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Using Trace Maths and Two Attribute Volumes to Highlight Targets

Claude RibordyDavid WorsickSimon Voisey

Introduction

We show how specific data can be extracted from two volumes using independent data ranges and then provide an unique trace value for each range. See table right

In our example, we have acoustic impedance and porosity volumes.

AI units: m/s*g/ccPorosity units: Fractions

Trace value 2 is to illuminate our area of interest

All remaining data3

AI: 8000->11000Porosity: >0.1

2

AI: 0-> 8000 Porosity: >0.1

1

ConditionsTrace Value

The data-sets

Image at right shows the Porosity volume in the panner, with the acoustic impedance volume as the background.The black dashed line illuminates a channel, which is our area of interest. Trace value 2, from previous slide’s table, exhibits our channel lithology.

0.15

0

Porosity

Acoustic Impedance

Step 1

With both volumes in the same window, select “Trace-Maths” from the “process” menu

Process -> Utility -> Trace Maths…

Step 2

[1] Type A and B for the input volumes.

[2] Select “used” for each volume so they will be used in the trace maths operation

A and B are referenced in the trace maths script

[1] [2]

Step 3

Choose appropriate output name

Step 4

If required, you can crop the output volume in terms of the grid’s inline and xlinecoordinates

Step 5

Each output trace value has a particular line of code in the script, as shown here

Trace maths script

The ScriptvolumeA = A;volumeB = B;

trace = volumeA * 0.0;

i = 0;

while ( i < numsamples(volumeA) ){

/* Setting trace to 3 everywhere, */trace[i]=3;

/* except if condition 1 is met, */if(volumeA[i]>0 && volumeA[i] <8000 && volumeB[i]>0.1)

trace[i]=1;else{

/* or condition 2 is met */if(volumeA[i]>8000 && volumeA[i] <11000 && volumeB[i]>0.1)

trace[i]=2;}i = i + 1;

}

trace;

Step 6

[1] First “Load” the Two_volume_targeting.prs file downloaded from the trace maths examples section on our website

Reconfigure the script in the expressions window using your desired parameters.

[2] “Save” the updated script for future reference

[1]

[2]

Step 7

Finally click “OK” to output volume

Step 8

Initially the volume is shown in traces. This is impossible to interpret so we need to show the volume in colour and generate a new colour key

First click the “eye-ball” as highlighted by the red box

Step 9

Set the trace data to none and make colour data the recently generated trace-maths volume

Step 10

[1] Select the “Colour-key” tab

[2] Reduce number of colours.

I advise 2 colours per output trace values. i.e. 3 trace values in the volume, therefore 6 colours are required in my example

[1]

[2]

Step 11

Double-click on each colour bar to alter its colour

Step 12

Yellow is my first trace value colour

Step 13

Final colour selection for each trace value

[1] We now need to change the data range

[1]

Step 14

In my example I set the range from 1->3

Step 15

Next we save the colour key

Step 16

Provide an appropriate name for the colour key

Step 17

Now in the plot tab [1]…

…[2] Change the lateral colour resolution options as shown.

[1]

[2]

Results

In this final image we see the porosity volume in the panner and the newly generated traces of the math volume in the background.

We see no evidence of trace value 1 lithology, however trace value 2 lithology, our channel, is illuminated and shown by the black-dashed line

Porosity

Trace-maths Volume

Results

Trace value 1 and trace value 2 lithology is seen further up our section, as shown right