Automatic Velocity Analysis Considering Anisotropy

doi:10.12972/ksmer.2013.50.1.011

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2013 Vol.50, Issue 1 Preview Page Next Page

Research Paper

Automatic Velocity Analysis Considering Anisotropy 이방성을 고려한 자동속도분석: 권택현·변중무·설순지
Taekhyun Kwon, Joongmoo Byun and Soon Jee Seol

28 February 2013. pp. 11-20

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Abstract

Data acquisition including long spread offsets is recently implemented due to the development of exploration techniques. If NMO correction was carried out through the conventional NMO velocity analysis to data acquired at Vertical Transversely Isotropic (VTI) media, the shape of the moveout called “hockey-stick” could frequently appear in the part of long spread offset. This indicates that the conventional NMO velocity analysis dose not provide correct results. Thus, in this study, an NMO velocity analysis module was developed not only considering anisotropy but also extracting an anisotropic parameter η. In addition, the developed modulecan process huge amount of data like 3D data efficiently and rapidly because it picks the maximum energy points on the semblances automatically. It is important to obtain high-resolution semblances in order to pick the maximum points accurately. Therefore, the developed module uses a bootstrapped differential semblance (BDS) instead of a conventional semblance to provide better resolution. To validate our developed module, it was applied to thenumerical and the physical modeling data sets. The extracted velocities and anisotropic parameters were reasonable except in the case of deeply tilted layers, and stacked results were also improved.

Keywords

Anisotropy

Velocity analysis

Anisotropic parameter

Automatic

VTI media

최근에는 탄성파 반사법 탐사기술의 발달로 먼 거리 벌림(offset)을 이용한 자료취득이 많이 이루어지고 있다. 이때 횡적 등방성(VTI) 매질에서 획득한 자료에 일반적인 NMO 속도분석을 적용하여 NMO 보정을 수행할 경우 먼 거리 벌림에서 탄성파 이벤트들이 위로 말려 올라가는 현상이 나타나며 이는 정확한 속도분석이 이루어지지 않았음을 나타낸다. 이 연구에서는 이방성을 고려한 NMO 속도분석을 수행함과 동시에 이방성을 나타내는 이방성 변수 를 추출하는 모듈을 개발하였다. 또한 자동으로 닮음(semblance) 상에서 최대 에너지 지점을 선발하여 속도분석을 수행할 수 있도록 하여 3차원 탐사 자료와 같이 방대한 양의 자료의 경우에도 효율적이고 빠르게 자료처리를 할 수 있도록 하였다. 이러한 자동선발을 이용한 속도분석에 있어서 닮음의 해상도는 매우 중요한 요소이므로 보다 높은 해상도의 닮음을 제공하는 BDS(Bootstrapped Differential Semblance)를 이용하였다. 그리고 이 연구에서 개발한 모듈을 검증하기 위해 합성탄성파 탐사자료 및 축소모형 실험 자료에 적용하였고 그 결과 NMO 속도분석의 가정에 부합하는 경사가 크지 않은 지층의 경우 실제 모델과 거의 유사한 속도와 이방성 변수 값들을 추출하였고 중합결과 또한 향상됨을 확인하였다.

