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Introduction

In order to use the sediment formulae criterion in UNCLOS Article 76, we need a dataset containing the sediment thickness. This dataset can be based on seismic data. This tutorial has some exercises which cover the basics for working with seismic data.

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Exercises

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Import SEG-Y files

This exercise will guide you through import of a seismic line. It will cover the simple case for a plain SEG-Y file which follows the SEG-Y standard and has navigation stored in the trace header. In the example we will use the SEG-Y file which is stored with the Atlantis project.

A SEG-Y file can only be imported into a seismic data folder. If you are using Geocap's standard UNCLOS folder structure then such a folder is located in 3. Sediment Data/Seismic Lines In this exercise we will also generate a sub-folder in order to organize our data.

  1. Locate the folder 3. Sediment Data/Seismic Lines in your project
  2. Right click the folder and select New > Folder
  3. Right click the folder and select Rename. Give the folder the name of the survey. In this case ATL-LOS-00 (or give it another name if you are importing into the Atlantis project and the folder already exists)
  4. Right click the folder and select Import > SEG-Y 2D. The SEG-Y import menu will appear.
  5. Click the Defaults button in order to reset the menu to the default options.
  6. Click the file browse button and select the ATL-LOS-00-1.segy-file located in the Atlantis folder structure on disk (Atlantis/data/Atl-los-1-segy).
  7. Click Open. The file follows the SEG-Y standard and we do not have to change the default settings.
  8. It might be a good idea to check that the Storage: in the lower right corner is set to 8 bit.
  9. Click Execute and the file is imported.
  10. Click close in order to close the SEG-Y import command.

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We have now set up everything we need and are ready to start interpreting. Interpreting manually:

  1. Click the button.
  2. Pick points on the seismic line by pointing the mouse cursor on the seismic line and clicking the p or <space> key on the keyboard. If you want to undo a pick, you can click the d key.
  3. When you are finished interpreting click the button.

Editing an interpretation:

  1. Click the button.
  2. Re-pick points in an area where you have picked points before. You pick points the same way as you did the first time.
  3. When you are finished interpreting click the button.
  4. Observe that the old interpretation is updated with the new interpretation.

Deleting parts of an interpretation:

  1. Click the button.
  2. Pick two points: the start- and the end point of the part of the interpretation that you want to delete.
  3. The part of the interpretation between the two points is automatically deleted.
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Interpreting with auto-tracking:

  1. To select Snap mode look at the seismic display and identify the reflector representing the seabed. Compare the color of the seabed reflector with the seismic color table. The color on the left side of the color table represents minima; the color on the right represents maxima. The seismic color table used is one of three:

  2. Select Snap mode accordingly.
  3. Select Track mode to be Auto.
  4. Set Delta Z. Delta Z is the maximum allowable vertical distance between two auto-tracked points. Z is usually time in ms. A good rule of thumb is that Delta Z should be the double of the sample interval in the seismic. In our case that is 8.
  5. Pick the horizon to autotrack by clicking the p key on the keyboard
  6. The horizon is automatically interpreted

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