Importing Seismic Data

Owned by Erlend Kvinnesland
Last updated: Oct 28, 2024 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

  • See file statistics

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

  • Preview SEG-Y file amplitudes

  • Import only navigation

  • Generate rasters (JPEG, PNG or TIF) from amplitudes

Using 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. 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. To see extended information for a trace header click on the corresponding row in the trace header table on the left. Use the play-button to navigate trace-by-trace in the file. The trace table on the tab to the right will show trace header values for several traces at once, whereas the trace header table on the left tab will only show the current trace. 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 tab to the right.

  5. 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:

  • In the Coordinate Settings section (under the Trace Headers tab), select byte positions to read for trace index, and X/Y coordinates positions. Tick of Coordinate Scalar Override if necessary

  • Is the seismic of interest 3D also select byte positions for in- and crosslines.

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

  • If the coordinates in the file are given as seconds of arc, tick of Convert from seconds of arc.

  • In the Map Preview section, select the traces to be visualized. Also select if the navigation should be displayed as points or lines (Geometry Type).

  • Hit View to display the navigation in the map.

  1. In the Header Statistics tab, the file can be scanned for file statistics. For example, x/y coordinates equal to zero can be detected, or consecutive ensemble number values can be checked to see that the increment is 1 throughout the file.

  2. Previewing the seismic amplitudes can be done by loading the samples in the viewer in the Samples tab. To display the file as desired it is possible to zoom in/out, fit preview to viewer, se full size and pick color table. Use the sliders in the statistics tab to adjust the displayed data range. In the coordinates tab set the domain and unit, set delay recording time and apply scalar. When Apply Scalar is checked a scalar multiplication to some of the fields in the trace header will be applied. 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

If the Ground Model Project contains grids, grids intersecting the seismic profile can be visualized along with the sample preview by ticking off Show surface intersections in the Display tab.

  1. The seismic navigation can be imported as features, with or without accompanied amplitudes as rasters (TIF, PNG or JPEG). This is done under the scanner Import tab. If not already done, browse in the SEG-Y file of interest. If only navigation is needed, select Import navigation as features. Select Import samples as raster(s) if needed, either with or without the navigation features. Select the target feature class for the navigation and target folder for the raster(s). The data range from the samples viewer will be applied when generating the sample raster(s) if the Use current clip range from samples viewer in the options section is ticked off. Click the Import button. The navigation feature and raster(s) will be written to their respective targets.

 

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 found in the pull down menu under the SEG-Y to VDS button on the Ground Model tool bar.

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. The file locations could be local or in cloud storage (see Cloud Support). If working with cloud storage, established connections can be found in the dropdown menu. If a new connection is needed, simply click “new” to make a new connection.

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: Visualizing data