Similarity Mapping

Similarity Mapping - Overview

You can open the Similarity Mapping dialog box in three ways. Open the Seismic window and do one of the following:

Similarity maps compare a pilot trace to other traces on 2D and 3D datasets in your project. They are useful as quick look reconnaissance tools for rapidly high-grading the areas of interest in your seismic data. You will typically use cross-correlation coefficients as the principal comparison technique when creating a similarity map, but you can use several other comparison techniques. You can summarize your results using ranking maps.

Follow these steps to create a similarity map:

Select the location of the gate. You have the following options:

The easiest way to define your gate is to use this dialog box in conjunction with the caliper tool in the Seismic window.

Select the Fixed Time Gate option to center the gate on a specified time. WinPICS selects a default time value based on the location on the seismic where you right-clicked to open this dialog box. Collapsed View image

In the Fixed Gate Time Window section, select the start and end time for fixed gate data.

Choose the Use a Horizon as Time Gate Center option to center the gate along a selected horizon, which will be used as time zero. Collapsed View image

If you select this option, the Similarity Mapping dialog box changes to include a field for Gate Center Horizon. Collapsed View image

Click the Gate Center Horizon list and select a horizon to center the gate on.

Choose the Use 2 Horizons to Define Time Gate Window option to center the gate between two selected horizons. Collapsed View image

If you select this option, the Similarity Mapping dialog box changes to include fields where you can select the gate start horizon and gate end horizon. Collapsed View image

Select the start and end horizon from each list.

In the Defined Time Gate Window for Correlation section, define the allowable gate search window. You have the following options:

Gate Center - Type the value (in milliseconds) for the time to center the gate on.
Gate Each Side - Type the value for the time to use as a window above and below the gate center.
Gate Offset - Type the value for the time to use to offset the gate center.

In the Correlation Calculation Option section, select the correlation options. You can set values for the following fields:

Search Window for Max Correlation +/- in ms - Type a value to define how many milliseconds to allow time zero to shift when looking for the maximum correlation.
Minimum Calculation Result Threshold for Picking - Type a minimum threshold to filter your results for the amplitude field.
Maximum Calculation Result Threshold for Picking - Type a maximum threshold to filter your results for the amplitude field.
If you type 100 for the Minimum Threshold and 200 for the Maximum Threshold, ProductName will output only amplitude values between 100 and 200. All values outside that range will not be picked. If you select Minimum Threshold and Maximum Threshold values of 0, then all values will be output.
Time Window Adjustment - You have three options in this list:

List Option	Description
Time-Correlation Coeff. Max	Select this option if you want ProductName to calculate the time when the maximum cross-correlation value is found. This maximum value is measured from time zero of the seismic data set.
Time-Envelope Max	Select this option if you want ProductName to calculate the time when the maximum cross-correlation envelope is found. The maximum envelope is the time at which you would get the best tie if the seismic trace were phase adjusted to the plot.
Time-Input Time	These windows display the start and end time for fixed gate data, as determined by your selections in this dialog box. These windows only appear if you selected Fixed Gate as your gate location.

Matching Method to be Used - Select from the list of methods you can use to generate your correlation.
Use Absolute Value of Cross Correlation - Select this check box to have ProductName consider negative and positive values to be equal.

In the Output Horizon section select the horizon to use in the calculation. The data you generate with this process will be stored on the horizon you select here.

Click OK. Similarity maps are stored and posted on the map as amplitude.

Correlation Method vs Covariance

Time-Correlation Coefficient Max - Select this option to have ProductName return the time where the maximum cross correlation value is found. This is the time measured from time zero for the seismic data set.

Covariance Method - Output covariance amplitude when you want to see relative amplitude comparisons with your pilot. Since covariance is not normalized, it is sensitive to amplitude differences and will highlight instances where the waveform shape is constant but has amplitude changes, such as a porosity change in a thin bed.