Amplitude versus offset (AVO) interpretation is based on the assumption that angle-dependent reflection coefficients in prestack seismic data are proportional to reflection amplitude.
Therefore, the goal of AVO processing is to ensure that prestack data represent the true offset dependent reflectivity. This is done by preserving the true amplitude of the data throughout processing, by compensating for the amplitude distorting effects inherent in the seismic method, and by accurately datuming and imaging reflections to their proper position in time and space.
Geokinetics’ AVO processing sequence is defined based on an analysis of the input data, and incorporates available well log data early in the processing for amplitude verification, velocity calibration, and choice of deconvolution parameters. As far as possible, all processes are deterministic and surface consistent, and can handle complex statics, noise and multiples in the land or marine environment. We also rely on the latest anisotropic technology to extend the effective AVO utility of the data to the maximum possible offset/angle ranges.
Depending on the AVO attributes desired, Geokinetics has the ability to invert all relevant linear approximations of the Zoeppritz equations including, but not limited to:
|Linear approximations and attributes|
|R.T. Shuey||Normal Incidence (Ro), Gradient (Go), curvature|
|J. L. Fatti et al.||P-wave reflectivity, S-wave reflectivity, density reflectivity|
|D. Gray||Lambda reflectivity, mu reflectivity|
|R. Verm and F. Hilterman||Poisson reflectivity, Normal Incident reflectivity|
|Angle stacks, offset stacks, etc.|
|G. Smith and M. Gidlow||Normal Incident P-wave and S-wave reflectivities|
The estimation of new attributes can be implemented as needed.
In addition to the AVO Attributes listed above, other AVO products are available:
- AVO Inversion of reflectivity volumes or Simultaneous Inversion of CMP gathers into impedance volumes. Impedance volumes and products include AI, SI, EI, EEI, GI, lambda-rho, mu-rho, AIGI, etc.
- X-Ray Volume based or horizon specific X-plot, Rotation and Assessment of AVO attributes from near- and far-angle volumes can be approached to better enhance the differences in the petrophysical properties being analyzed. Other AVO attributes or Inversion volumes can be substituted for the near- and far-angle volumes.
- Seismic Wide Angle Processing (SWAP) is available if sufficient offset ranges are available and data quality is adequate. While all data sets are pre-stack migrated, NMO corrections are not applied until after a horizon has been selected. This avoids wavelet stretch and permits tuning analyses. With SWAP processing, the AVO effects of fractures is greatly enhanced. Offsets greater than 3 times depth are possible to use in high-resolution AVO analysis with favorable field conditions.