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Synthetic AVO |
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Surface Seismic AVO Calibration |
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Service: Walkaway VSP, 3D VSP
AVO gradient and intercept
volumes derived from surface seismic data are used by the
interpreter to provide quantitative answers regarding
reservoir size, location, and fluid saturation levels.
While they provide good spatial coverage, the seismic
amplitudes recorded on the surface have traveled twice
through the sediments overlaying the reservoir. These data
were affected by scattering and attenuation, and are also
subject to variation due to the heterogeneity of the
overburden. There are many uncertainties inherent to
surface seismic AVO. These uncertainties may manifest
themselves in an erroneous reservoir model.
To reduce these uncertainties, a borehole seismic AVO
survey should be run to calibrate the surface seismic AVO
data. Because the VSP receiver can be placed very close to
the reservoir, many of the uncertainties associated with
surface seismic AVO are eliminated.Having an in-situ receiver
results in a one-way seismic travel path. Consequently,
reflection amplitudes recorded in a VSP AVO survey are
much less affected by transmission loss and scattering. In
addition, with a properly designed VSP survey, wider
reflection angle apertures can be acquired than with
surface seismic geometry. |
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Benefit and Applications
- Reflection Angle to offset correlation
- Surface to VSP trace amplitude calibration
- Synthetic AVO Response from well log data
- AVO attribute analysis
- Angle trace gather, two-way time section
- Amplitude variation with offset/angle
cross-plot
- Gradient versus intercept cross-plot for AVO
classification
- P-wave intercept trace (P), Gradient trace
(G)
- Quick AVO synthetic from P and G and AVO
synthetic stack
- Regression coefficients or standard
deviations of curve fit on AVO
cross plot
- Combinations of intercepts and gradient
traces, Poisson’s ratio, shear,restricted gradient, product, and
math-traces
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