Specifying Keywords and Data Locations (ASCII Volume)

This step is very important: here you tell the ASCII Volume Loader where to find information that defines the data and locations of the traces in the volume.

Although there is a well-defined ASCII standard, most software (or companies) define their own settings that don't entirely conform to the standard. These customised settings are often described in the text header, but not in a machine-readable format.

Common formatting

Use the delimiter to parse the data columns.

The files can provide a header with description of the contents of the file, history of the data, and important headers. This is for user reference and is not used by the loader, they must be skipped for the loader to only read the data.

Velocity volumes: VELF

VELF format is a file format which has been a carrier for seismic stacking velocity data. It can provide a header with description of the contents of the file, history of the data, and important headers. This is for user reference and is not used by the loader.

The VELF file is grouped into shotpoint/common mid point (CMP) (2D) and inline/crossline (3D) velocity series. The key term is usually “SPNT” (this can vary) which indicates a new data point. Each row is a physical location and can include X,Y,Z coordinates (not required).

Please note that the loader will only accept CMP based data for 2D volumes.

The next key is “VELF” (this can also vary), where we have our time and velocity data. The “time” columns and “velocity” columns are placed next to each other.

Assigning Keywords

Remap headers for vertical extents
Remap headers for vertical extents

There are two types of keywords that must be assigned: those that define the horizontal extents and those that describe the vertical extents of the volume.

  1. Those that define the spatial extent come from the keyword for CMP (2D) or IL/CL (3D) that is usually SPNT.
  2. Those that define the vertical extent come from the keyword for Velocity Data that is usually VELF.
  3. You can select the correct keywords or type a custom keyword that matches the file.
  4. Click the appropriate dropdown box and assign the index to IL/CL (3D) or CMP (2D). Note: If unsure, consult the data provider for the correct locations.
  5. Type the first data columns in the first and second VELF line onwards.
  6. Click Previous/Next line to go to the next file (if multiple files were selected).
  7. Click Next and the loader will retrieve:
    • the set of Inline and Crossline values used in the data (3D)
    • the set of CMP values used in the data (2D)
    • any invalid or suspect data

Velocity volumes: DISKOS V98.1

The DISKOS V98.1 format is sorted into columns for shotpoint/common mid point (CMP) (2D), inline/crossline (3D), time/depth and velocity series. It can include X,Y,Z coordinates (not required).

This format is commonly in seconds (s) instead of milliseconds (ms), please select the unit accordingly.

Please note that the loader will only accept CMP-based data for 2D volumes.

Assigning Columns

There are two types of keywords that we must assign: those that define the horizontal extents and those that describe the vertical extents of the volume.

  1. Those that define the spatial extent are usually labeled as CMP (2D) or IL and CL (3D).
  2. Those that define the vertical extent are usually labeled as TWT and Velocity.

Assign these columns with the data type accordingly or use "Header lines skipped" option to get to the data. You may also want to consult the data provider for the correct locations if necessary.

Velocity volumes: ESSO V2

The ESSO V2 format is sorted into columns for shotpoint/common mid point (CMP) (2D), inline/crossline (3D), time/depth and velocity series. It can include X,Y,Z coordinates (not required).

Please note that the loader will only accept CMP based data for 2D volumes.

This format can come with additional characters either as a prefix or a suffix for CMP (2D), inline and crossline (3D). Use the character skip tool to get only the relevant data by typing the characters to strip.

There are two types of keywords that we must assign: those that define the horizontal extents and those that describe the vertical extents of the volume.

  1. Those that define the spatial extent are usually labeled as CMP (2D) or IL and CL (3D).
  2. Those that define the vertical extent are usually labeled as TWT and Velocity.

Assign these columns with the data type accordingly or use "Header lines skipped" option to get to the data. You may also want to consult the data provider for the correct locations if necessary.

Velocity volumes: Custom (Column-based)

Similar to above the data is sorted into columns for shotpoint/common mid point (CMP) (2D), inline/crossline (3D), time/depth and velocity series. It can include X,Y,Z coordinates (not required)

Please note that the loader will only accept CMP based data for 2D volumes.

There are two types of keywords that we must assign: those that define the horizontal extents and those that describe the vertical extents of the volume.

  1. Those that define the spatial extent are usually labeled as CMP (2D) or IL and CL (3D).
  2. Those that define the vertical extent are usually labeled as TWT and Velocity.

Assign these columns with the data type accordingly or use "Header lines skipped" option to get to the data. You may also want to consult the data provider for the correct locations if necessary.

Upon clicking Next the loader will retrieve:

  • the set of inline and crossline values used in the data (3D)
  • the set of CMP values used in the data (2D)
  • any invalid or suspect data

Genuine offer of assistance

DUG understands that importing ASCII volume data can be a confusing task.

Whether you are using a trial version or a fully-paid licence, we will help you to import your data to Insight so that you will get the maximum out of your data.

For more details, contact support at [email protected].