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Introduction

The tracking data is the foundation of all further GIM processing, including:

  • GIM seismic
  • Surfaces
  • 3D bodies
  • Facies attributes on surfaces

Note that the tracking settings are often very different for the different options mentioned above, and it is therefore essential to be aware of how to set the GIM tracking parameters to obtain optimal results.



On this page:

Tracking generation interface

The tracking generation interface in opened up from GIM > GIM Data Generation > GIM Tracking. The interface has 4 different menus and works as a wizard with next and back buttons. The 4 menus are:

  1. Input
  2. Tracking parameters
  3. Output
  4. Status

Tracking parameters


The tracking parameters menu

Tracking parameter explanations:

  • Snap mode
  • Direction
  • Gradient tracking
  • Backtrack quality control algorithm
  • Deletion
  • Average
  • Deviation
  • Amplitude range
  • dT - Time difference
  • dT - dt between best and 2nd best
  • d(dT) - Gradient
  • Look ahead

Testing tracking parameters

Knowing how the tracking parameters work will only take you so far. Wether the objective of the tracking is to generate GIM seismic, GIM surfaces or 3D bodies, it is always important to test the tracking parameters on some inlines and crosslines first. Since the tracking process only takes a few seconds on any given inline/crossline, or 2D section, it is possible to effectively test the tracker interactively until the desired result is obtained.

To test the tracking parameters, make sure a seismic section is displayed in the Geocap graphical window. Click the Select button in the input menu of the tracking generation interface, and click on the seismic section with the crosshair in the graphical window. You will see e.g ->inline2000 at the end of the seismic dataset field, when you have selected the seismic section.

Click Next and set the tracking parameters. Then click Next, Next and Run. After a few seconds the tracking will be displayed on top of the seismic section. Evaluate the result by zooming into different parts of the seismic section and look for different anomalies and breaks in the reflectors. Adjust your parameters accordingly by going back two steps with the Back button and repeat the process. When you are happy with one section, try the same settings on a few other seismic sections.

Generate tracking for surfaces

Make sure you have optimized the cube before you start generating tracking for surfaces.

Generating surfaces is very much a balancing act. One wants the tracker to be generous and generate long lines giving us large surfaces. But at the same time we do not want the tracker to make mistakes. In most cases we would sett the tracking criteria to MinMax, Both ways, Gradient tracking and Delete segments shorter than 10 traces, but if you want the tracking generation to run faster you should select only one polarity (min or max) when setting the Snap mode. As a stop criteria we normally just use dT or d(dT). Finding the right parameter to use will require some testing as explained in Testing tracking parameters, but as a starting point you can try to set dT to 8-10ms or d(dT) to 4-6ms.

After testing the tracking parameters on a few seismic lines you can track the whole cube. Go back to the input menu and edit the input settings. For most cubes we recommend using an inline and crossline distance of 100m, as a starting point. This means we would set the Interval InLine and Interval Cross Line to 8 on a cube with an inline and crossline spacing of 12.5m.

Generate tracking for 3D bodies

To make 3D bodies, we want to omit the data which is interpretable. We invert the tracking so that all good data is removed, and we are left with the noisy bits of which we will make bodies. Often we use a tracking criteria with MinMax, Increasing, no Gradient tracking and Delete segments longer than 6 traces, combined with a stop criteria of e.g. dT set to 6ms. Of course you will have to test these settings as explained in Testing tracking parameters.

As with tracking for surfaces we recommend using an inline and crossline distance of 100m, as a starting point. This means we would set the Interval InLine and Interval Cross Line to 8 on a cube with an inline and crossline spacing of 12.5m. We only generate tracking in one direction when tracking for 3D bodies, either inline or crossline. You can do this by unchecking the crossline or inline option in the output menu.

Tip

If you are looking to create a single 3D body from one specific part of the cube, we recommend you create a subset of the cube first. This will make the process a lot quicker and more convenient.

Generate tracking for facies attribute

To make facies attribute, we only generate the tracking in one direction, either inline or crossline. One recommended method to get exiting results is to combine a strict tracking criteria, e.g. a dT of 3 ms, combined with a “remove short” set to 10 traces. This will make lots of breaks in the tracking as well as remove all parts of the data where GIM cannot generate interpretation lower than 10 traces.

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