Refraction Statics
Bryce Hutchinson
Sumit Verma
how much correction will be applied to the source and receiver!
3D Statics display
2. Right click in the
window that opens.
Under 3D Display View,
click Statics View
1. Click this button on the right side of
the statics window to open a 3D
statics display
3. This display shows the static shift, in milliseconds, for individual shots
and receivers throughout the survey. Click and hold to rotate the image
and scroll to zoom in or out.
Refraction Statics
1. Return to the refraction
statics window by clicking the
icon next to your primary
dataset
4. Click over to the shot
info tab. Be sure that
Surface Source is
selected since our
source is a Vibroseis
truck. Click OK
2. Click to the “O” for options at
the top left of the window
3. Change the refraction
replacement velocity to 5500
5. Click Ss and Rs to calculate the
shortwave and refraction statics.
1. Save your static results to a text file.
3. Click the green plus next to Sort Data
Tools at the bottom of the Project Data
Sets window
2. Close the window
4. Change the name of the sort and the
main and secondary sort keys
Statics Flow
1. Now we will create a statics flow. I’ll
run through the settings for each flow
command.
2. Set the input to
the raw data
3. In the sort tab, change
it to the sort we just
created
Statics Flow
Notice here we have not calculated elevation
statics. So, currently total statics is refraction
statics!
3. In StatShft,
set the Vista
Defined
Header Static
as Static_Total.
It should
default as this.
1. In the ReadStatics flow command, Click File and choose
the text file that we saved earlier in the refraction
window.
2. Be sure the Source and Receiver Static Headers are set
as above.
4. Save your statics file output and throw
your name on there like Sumit! Click GO to
run the flow.
NMO Flow
3. Define the sort as CMP_NO
1. Set It is time to create a
normal moveout (NMO) flow
4. Read in the
velocity file
that you
created in the
semblance
window. It
should be the
only option.
5. Apply an NMO Stretch Mute
2. Set as the
input the
static file we
just created
6. Name your output! Click GO
to run the flow
1. Run the flow again, but this
time use the raw data as the
input. Keep everything else
the same.
Next we will stack each of
these datasets we just
created.
CMP Stack
2. Set sort
to CMP_NO
1. Set the
input as the
NMO Static
applied data
3. Right click Input
and Data/Headers
Selection
4. Click the 3D icon
then the Green plus.
Then match the Inline
and Crossline values
to those below.
5. CMP Stack
settings should
appear as such by
default
CMP Stack
1. Don’t forget to save your output file!
2. Repeat the same simple stack flow for
the raw dataset with NMO applied to it.
When you finish, you will have two stacked datasets.
Both stacks will have NMO performed on them, but
one will have statics applied and one will not.
You can see our comparison on the next two slides.
Compare the data before and after
statics applied!
NMO Stack – no statics
2-12
NMO Stack – statics applied
2-13
Points to note!
• You can test for different refraction velocity and see how does it affect your
(Compare before and after refraction statics applied!)
– Shot gather
– NMO corrected Gather
– Stacked data set
After refraction statics, we expect the reflectors to be better flattened on the NMO gather .
Here, refraction statics does not show much effect, and probably you can find a better refraction
velocity by trial and error.
•
Refraction statics and elevation statics are some of those processing steps on
which, you must take advice from an experienced processer.
We expect you to know how to generate these images!!
Ask for help if you can not!
Raw- no NMO
Statics applied no NMO
Raw – with NMO
Statics applied with NMO