Reading Geometry spread information from ASCII file format

Theory

During the seismic data acquisition, all the field related information is recorded in Observer logs. In the observer logs, the field geophysicist records the shot & receiver information, receiver spread, uphole time, uphole depth, no of channels, spread configuration, sweep information (in case vibroseis), total no of channels, shot and receiver intervals, near and far offsets etc.

In case of the latest acquisition surveys, all these observer logs are well documented and available in standard formats. In case of the vintage data, these are hand written on papers. So the user has to digitize them by means of typing into a text editor or an excel sheet to create a spread sheet with all the required information for assigning a geometry.

The module loads ASCII file and creates a spread table. Format of the input observer log should be like the following :

• Shot Point
• FFID
• First channel in the left branch of a gather
• Last channel in the left branch of a gather
• First channel in the right branch of a gather
• Last channel in the right branch of a gather
• Weight of explosive
• Shot Depth
• Uphole time
• Dead Traces
• Shot offset

Input data

Input observe log file should be provided in the Parameters tab.

Parameters

Observed logs file

Provide the input observer log file.

Measurement system { Feet, Meter }

Choose the corresponding measurement system from the drop down menu.

File type { Tab delimited, Space delimited, CSV, Manual }

 Select the input file type from the drop down menu.

The module can work with the following types of format:

       1. Tab delimited - columns are delimited by a tab

       2. Space delimited - columns are delimited by SPACE

       3. CSV - columns are delimited by Comma

       4. Manual - columns location can be defined by the user

Total channels expected

Provide the total number of channels in the survey/line. By default, 1. In case the total number of channel is not set, a warning message will pop-up.

Automatic header detection - If checked, this option will automatically detects the headers information from the input ASCII file for Tab delimited, space delimited and CSV file formats.

Header row

This parameter looks for header row information. Specify from which row the headers information starts from. It is usually 1st row.

Start row

Starting row of the input observer log file.

File read parameters

This section deals with the reading of the input geometry file from where it detects the columns information.

File read parameters manual

This section deals with the individual columns information. The user should manually mention the positioning of the each individual information against it.

FFID

provide the corresponding FFID column position from the input observer log.

Src line

Provide source line position

SP

Shot Point starting and ending column position

Rcv line

Receiver line position

RP 1

1st receiver point column position

RP 2

2nd receiver point column position

RP 3

3rd receiver point column position

RP 4

4th receiver point column position

Weight

Specify the source weight column position if available

Depth

provide uphole depth column position

Uphole time

 provide uphole time column position

Dead channels

specify dead channels starting and ending column position

Reverse channels

specify reverse channels start and end column position

Perpendicular offset

specify perpendicular offset column position if available.

Inline offset

provide inline shot offset column position

CDP

provide CDP column position

Live traces

live traces column position

Remark

remarks if any available in the observer log file, specify the start and end column position.

Error checks

This section deals with the error checking of the input observer log file.

Double ffid check

By default, FALSE. If checked, it will check the duplicate FFID.

Double src sp check

By default, FALSE. If checked, it will check the duplicate Source Shot Points.

Settings

Skip

By default, FALSE(Unchecked). This option helps to bypass the module from the workflow.

Output data

Spread

Generates the spread information.

Spread table

This module generates the Spread table. This spread table is used in "Geometry application" module to reference/connect to Spread table information.

File

Outputs the observer log in a file format.

Information

There is no information available for this module so user can ignore it.

Examples

In this example workflow, we've added load geometry from ASCII and Load observer logs from ASCII module. These two modules are required for Geometry application in case the geometry spread and navigation is not available in any of the standard navigation formats like SPS, SEG-P or P190.

Provide the input observer log file and set the appropriate parameters. This module generates the vista items like Spread table, spread file etc.

As we mentioned earlier, this module generates the Spread information which is used to connect/reference to Geometry application module.

Actions

There are no action items available for this module so the user can ignore it.

Video lesson

YouTube video lesson, click here to open [VIDEO IN PROCESS...]

Related articles

Yilmaz. O., 1987, Seismic data processing: Society of Exploration Geophysicist

* * *   If you have any questions, please send an e-mail to: support@geomage.com  * * *