TY - JOUR
T1 - Scanning anisotropy parameters in horizontal transversely isotropic media
AU - Masmoudi, Nabil
AU - Stovas, Alexey
AU - Alkhalifah, Tariq Ali
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors would like to thank KAUST and Rose project for their support. They would also like to thank Igor Ravve and an anonymous reviewer for their comments and suggestions that helped improve this paper.
PY - 2016/10/5
Y1 - 2016/10/5
N2 - The horizontal transversely isotropic model, with arbitrary symmetry axis orientation, is the simplest effective representative that explains the azimuthal behaviour of seismic data. Estimating the anisotropy parameters of this model is important in reservoir characterisation, specifically in terms of fracture delineation. We propose a travel-time-based approach to estimate the anellipticity parameter η and the symmetry axis azimuth ϕ of a horizontal transversely isotropic medium, given an inhomogeneous elliptic background model (which might be obtained from velocity analysis and well velocities). This is accomplished through a Taylor's series expansion of the travel-time solution (of the eikonal equation) as a function of parameter η and azimuth angle ϕ. The accuracy of the travel time expansion is enhanced by the use of Shanks transform. This results in an accurate approximation of the solution of the non-linear eikonal equation and provides a mechanism to scan simultaneously for the best fitting effective parameters η and ϕ, without the need for repetitive modelling of travel times. The analysis of the travel time sensitivity to parameters η and ϕ reveals that travel times are more sensitive to η than to the symmetry axis azimuth ϕ. Thus, η is better constrained from travel times than the azimuth. Moreover, the two-parameter scan in the homogeneous case shows that errors in the background model affect the estimation of η and ϕ differently. While a gradual increase in errors in the background model leads to increasing errors in η, inaccuracies in ϕ, on the other hand, depend on the background model errors. We also propose a layer-stripping method valid for a stack of arbitrary oriented symmetry axis horizontal transversely isotropic layers to convert the effective parameters to the interval layer values.
AB - The horizontal transversely isotropic model, with arbitrary symmetry axis orientation, is the simplest effective representative that explains the azimuthal behaviour of seismic data. Estimating the anisotropy parameters of this model is important in reservoir characterisation, specifically in terms of fracture delineation. We propose a travel-time-based approach to estimate the anellipticity parameter η and the symmetry axis azimuth ϕ of a horizontal transversely isotropic medium, given an inhomogeneous elliptic background model (which might be obtained from velocity analysis and well velocities). This is accomplished through a Taylor's series expansion of the travel-time solution (of the eikonal equation) as a function of parameter η and azimuth angle ϕ. The accuracy of the travel time expansion is enhanced by the use of Shanks transform. This results in an accurate approximation of the solution of the non-linear eikonal equation and provides a mechanism to scan simultaneously for the best fitting effective parameters η and ϕ, without the need for repetitive modelling of travel times. The analysis of the travel time sensitivity to parameters η and ϕ reveals that travel times are more sensitive to η than to the symmetry axis azimuth ϕ. Thus, η is better constrained from travel times than the azimuth. Moreover, the two-parameter scan in the homogeneous case shows that errors in the background model affect the estimation of η and ϕ differently. While a gradual increase in errors in the background model leads to increasing errors in η, inaccuracies in ϕ, on the other hand, depend on the background model errors. We also propose a layer-stripping method valid for a stack of arbitrary oriented symmetry axis horizontal transversely isotropic layers to convert the effective parameters to the interval layer values.
UR - http://hdl.handle.net/10754/622599
UR - http://onlinelibrary.wiley.com/doi/10.1111/1365-2478.12464/abstract
UR - http://www.scopus.com/inward/record.url?scp=84994910631&partnerID=8YFLogxK
U2 - 10.1111/1365-2478.12464
DO - 10.1111/1365-2478.12464
M3 - Article
SN - 0016-8025
VL - 65
SP - 981
EP - 991
JO - Geophysical Prospecting
JF - Geophysical Prospecting
IS - 4
ER -