We present a reconnaissance look at P-P and P-S amplitude variation with offset(AVO) effects for the Glauconite interval in the Blackfoot 3C-3D survey. Zoeppritz equations analysis from blocky models and raytrace synthetic seismograms built from three dipole sonics in the Blackfoot field predict discernible P-P (and possibly P-S) AVO effects associated with both the upper and lower porous sand channels. These effects are largely due to the anomalously low Poisson's ratio of these sands.
The Sensor processed subvolume was selected for analysis because of its smaller size and possibly higher signal band. The simple method of differencing offset limited migrated cubes to create maps of AVO anomalies. Three offset limited stacks formed from overlapping offset bins which together span the available offsets at the target time were formed for both vertical component and radial component data. The vertical component was processed for P-P reflections while the radial component was processed for P-S reflections. The six offset limited stacks were then run through a flow of time variant spectral whitening, fxy spatial prediction, and 3-D migration.
The six migrated volumes were then differenced (far-near for P-P and far-middle for P-S) and the difference volumes were inspected for AVO effects. Strong, obvious P-P AVO anomalies were found which indicate both the upper and lower channels. The top channel trend shows high lateral resolution and follows closely the trend of producing wells. The lower (Glauconite) channel is also imaged as a slightly more diffuse trend roughly 100-200 meters west of the producing oil wells. P-S AVO anomalies were also found in the channel interval with suggestive correlations but they are less interpretable due, in part, to our technique which is designed for P-P data.
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