5 - Loading SEGY Seismic
Clean up the SeisX names
Run the awk move.ak by creating the file junk that contain all files that end in .segy and then run the awk move.ak. Be sure you are in the segy subdirectory.
$ pwd D:/Projects/indexa/segy $ ls 101.segy 103.segy 105.segy 107.segy 2d.fmt 102.segy 104.segy 106.segy MOVE.AK $ ls *.segy > junk $ awk -f move.ak < junk > jobBefore you run job, I suggest you examine the file first. (use the more command). This awk can be used to "clean up" far more complicated line names. This additional step save us effort as we load the data! awk is an extremely powerful text manipulator. We are running the program awk that takes it's input from from the file move.ak, operating on the file junk and places the output in the file job.
more job mv 101.segy 101 mv 102.segy 102 mv 103.segy 103 mv 104.segy 104 mv 105.segy 105 mv 106.segy 106 mv 107.segy 107 [job](EOF) $ ./job $ ls 101 103 105 107 job 102 104 106 MOVE.AK junk $Note that the Korn shell under Windows NT requires the ./ to execute this Korn script.
Load SEGY from disk
Select Project, Load Data from Disk, 2D segy, Add files, select segy directory and change the wild card to "*". examine file 101. Select the input format file as 2d.fmt. Set the Display type to MIG, type in "Raw data" in the file description String, toggle on the Interpolate shot points and UTM's. Press the (Set Line Names & Display Type) button, and press (ok). You do not need to fill out the Line Names. SeisX will default to the external file names. That's why we renamed our files!
Select then Press OK and the Statistics
button, Start trace 1 and 1000 traces. Toggle Use IBM FP for statistics,
compute histograms, pre scan files and extract headers, apply.
Examine the Histogram Statistics looking for a normal distribution of data.
(Create /Update Base Map) will
extract the map information from the SEGY files and compute the line
intersections. If you are running version 3.4 or older, the program will beep
when lines have different time sample intervals. We will learn how to
batch process the data the next chapter to resample to a common 4ms.
(Project Statistics), Normally, the RMS scaling is all over the place
and ranges from 300 to 200,000. These data need scaling and re sampling. It is
a good idea to check the XY's. Make sure they look reasonable. Sometimes they
are stored 10 or 100 times larger. Sometimes the first or last point may be
zero. The navigation SEGP file will be used to correct for this error
Individual line statistics can be examined by clicking on (Statistics)
Using a SEGP file to correct XY locations
If the line coordinates are obviously incorrect they will need to be updated.
It is usually a good idea to check the first and last shot point to see that
they agree with the first and last shot point in the SEGP data file. If
they are not within a couple of shot points, a paper section will need to be
retrieved to correct the shot points and X,Y locations. Select
(Project), (Import Survey Information), (Seg-P Format).
(File) course.segp.dat, be sure to let the (UTM Scaling) to default, (Select
All Files), (Load) File (Create Update Project map...). This last step will
rebuild the base map.
Attaching a SeisX'd 3D
Next step is to "attach" our 3D data volume. Select, project, attach SeisXed
files, segy directory,ok. The 3D should be located on the north east of our
study area. Tie the 3D line to the 2D line 103 using the 
Seismic Display option. Press the 
button to select line 103 with the left mouse button finishing with the right
mouse button. Toggle the 2/3 button again and extend the line into the 3D
volume through to Well-O. Your color table may be all wrong. Select (Color),
(Adjust VD Seismic) and (Load...) the default.spl color table. Be sure to
press the (Apply Here) button so all future windows will use this color table.
If you Background color is not to your liking, select (Color), (Adjust Wiggle
Trace Colors), (Background). I like setting the background to a light gray.
Press the RGB button and slide the vertical lines equally under the Red, Green
and Blue color scales. Be sure to press the apply here button.
Adjust the time shift between the two data sets by holding the Ctrl button
down as you use the left mouse button to move the 2D up and down to produce an
exact alignment. Notice the high frequency content and high signal to noise
ration of the 3D. This 3D was shot with dynamite in 1998 and is less than half
the fold of the 2D vibroseis data set from the early 1990's. There appears to
be some phase differences between the 2D and 3d. Notice the
obvious reefing at Well-O. Can we find any other reefs with this data set?
Normally your seismic data would not be scaled properly.
You may need to select the Seismic
Display Attributes, change start time to 0, Scaled Display to 100,000 and time
scale to 5.0. It is a good idea here to change the Well Template to
sonic-gamma.template. It will be used for all subsequent windows. Be sure to
(Update System Display Attributes) so they will be reflected in subsequent
windows.
When should I use Panther's Software?
It is recommended to use SeisX to load all SEGY data. It had been noticed that several problems exist when Panther's SDL has been used for both 2D and 3D directly into SeisX data format. Note: Data converted from Landmark using SDL may have problems with subsequent time slice generation. Load all data directly into SeisX from SEGY! Use Panther to convert Landmark to segy and load that format. Converting directly into SeisX may cause problems!
Who can convert my SEGY data?
The SeisX SEGY has established itself as the standard in Calgary. Until SeisX became established, every company had it's own SEGY standard. The only complaint I have had concerning SeisX is the fact that Shot Points and XY's are stored as floating point! Perhaps it is time for the Society of Exploration Geophysicists to update their standard!
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