Seismic Anisotropy: Basic Theory and Applications in Exploration and Reservoir Characterization
by Ilya Tsvankin and Vladimir Grechka
Duration: Two days
Intended Audience: Intermediate and Advanced levels
Prerequisites (Knowledge/Experience/Education Required): The course is designed for both graduate students majoring in applied geophysics and more experienced geophysicists working in research, technical service, or exploration. Attendees are expected to be familiar with the basics of seismic wave propagation and data processing.
The most critical step in extending seismic processing to anisotropic media is to identify and obtain from the data the medium parameters responsible for measured reflection signatures. Therefore, the course emphasizes parameter estimation for transversely isotropic and orthorhombic subsurface models using both conventional narrow-azimuth data and wide-azimuth surveys. A description of P-wave time and depth processing for VTI (transversely isotropic with a vertical symmetry axis) media is followed by analysis of the joint inversion of P-waves and converted PS-modes which can yield the true vertical velocity needed for depth imaging. Field-data examples illustrate the improvements achieved by anisotropic migration algorithms and the possibilities of applying anisotropy parameters in lithology discrimination. The part devoted to anisotropic AVO analysis includes simple analytic approximations for reflection coefficients as well as for amplitude distortions (geometrical spreading) in the overburden. The course also introduces fracture-detection methods based on the azimuthal variation of reflection moveout and prestack amplitudes of P- and PS-waves.
The course should be useful for both graduate students and geophysicists working in exploration or reservoir monitoring. Mathematical details are kept to a minimum, but familiarity with the basics of elastic wave propagation and seismic data processing would be helpful.