3. Designing and Saving the Spectral Blueing Operator

3. Designing and Saving the Spectral Blueing Operator
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Various parameters exist which allow the Geoscientist to perturb how the operator is generated. In SsbQt these changes occur in real time so you will be able to see immediately the effect of the change you have made. Pop up the "Design Controls Dialog" by either clicking the Design Controls... menu item under the Tools menu bar or by clicking the icon.

Design Controls Dialog	List of controls
	Smoothing Seismic Mean This controls the amount of smoothing that will be applied to the seismic mean spectra. The operator length is specified in Hertz. Fit Well Log Curves These spinboxes control the lower and upper boundaries for the principal curve fit. Outside this range the curve is, by default, extrapolated on the lower end and forced to be horizontal on the upper end (with smoothing applied in the vicinity of the boundary). Other curve fitting controls are available via the icon or Tool->Advanced Controls... menu item. Design Operator By default, the low and high cut points are automatically determined. You can override these settings manually by unticking the checkbox to the left of the Low Cut and High Cut spinboxes. This will sensitise the Low Cut and High Cut spinboxes allowing you to set the lower and upper cuts of the derived operator. You can also specify the slope of the operator on the low and high sides by unticking the checkbox to the middle Auto Calc. checkbox and specify the frequency of the -60 dB down points on the low and high sides. By default, operator length is also automatically determined. Here the operator length is truncated to the nearest zero crossing to give a percentage energy captured during the generation of the time domain operator above 99.9%. You can override this default by unticking the checkbox to the left of the Num. Zero X-ings spinbox. This will sensitise the Num. Zero X-ings spinbox allowing you to manually adjust the length of the operator in multiples of number of zero crossings. A facility is provided to automatically QC the derived operator. This is achieved by applying the operator to the alternative set of random traces from the same seismic data volume and charting the derived residual operator in the "Residual Operator (QC)" chart. We are looking for the residual operator to be centred around zero and essentially flat. By perturbing the Low Cut and High Cut spinbox controls within the "Design Operator" group, you can usually maximise the bandwidth in such a manner without significant residual correction either end (see figure below for example of a corrected chart).

Design Controls Dialog

List of controls

Smoothing Seismic Mean
This controls the amount of smoothing that will be applied to the seismic mean spectra. The operator length is specified in Hertz.
Fit Well Log Curves
These spinboxes control the lower and upper boundaries for the principal curve fit. Outside this range the curve is, by default, extrapolated on the lower end and forced to be horizontal on the upper end (with smoothing applied in the vicinity of the boundary). Other curve fitting controls are available via the icon or Tool->Advanced Controls... menu item.
Design Operator
By default, the low and high cut points are automatically determined. You can override these settings manually by unticking the checkbox to the left of the Low Cut and High Cut spinboxes. This will sensitise the Low Cut and High Cut spinboxes allowing you to set the lower and upper cuts of the derived operator. You can also specify the slope of the operator on the low and high sides by unticking the checkbox to the middle Auto Calc. checkbox and specify the frequency of the -60 dB down points on the low and high sides.
By default, operator length is also automatically determined. Here the operator length is truncated to the nearest zero crossing to give a percentage energy captured during the generation of the time domain operator above 99.9%. You can override this default by unticking the checkbox to the left of the Num. Zero X-ings spinbox. This will sensitise the Num. Zero X-ings spinbox allowing you to manually adjust the length of the operator in multiples of number of zero crossings.
A facility is provided to automatically QC the derived operator. This is achieved by applying the operator to the alternative set of random traces from the same seismic data volume and charting the derived residual operator in the "Residual Operator (QC)" chart. We are looking for the residual operator to be centred around zero and essentially flat. By perturbing the Low Cut and High Cut spinbox controls within the "Design Operator" group, you can usually maximise the bandwidth in such a manner without significant residual correction either end (see figure below for example of a corrected chart).

The above briefly describes the steps involved in analysing and designing a Spectral Blueing operator. The figure below shows a typical SsbQt main window with default charts re-arranged in five columns

Figure 3.3. Seismic Spectral Blueing main window after analysis and design

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