키워드

이방성

속도분석

이방성 변수

자동

횡적 등방성 매질

References

Abbad, B., Ursin, B. and D. Rappin., 2009, “Automatic nonhyperbolic velocity analysis,” Geophysics, 74(2), U1-U12.
Alkhalifah, T. and Tsvankin, I., 1995, “Velocity analysis for transversely isotropic media,” Geophysics, 60, pp. 1550-1566.
Alkhalifah, T., 1997, “Velocity analysis using nonhyperbolic moveout in transversely isotropic media,” Geophysics, v. 62, pp. 1839-1854.
Choi, H., Byun, J. and Seol, S.J., 2010, “Automatic velocity analysis using bootstrapped differential semblance and global search methods,” Exploration Geophysics, 41, pp. 31-39.
Choi, H., Byun, J., Seol, S.J., Ko, S., Kwak, J.Y. and Cha, Y., 2009, “Application of Automatic Velocity Analysis Using Monte Carlo Method,” Journal of Korean Society for Geosystem Engineering, Vol. 46, No. 5, pp. 571-581.
Douma, H. and M. van der Baan., 2008, “Rational interpolation of qP-traveltimes for semblance-based anisotropy estimation in layered VTI media.” Geophysics 73(4): D53-D62.
Fomel, S. and Stovas, A., 2010, “Generalized nonhyperbolic moveout approximation,” Geophysics 75(2): U9-U18.
Grechka, V. and Tsvankin, I., 1998, “Feasibility of nonhyperbolic moveout inversion in transversely isotropic media,” Geophysics, 63(3), pp. 957-969.
Thomsen, L., 1986, “Weak elastic anisotropy,” Geophysics, 51, pp. 1954-1966.
Thomsen, L., 2002, Understanding seismic anisotropy in exploration and exploitation, Distinguished Instructor Series No.5, SEG, USA, p. 32.
Tsvankin, I. and Thomsen, L., 1994, “Nonhyperbolic reflection moveout in anisotropic media,” Geophysics, 59, pp. 1290-1304.
Wang, X. and Tsvankin, I., 2009, “Estimation of interval anisotropy parameters using velocity-independent layer stripping,” Geophysics, 74, pp. WB117-WB127.

Information

Publisher :The Korean Society of Mineral and Energy Resources Engineers
Publisher(Ko) :한국자원공학회
Journal Title :Journal of the Korean Society of Mineral and Energy Resources Engineers
Journal Title(Ko) :한국자원공학회지
Volume : 50
No :1
Pages :11-20
DOI :https://doi.org/10.12972/ksmer.2013.50.1.011

[1] Abbad, B., Ursin, B. and D. Rappin., 2009, “Automatic nonhyperbolic velocity analysis,” Geophysics, 74(2), U1-U12.

[2] Alkhalifah, T. and Tsvankin, I., 1995, “Velocity analysis for transversely isotropic media,” Geophysics, 60, pp. 1550-1566.

[3] Alkhalifah, T., 1997, “Velocity analysis using nonhyperbolic moveout in transversely isotropic media,” Geophysics, v. 62, pp. 1839-1854.

[4] Choi, H., Byun, J. and Seol, S.J., 2010, “Automatic velocity analysis using bootstrapped differential semblance and global search methods,” Exploration Geophysics, 41, pp. 31-39.

[5] Choi, H., Byun, J., Seol, S.J., Ko, S., Kwak, J.Y. and Cha, Y., 2009, “Application of Automatic Velocity Analysis Using Monte Carlo Method,” Journal of Korean Society for Geosystem Engineering, Vol. 46, No. 5, pp. 571-581.

[6] Douma, H. and M. van der Baan., 2008, “Rational interpolation of qP-traveltimes for semblance-based anisotropy estimation in layered VTI media.” Geophysics 73(4): D53-D62.

[7] Fomel, S. and Stovas, A., 2010, “Generalized nonhyperbolic moveout approximation,” Geophysics 75(2): U9-U18.

[8] Grechka, V. and Tsvankin, I., 1998, “Feasibility of nonhyperbolic moveout inversion in transversely isotropic media,” Geophysics, 63(3), pp. 957-969.

[9] Thomsen, L., 1986, “Weak elastic anisotropy,” Geophysics, 51, pp. 1954-1966.

[10] Thomsen, L., 2002, Understanding seismic anisotropy in exploration and exploitation, Distinguished Instructor Series No.5, SEG, USA, p. 32.

[11] Tsvankin, I. and Thomsen, L., 1994, “Nonhyperbolic reflection moveout in anisotropic media,” Geophysics, 59, pp. 1290-1304.

[12] Wang, X. and Tsvankin, I., 2009, “Estimation of interval anisotropy parameters using velocity-independent layer stripping,” Geophysics, 74, pp. WB117-WB127.

Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

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