Estimation of Thomsen’s anisotropic parameters from walkaway VSP and applications
Liu Yi-Mou1,2, Liang Xiang-Hao2, Yin Xing-Yao1, Zhou Yi2, and Li Yan-Peng3
1. School of Geosciences, China University of Petroleum (Huadong), Qingdao, 266580, China.
2. Exploration and Development Department, Tarim Oilfield Company, PetroChina, Korla 841000, China.
3. Development and Production Seismic Division, BGP inc., CNPC, Zhuozhou 072751, China.
Abstract Estimation of Thomsen’s anisotropic parameters is very important for accurate time-to-depth conversion and depth migration data processing. Compared with other methods, it is much easier and more reliable to estimate anisotropic parameters that are required for surface seismic depth imaging from vertical seismic profile (VSP) data, because the first arrivals of VSP data can be picked with much higher accuracy. In this study, we developed a method for estimating Thomsen’s P-wave anisotropic parameters in VTI media using the first arrivals from walkaway VSP data. Model first-arrival travel times are calculated on the basis of the near-offset normal moveout correction velocity in VTI media and ray tracing using Thomsen’s P-wave velocity approximation. Then, the anisotropic parameters δ and ε are determined by minimizing the difference between the calculated and observed travel times for the near and far offsets. Numerical forward modeling, using the proposed method indicates that errors between the estimated and measured anisotropic parameters are small. Using field data from an eight-azimuth walkaway VSP in Tarim Basin, we estimated the parameters δ and ε and built an anisotropic depth-velocity model for prestack depth migration processing of surface 3D seismic data. The results show improvement in imaging the carbonate reservoirs and minimizing the depth errors of the geological targets.
Walkaway VSP|Thomsen’s anisotropic parameters|VTI|first-arrival travel times
Cite this article:
LIU Yi-Mou,LIANG Xiang-Hao,YIN Xing-Yao et al. Estimation of Thomsen’s anisotropic parameters from walkaway VSP and applications[J]. APPLIED GEOPHYSICS, 2014, 11(1): 23-30.
[1]
Alkhalifah, T., and Larner, K., 1994, Migration error in transversely isotropic media: Geophysics, 59(9), 1405 - 1418.
[2]
Alkhalifah, T., and Tsvankin, I., 1995, Velocity analysis for transversely isotropic media: Geophysics, 60(5), 1550 - 1566.
[3]
Blias, E., 2009, Long-offset NMO approximations for a layered VTI model: Model study: 79th Ann. Internat. Mtg. Soc. Expl. Geophys., Expanded Abstracts, 3745 - 3749.
[4]
Blias, E., 2010, Interval anisotropic parameter estimation above the receiver array in walkaway and 3D VSP data: 80th Ann. Internat. Mtg. Soc. Expl. Geophys., Expanded Abstracts, 243 - 247.
[5]
Grechka, V., and Tsvankin, I., 1998a, Feasibility of nonhyperbolic moveout inversion in transversely isotropic media: Geophysics, 63(3), 957 - 969.
[6]
Grechka, V. and Tsvankin, I., 1998b, 3D description of normal moveout in anisotropic inhomogeneous media: Geophysics, 63(3), 1079 - 1092.
[7]
Grechka, V. and Tsvankin, I., 1999, 3D moveout velocity analysis and parameter estimation for orthorhombic media: Geophysics, 64(3), 820 - 837.
[8]
Hornby, B., Miller, D., Esmersoy, C., and Christie, P., 1995, Ultrasonic-to-seismic measurements of shale anisotropy in North Sea well: 65th Ann. Internat. Mtg. Soc. Expl. Geophys., Expanded Abstracts, 17 - 21.
[9]
Isaac, J. H. and Lawton, D. C., 1999, Image mispositioning due to dipping TI media: A physical seismic modeling study: Geophysics, 64(4), 1230 - 1238.
[10]
Larner, K. and Cohen, J., 1993, Migration error in transversely isotropic media with linear velocity variation in depth: Geophysics, 58(10), 1454 - 1467.
[11]
Li, J., Li, Y., and Guo, X., 2010, VTI medium test-firing ray tracing: Oil Geophysical Prospecting (in Chinese), 45(4), 491 - 496.
[12]
Newrick, R. T., Lawton, D. C., and Spratt, D. A., 2000, Multi-offset VSP traveltime inversion for anisotropy analysis: 70th Ann. Internat. Mtg. Soc. Expl. Geophys., Expanded Abstracts, 2237 - 2240.
[13]
Sadri, M., and Jamali, J., 2010, Estimation of anisotropy parameters from offset VSP data: 72nd EAGE Conference & Exhibition, Barcelona, Spain, Expanded Abstracts, P282.
[14]
Stunff, Y. L., Grechka, V., and Tsvankin, I., 2001, Depth-domain velocity analysis in VTI media using P-wave data: Is it feasible?: Geophysics, 66(3), 897 - 903.
[15]
Supriyono, Priyono. A., Triyoso, W., and Prasetya, L., 2012, Velocity versus offset (VVO): a new tool for direct detection of gas in low-impedance sand reservoirs: First Break, 30(4), 59 - 68.
Tang, X., and Chunduru, R., 1997, Inversion of shear-wave anisotropy from cross-dipole logging data: Method and case study: 67th Ann. Internat. Mtg. Soc. Expl. Geophys., Expanded Abstracts, 270 - 273.
[18]
Tsvankin, I. and Thomsen, L., 1994, Nonhyperbolic reflection moveout in anisotropic media: Geophysics, 59(8), 1290 - 1304.
[19]
Tsvankin, I., 1995, Normal moveout from dipping reflectors in anisotropic media: Geophysics, 60(1), 268 - 284.
[20]
Tsvankin, I., 1996, P-wave signatures and notation for transversely isotropic media: An overview: Geophysics, 61(2), 467 - 483.
[21]
White, J. E., 1983, Underground sound: Application of seismic waves: Elsevier, New York, USA, 56 - 81.
2014, Vol. 11 
