Load data and Geometry assigment

Now we can create the first workflow (or geophysicists usually call it job) for converting input SEGY file into the internal date base and geometry assignment. In the g-Platform window in Workflow tab click on

icon (1) and define a workflow name (2) 0001_Load_and_geometry. There is an option to use jobs examples or templates (see a Templates tab) where you can find all necessary jobs according to the common seismic processing sequences.

Open the job (g-Navigator window) by double click on it and add a module for reading SEGY file and it's QC. Use right mouse button (RMB) click on the Module Manager area -> Modules Inside -> Input/Output -> Read SEG-Y traces:

Notice that you have many modules for reading input data sets, so use them according to the task. For example, read one SEGY file or several SEGY or SEGD files, etc. In this tutorial we are using Viking Graben seismic data: a marine seismic data acquired in North Sea that is accessible on the internet free as a open data. Also we are using open source UKOOA P1/90 (Falcon 2D survey) data provided by Geoscience Australia.

1) Read SEG-Y traces. In the module's parameters we need just select the input file seismic.segy via Seismic filename (1) parameter and launch the job by double click on the module or click on button

(2). Current 2D line does not require powerful hardware, so performing will be fast. A progress bar and some statistic (errors, log, etc.) during and after calculation you can find at the bottom of GNavigator window.

Trace headers were read from the SEGY file and it is possible to check EBCDIC, binary and trace headers. Open all VistaWindows by RMB on the module -> Vista Groups -> All groups -> In current window:

Now only two windows are filled with the information: EDCDIC and binary headers.

If we need to visualize more input data (QC windows) from SEGY file it is reasonable to use View SEG-Y module.

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Be careful with the Saving mode = Append, in this case each time you execute module, each time it is adding seismic traces to the previous file, in other word 2 times run will lead to duplicates traces in output 0001_Iput_SEGY_2D file. To avoid the problem use RewriteFile mode.

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Module Manager	This is where the user add/delete the processing modules to build the workflow
Module Properties	Input the data parameters
View Manager	To see the visual contents of the processing modules like input/output/difference, location map etc.
Vista Items From DB	A place where the user can save the vista items (like stack sections or input/output/difference ) for future reference.
Output View	Records the scheme of events i.e. if the user modifies any parameter it will make a note of it in the Output view as an event but doesn't show what are those modifications.
Progress View	Displays the progress of the workflow when executed. It displays the % completed, which process is currently running etc.

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Do not save seismic from SEGY into internal data base before geometry assignment!!! (i.e. do not use Save

Otherwise, you will lose some trace header information! Therefore ,we must use Read SEG-Y traces, prior

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The next step after conversion SEGY file into the internal date base is geometry assignment and quality control. g-Platform provides workflow (job) templates for seismic processing sequences with all necessary modules, vista (visual) windows and parameters.

Since we saved the SEGY data into g-Platform internal data, we should use Read seismic module instead of Read SEG-Y traces. Connect all input and output DataItems. The geometry workflow will be consist of the following modules as shown on the picture below.

In normal case, we do not have geometry information in traces headers, therefore we have to do geometry assignment by using two modules: read seismic by Read SEG-Y traces (Read seismic traces) and read navigation file by Load geometry from UKOOA P/190 module. BUT, the Viking Graben data comes with geometry assigned and all the headers information is available in the trace headers. Here we are showing the workflow(s) for both the scenarios:

The next workflow without the navigation module due to the fact that the input data is already geometry assigned. However we are adding an additional module called Correct SP numbers (2D) to correct the SP number prior to Binning 2D. If an input data with geometry, then we have the following workflow:

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Data Item is an input or output data set which is located in the Input data and Output data tabs.

Data Item may be seismic traces, sorted headers, velocity model, static corrections and so on.

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Input and output connections may have different names: Data Items / Vista Items / Data Vectors, but the meaning is the same, it is just some input and output data sets from one module to another:

1) Read seismic traces loads seismic trace from the previous step, input file name is 0001_Input_SEGY_2D. Execute the module by double click on it or press on run button

from the upper menu. Do not need to open vista views for this module, because we already have done it in the previous workflow.

2) Correct SP numbers (2D) performs the renumbering or correcting the source and/or receiver numbers. Once the module is executed, the new source/receiver numbers will be updated into the trace headers. In the Type correction, the user can select the whether they want to correction Receiver or Receiver and source from the drop down menu. By default it is Receiver.

3) Binning 2D Now we have geometry information inside seismic trace headers, so the last step is to calculate slalom line for binning 2D and update CMP numbers and coordinates.

