How it Works (Automatic Mistie)
The Automatic Mistie wizard performs a series of calculations to determine the best corrections to apply. The calculation varies depending on which parameters are chosen to tie: time, phase and amplitude.
To determine the time shift, phase, and amplitude for a pair of traces:
Over the calculation window:
- Calculate the cross-correlation between the traces.
- Calculate the envelope and instantaneous phase for the cross-correlation function.
- Find the peak of the correlation envelope.
- This is the optimum time-shift to correct any mis-tie, independent of phase.
- The optimal phase rotation is the instantaneous phase at this location.
- The shift and rotation is applied, then the optimal scalar multiplier is calculated to minimize the RMS difference between the traces.
How automatic mistie calculation computes its values
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For each intersection, Insight selects traces for comparison around the intersection.
- For a 2D/3D intersection, this is the specified number of traces.
- For a 2D/3D intersection, Insight selects all of the traces where the 2D line overlaps the 3D data.
- For a 3D/3D intersection, Insight chooses a random sampling of traces within the region that overlaps (or specified polygon).
- Insight calculates the optimal time-shift and amplitude scaling for each intersection independently (see above).
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In most cases — where many lines intersect each other in a complex grid — these optimal shifts and amplitude scalings cannot be applied.
- For example, if three lines intersect to form a triangle, and the amount of shift/scaling required is different at the two ends of the line, it cannot apply a single uniform correction. So Insight computes a single shift/scaling for each line that will minimise the total residual mismatch for all the lines at the end.
- Once the final time-shifts have been calculated, the optimal phase-shifts for each intersection can be calculated independently.
- As above, a single phase shift is calculated for each line or 3D volume that will minimise the total residual mistie.
- The Relative Results for QC table shows the relative corrections at each intersection.
- The Overview of Changes table shows the final absolute corrections that will be applied to every line or volume.