Importing Seismic Data

Owned by Erlend Kvinnesland
Last updated: Dec 01, 2023 by Jan Henrik Koren
5 min read

SEG-Y files

The Ground Model Add-in supports both 2D and 3D SEG-Y data.

Scanning seismics

Before performing a full import it can be a good idea to scan the seismic SEG-Y file to learn its properties. Some of these properties will be transferred to the SEG-Y import tool.

The scanner allows you to:

  • Visually inspect the file headers for useful metadata

  • Inspect any trace header to learn properties like byte positions to be set during import

  • Preview the navigation in the map directly from the SEG-Y file

To open the SEG-Y scanner:

  1. In the Ground Model toolbar, click the button SEG-Y Scanner. The scanner window will open.

  2. In the scanner window click Browse to select the SEG-Y file. Although the SEG-Y Reader currently only supports 2D seismics the scanner supports both 2D and 3D seismics.

  3. The File Headers tab in the scanner window will show the contents of the textual and binary headers. Click a row in the binary header table to view any extended information for that entry.

  4. The Trace Header tab show the contents of the trace headers. A SEG-Y file is mostly comprised of so-called traces, where a trace contains a header along with sample data. The current version of the scanner does not support viewing seismic amplitudes.

  5. To see extended information for a trace header click on the corresponding row in the trace header table on the left.

  6. Use the play-button to navigate trace-by-trace in the file. The trace table on the right will show trace header values for several traces at once, whereas the trace header table on the left will only show the current trace.

  7. To select which headers to display in the trace table check or uncheck the corresponding field in the trace header table. The corresponding column will appear or disappear in the trace table on the right.

  8. The Apply Scalars button will, when checked, apply a scalar multiplication to some of the fields in the trace header. This is for display purposes only, but gives an indication of the final values that will be used during import. The scalar itself is a number that is used as a multiplier (> 1) or divisor (< -1) to a header value to arrive at the final value. Examples of scalar are

    • Coordinate scalar

    • Elevation scalar

    • Shotpoint scalar

The scanner makes it possible to preview the seismic navigation in the map before performing a full import. Visually verifying that the navigation ends up in the right place can be a useful QC tool. The preview works by reading the navigation coordinates directly from the SEG-Y file and displaying them in the map.

To preview the navigation:

  1. Click the Map Preview tab

  2. Choose the coordinate system that applies to the SEG-Y file.

  3. Choose a target map. Note that the map must be activated before it is displayed in the pulldown menu.

  4. When choosing coordinate byte positions the trace header table should give you a good indication of which to apply.

  5. Click the View button. The navigation will appear in the target map.

 

Importing seismic

When reading a SEG-Y file it will be converted to VDS format.

The first step is to create an empty target feature class using the Create Seismic Feature Class tool in the toolbox

The second step is to import the SEG-Y and create a VDS file. Click the SEG-Y to VDS button on the Ground Model Toolbar . This will open a dialog pane where the seismic file and the output file locations are browsed in, compression method is selected together with a few other input parameters.  NOTE : Ensure that the 'ensemble' fields header values point to valid X, Y coordinate fields in the headers. VDS uses this to create the geometry. When clicking the import button the sesimic VDS file will be generated.

The Seismic Volume to Features button will open a dialog pane where your VDS 3D seismic can be imported to the feature class you created in the first step above. If your seimsic is 2D, use the VDS 2D to Features button instead of the Seismic Volume to Features button.

 

2D SEG-Y seismic can also be read in using the geoprocessing tool SEG-Y Reader. This tool will create a feature class with each feature corresponding to the survey navigation. Samples, if read, will be created as separate raster files. The feature class will contain a field called url that contains the path to these rasters. The default location is within the same geodatabase in which the navigation is created.

 

  1. In the Ground Model toolbox double-click the SEG-Y Reader tool.

  2. Fill in the input parameters

    1. SEG-Y File - Browse and select one or multiple SEG-Y files. The SEG-Y files should belong to the same survey

    2. Feature Class Location - Browse and select a file geodatabase. If you don`t have a file geodatabase you can create a new by right click inside a folder and selecting File Geodatabase

    3. Feature Class Name - Specify a name for your seismic feature class. Note that this cannot start with a numeric value

    4. Spatial Reference - Specify the coordinate system of the SEG-Y files. You can browse for a CRS by clicking the globe, or you can select one of the map layers in the dropdown and the tool will use the map layers CRS.

    5. Dimension - Specify whether the SEG-Y files are 2D seismic lines or 3D seismic cubes. Currently only 2D is supported.

    6. Endian - Most SEG-Y files have big-endian byte order. If unsure, leave it to default values.

    7. Textual header format - Most SEG-Y files have EBCDIC headers. If unsure, leave it to default values.

    8. SEG-Y sample input format - If unsure, leave it to default values.

    9. Sample output format - If unsure, leave it to default values. If set to NO_SAMPLE_OUTPUT, the tool will only import the navigation.

    10. Sample interval - Will be automatically filled.

    11. Sample interval unit- Specify whether the SEG-Y files are in Time or Depth and in which unit

    12. Delay recording time - If unsure, leave it to default values.

    13. Delay recoring time multiplier - If unsure, leave it to default values.

    14. Shotpoint byte position - The standard shotpoint position is set to 17. Technically this could be any location in the file that contains a numerically increasing value. If the shotpoint values are missing from the file, consider using the trace numbering positions 1 or 5 instead.

    15. Navigation Z values - Determines how the z-coordinate of the navigation points is assigned.

    16. X coordinate byte position - Common byte positions for the (X, Y) coordinates are (181) or (73).

    17. Y coordinate byte position - Common byte positions for the (X, Y) coordinates are (185) or (77).

    18. Inline byte position - Common byte position is 189

    19. Crossline byte position - Common byte position is 193

  3. Click Run to execute the tool. Note that reading many SEG-Y files may take a while.

  4. When finished the new feature class should appear in the ArcGIS Pro Map and Contents pane

 

To see the seismic data go to the section: https://geocap.atlassian.net/wiki/spaces/GFA/pages/2356543562