This module creates geometry for 2D seismic data set where traces are grouped together by their sub-surface positions into common midpoints (CMP). For visual quality control, the module creates several vista views for binning quality control.

1. Filter midpoints by maximum trace offset value. Only midpoints that have an offset less than or equal to a user specified value will be used.

2. Build the grid. A direct line is drawn from the first source/receiver location to the last source/receiver location. The line is then divided into segments, with each segment being the grid size of the slalom line as defined by the user.

3. Build the slalom line. The set of midpoints are divided into groups using the grid increment previously defined. The center point of each midpoint group is determined, these points are connected and become the slalom line.

4. Smooth the slalom line by using the slalom smooth parameter and the topography smooth window parameter.

5. Build a crooked line using the crooked line increment parameter. The first point of the crooked line is the first source/receiver bin center point and the last point of the crooked line is the last source/receiver center point location.

6. Build a stack line using the stack line step parameter. This is the CMP spacing. The first point of the stack line is the first center point and the last stack point is the last center point. The user assigns the number of the first CMP and these will then increment by one

7. Filter midpoints with a maximum distance between the MP and CMP point parameter.

• Create binning – create a sub-surface geometry using parametrization of current module;

• Import binning from SEG-Y – use a sub-surface geometry from specified SEG-Y input data set;

• Import existing crocked line from ASCII file - it allows to import an existing crooked line from an ASCII file. For example, a crooked line which was built and used by other processing companies/software’s during data processing. The advantage of this option is in using all information of binning from the input file, the parameters of the module in this case are not in use;

The crooked line file in ASCII format should include the following information, 3 columns: CDP number, CDP-X and CDP-Y coordinate of previous result.

Crooked line bin increment

Maximum offset to include in binning

Only midpoints that have an absolute offset distance less or equal to the specified value will be used in the binning process;

Grid size of slalom line

Slalom smoothing distance

Topography smoothing distance

Crooked line factor

If import binning from txt file option is chosen, this parameter is used as decimation factor;

Max distance between midpoint and CMP point

First CMP number

It is recommended that this parameter be 2 times the number of the first live receiver station number. That makes it easier to relate a CMP number to its position relative to the station numbering of the line;

First CMP shift

Import crooked line:

Crooked line input file - Full path name of the text or SEG-Y file that will be used for binning if a Binning type option other than Create binningis used;

Skip import errors - If checked, ignore errors of importing crooked line;

Forced sort stack line - If checked, reverse the stack direction.

Add all vista group in a new window. Look at CMP Topography window, there are two elevation lines: original relief and smoothed one. Smoothed elevation it is a float datum that you will use on the further processing steps, for example velocity estimation, etc.

4) Save seismic. The final step in this workflow is saving seismic traces with all geometry information in headers: SOURCE_X, SOURCE_Y, RECEIVER_X, RECEIVER_Y, OFFSET, SOURCE_SP, RECIVER_SP, SOURCE_ELEV, RECEIVER_ELEV, CDP, BIN_X, BIN_Y, BIN_ELEV, ...

We can stop at this point and go the next chapter or continue with extra QC module which is might be useful to check geometry.

We are briefly describing about Load geometry from UKOOA P1/90 module to read the navigation data even though it is not part of the workflow, i.e. if an input data without geometry, then we should use new modules: Load geometry from UKOOA P1/90 and Geometry application:

Load geometry from UKOOA P1/90 module imports navigation files from ASCII into the processing system. Go to Input data of the Load geometry from UKOOA P1/90 module and browse the input P190 file from the file browser. Select the file and click Open. The system by default looks for ".dat" file. So please select Files of type as All files (*) so you can to see all the .P190 files.

In the module properties, it automatically extracts the line name from the input P190 file.

Measurement system - By default Meter. Select the survey measurement system from the drop down menu.

Coordinate scalar - Specify the coordinate scalar in case if it is not 1. By default it is 1.

Inline offset - In case the survey was designed that there is a deviation of inline offset then provide the inline offset information

Moving Src/rcv - In case the source and/or receivers are moving then select the appropriate one from the drop down menu. By default, Sources.

Update GUI table S - By default checked. It will generate the Source table information.

Update GUI table R - By default unchecked. If checked, it will generate the Receiver table information.

Update GUI table X - By default checked. It will generate the relationship table information.

There is an option for displaying source and receiver coordinates on the map, S, R, X spreadsheets (tables), source and receiver elevation graph. Execute the module by double click on it or press on this run button

from the upper menu:

Then add all visual windows called VistaGroups on your work area: press RMB on the module -> Vista Groups -> All groups -> In current window. Now you can look through all visual windows and check SPS files:

After executing the module and displaying the Vista items, the following Vista items will be displayed as shown below. The user can rearrange them as per their choice by simply hold with MB1 or LMB, drag it to the desired location and release the mouse button.

