 1996, “Maximum energy traveltimes calculated in the seismic freguency band,” Geophysics, Vol. 61, pp. 253-263.
Raoult, J. J., Joncheray, B., and Carron, D., 1984, “The check VSP: A new vertical seismic data acquisition and processing technique,” SEG Expanded Abstract, pp. 839-402.
Ray, A., Brian, H., Van Gestel, J., 2004, “Largest 3D VSP in the deep water of the Gulf of Mexico to provide improved imaging in the Thunder Horse South field,” SEG Expanded Abstracts, pp. 422-425.
Shin, C., Jang, S., and Min, D., 2001, “Improved amplitude preservation for prestack depth migration by inverse scattering theory,” Geophysical Prospecting, Vol. 49, pp. 592-606.
Shin, C. S., and Sohn, H. J., 1998, “A frequency space 2-D scalar wave extrapolator using extended 25 points finite difference operators,” Geophysics, Vol. 63, pp. 289-296.
Tarantola, A., 1984, “Inversion of seismic reflection data in the acoustic approximation,” Geophysics, Vol. 49, pp. 1251-1266.
Van der Pal, R., Bacon, M., and Pronk, D., 1996, “3D walkaway VSP, enhancing seismic resolution for develo pment optimization of the Brent field,” First Break, Vol. 14, pp. 463-469.
Van Gestel, J., Hornby, B., and Ray, A., 2002, “VSP survey design using finite difference modeling,” SEG Expnaded Abstract, pp. 2361-2364.
Yilmaz, öEzdog̈oan, 1987, Seismic Data Processing, SEG.

Information

Publisher :The Korean Society of Mineral and Energy Resources Engineers
Publisher(Ko) :한국자원공학회
Journal Title :Journal of the Korean Society for Geosystem Engineering
Journal Title(Ko) :한국지구시스템공학회지
Volume : 42
No :6
Pages :625-633

[1] 장성형, 신창수, 양승진, 고진석, 1997, “편미분파동장과 가상음원을 이용한 지하지질구조 영상화,” 한국지구시스템공학회지, Vol. 34, pp. 592-600.

[2] Alford, R. M., Kelly, K. R., and Boor, D. M., 1974, “Accuracy of finite difference modeling of the acoustic wave equation,” Geophysics, Vol. 39, pp. 834-842.

[3] Bevc, D., 1997, “Imaging complex structures with semirecursive Kirchhoff migration,” Geophysics, Vol. 62, pp. 577-588.

[4] Cerjan, C., Kosloff, D., Kosloff, R., and Reshef, M., 1985, “A nonreflection boundary condition for discrete acoustic and elastic wave equation,” Geophysics, Vol. 50, pp. 705-708.

[5] Claerbout, J. F., 1971, “Toward a unified theory of reflector mapping,” Geophysics, Vol. 36, pp. 467-481.

[6] Graziella Kirtland Grech, M., Lawton, D. C., and Cheadle, S., 2003, “Integrated prestack depth migration of vertical seismic profile and surface seismic data from the Rocky Mountain Foothills of southern Alberta, Canada,” Geophysics, Vol. 68, pp. 1782-1791.

[7] Hardage, B. A., 1983, Vertical Seismic Profiling, Vol. 14A, 14B, Geophysical Press.

[8] Hinds, R. C., Anderson, N. L., and Kuzmiski, R., 1993, “An integrated surface seismic/seismic profile case study: Simonette area, Alberta,” Geophysics, Vol. 58, pp. 1676-1688.

[9] Hokstad, K., Mittet, R., and Landr. M., 1998, “Elastic reverse time migration of marine walkaway vertical seismic profiling data,” Geophysics, pp. 1685-1695.

[10] Jones, M., 1998, Cost effective VSP survey parameters, VSP Update, Schlumberger, no. 1.

[11] Nichols, D. E., 1996, “Maximum energy travel times calculated in the seismic frequency band,” Geophysics, Vol. 61, pp. 253-263.

[12] Kelly K. R., Ward, R. W., Treitel Sven, and Alford, R. M., 1974, “Synthetic seismograms: A finite difference approach,” Geophysics, Vol. 41, pp. 2-27.

[13] Kreyszig, E., 1978, Introductory functional analysis with application, John Willy & Sons.

[14] Loewenthal, D., Wang, C. J., Johnson, O. G., Juhlin, C., 1991, “High order finite difference modeling and reverse time migration,” Exploration Geophysics, Vol. 22, pp. 533-545.

[15] Marfurt, K. J., 1978, Elastic wave equation migrationinversion, Ph. D dissertation, Columbia University Graduate School of Arts and Science.

[16] Nichols, D. E, 1996, “Maximum energy traveltimes calculated in the seismic freguency band,” Geophysics, Vol. 61, pp. 253-263.

[17] Raoult, J. J., Joncheray, B., and Carron, D., 1984, “The check VSP: A new vertical seismic data acquisition and processing technique,” SEG Expanded Abstract, pp. 839-402.

[18] Ray, A., Brian, H., Van Gestel, J., 2004, “Largest 3D VSP in the deep water of the Gulf of Mexico to provide improved imaging in the Thunder Horse South field,” SEG Expanded Abstracts, pp. 422-425.

[19] Shin, C., Jang, S., and Min, D., 2001, “Improved amplitude preservation for prestack depth migration by inverse scattering theory,” Geophysical Prospecting, Vol. 49, pp. 592-606.

[20] Shin, C. S., and Sohn, H. J., 1998, “A frequency space 2-D scalar wave extrapolator using extended 25 points finite difference operators,” Geophysics, Vol. 63, pp. 289-296.

[21] Tarantola, A., 1984, “Inversion of seismic reflection data in the acoustic approximation,” Geophysics, Vol. 49, pp. 1251-1266.

[22] Van der Pal, R., Bacon, M., and Pronk, D., 1996, “3D walkaway VSP, enhancing seismic resolution for develo pment optimization of the Brent field,” First Break, Vol. 14, pp. 463-469.

[23] Van Gestel, J., Hornby, B., and Ray, A., 2002, “VSP survey design using finite difference modeling,” SEG Expnaded Abstract, pp. 2361-2364.

[24] Yilmaz, öEzdog̈oan, 1987, Seismic Data Processing, SEG.

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