3-D moveout velocity analysis and parameter estimation for orthorhombic media
- Colorado School of Mines, Golden, CO (United States)
Orthorhombic symmetry describes several azimuthally anisotropic models typical for fractured formations, such as those containing two orthogonal crack systems or parallel vertical cracks in a VTI (transversely isotropic with a vertical symmetry axis) background. Here, the authors present a methodology for inverting multiazimuth P-wave reflection traveltimes for the parameters of vertically inhomogeneous orthorhombic media. The approach is based on the general analytic representation of normal-moveout (NMO) velocity as an ellipse in the horizontal plane. A minimum of three differently oriented common-midpoint (CMP) lines (or a wide-azimuth 3-D survey) is needed to reconstruct the ellipse and thus obtain NMO velocity in any azimuthal direction. Then, the orientation and the semiaxes of the NMO ellipse, which are dependent on both anisotropy and heterogeneity, can be inverted for the medium parameters. To carry out parameter estimation in vertically inhomogeneous orthorhombic media, the authors apply the generalized Dix equation of Grechka, Tsvankin and Cohen, which operates with the matrices responsible for interval NMO ellipses rather than with the NMO velocities themselves. Application to a synthetic multiazimuth P-wave data set over a layered orthorhombic medium with depth-varying orientation of the symmetry planes verifies the accuracy of the inversion method.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 354439
- Journal Information:
- Geophysics, Journal Name: Geophysics Journal Issue: 3 Vol. 64; ISSN GPYSA7; ISSN 0016-8033
- Country of Publication:
- United States
- Language:
- English
Similar Records
Moveout inversion of P-wave data for horizontal transverse isotropy
Nonhyperbolic reflection moveout for horizontal transverse isotropy