We can change the display parameters of the location map, Source elevation and Receiver location map by clicking on the Show properties

of respective window. To do that, first select the Receiver points. After that the corresponding Vista item properties will appear. Make the changes like Point type, Point color, Point size etc. Here we are changing the Point Color of Receiver points. We can see before and after changing the Point color from Blue to Green.

Geometry application is designed for assigning geometry on land and marine 2D/3D seismic data, checking geometry, also manual trace editing is implemented there. The trace headers are filled in accordance with input geometry files, but without binning (binning will be perform on the later stage by using binning 2D/3D modules). The process of geometry assignment is divided into three following steps:

2) Geometry assignment (Connect geometry from the Load geometry from UKOOA P1/90 and the original file trace headers and SEG-Y data handle);

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Geometry Application is a standalone module, and does not need to be run inside a Seismic loop.

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Velocity – set to an approximate Linear Move Out LMO velocity. This is QC tool and will not be applied to your data;

Dead trid – Change this number if the trace ID marker of your data for dead traces is something other than 2;

AUX TRIDs – Some data sets have additional auxiliary traces that are marked with special trace IDs. You can indicate that here.

Display all the Vista groups for the module (press RMB on the module-> Vista Groups -> All groups -> In new window.). There are three basic categories of vistas in Geometry application: Tables, Maps, and Traces.

You may click on any entry in a table, or any location on a map, and that point will be highlighted or displayed in all other views. Use the Table Errors Vista to check mis-matches between geometry files and the seismic data set;

•Use the Action Items associated with Geometry application to view the shots, receivers and field files in auto-mode/movie (Key slide, Sources slide, Receivers slide) or one by one (Key prev, Key next, Source prev, Source next, Receiver prev, Receiver next);

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Not every module has an action menu. Only advanced modules like application or interactive

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Go through all source gathers and check geometry by comparison first arrivals on traces with the linear velocity function (red line), check the offset distribution on the Map SP-Offset location window, look at all tables and make sure you don't have any critical problem with geometry.

•Table Errors - vista displays mismatches between the original seismic file and geometry files;

•Table Changed Points - displays points that have been moved, including their new and former positions;

•Table Spread, and Table FFID RAW - display the spread/relation and raw FFID numbers respectively;

•Table Sources, and Table Receivers - display the source and receiver numbers and its coordinates. You may remove shots or receivers (mark all the traces as dead) by right clicking on that entry in the table and selecting Kill Shot or Kill Receiver;

•Table Killed Sources, and Table Killed Receivers - display all the shots and receivers killed (marked as dead) by the user. Killed shots or receivers can be revived by right clicking on an entry in these tables and selecting Revive.

•Map FFID location, Map Sources and receivers elevations and Map SP-Offset location, which display various cross plots of geometry characteristics;

•Map Sources and Receivers Location display location of shots and receivers on a map, allow to move those points from one location to on another if necessary. See Moving Points. Use these views to verify positions of sources and receivers and move them (see moving points).

You may move the physical location of a shot or receiver point on the map by using the Map Sources and receivers location.

Use the

button on the vista tool bar for the Map Sources and receivers location Vista, choose Current Source Moving Point and Selected Source.

Right mouse click and hold on the source point you would like to move. Drag the point to its new location. The previous location of the source will be indicated by its original marker (default: Red triangle), and the new location will be indicated with new marker (by default, a semi-transparent red circle).

When you move some source point, the Velocity display on the Gather Source view will be updated and it reflects a new source point location.

The source point marker will be updated with its new location when you click on the new point again, or on a different source point.

Try to move the point so that the velocity display aligns with the traces on the Gather view. The peak of the velocity function should match up with the nearest first arrivals – this is a good indication that your source point is positioned correctly.

•Gather key, Gather Receiver, and Gather Source, which display the traces of the currently selected key, receiver, and source. You may edit individual traces in these views.

•Use the Trace Editing feature to reverse trace polarities, or mark problem traces as dead.

For trace editing: choose gather display source, receiver or sorted gather, select the type of trace marker you would like to set. Make sure only one option is checked off at a time.

To set a marker, right click with the mouse, or right click and drag across several traces.

Traces will not be removed or changed until you save the resulting data set using Save Seismic or Save SEG-Y.

Go into the Vista properties of the view to adjust the size and color of the trace markers, to make it easier to see which traces are flagged:

Once you have performed all geometry edits, run

the Geometry Application module. Geometry will be assigned: output traces headers are updated, dead traces are removed from the data set.