Seismic Studio Tutorial - Part 4

1
Seismic Studio Tutorial - Part 4Stack QC

• Boulder, Colorado USA
• November, 2004

2
Overview

• Stack slice QC generates arbitrary 2D lines,
  called slices from your 3D prospect.
• You specify the CMP spacing and grab radius for
  each line. Traces can therefore be multiply
  assigned to CMPs. This can take some time.
• You pick a velocity field using semblance
  analysis for each stack. This velocity field is
  throw-away it does not get exported.
• You create stacks and can look at any two stacks
  from the current slice.
• The traces you stack are the actual un-decond
  data you use for your refraction picking.

3
Stack QC Window

• Accessed under Stacks on the Menu Bar

• The Stack Slice window provides a wide range of
  functionality
• Slice selection along any arbitrary line
• Semblance velocity analysis
• Stack with and without statics
• Azimuthal limitation

4
Stack Slice Window

• Works from slices you select from your data
• Is map-driven
• Drag a line on the map to create a slice
• Set a CMP spacing and capture radius
• Creates a 2D SEG-Y file for each slice
• Slice Manager
• Delete old slices
• Select current slice from list

5
Control Pane 1 You drive the window from here
Trace and Semblance Display Pane This is where
you see everything
Control Pane 2 This contains the map and map
controls
6
Control Pane 1

• Stack display provides control over stack trace
  display parameters wiggle, fill color, trace
  excursion, etc.
• Stack filter for applying simple bandpass
  filter and some gain options
• Salience experimental lets not go there
• Auto picker experimental we are developing
  some automatic velocity picking functionality
• Azimuth for azimuthally limiting traces in the
  semblance analysis and in the stack.
• Semblance/Mute for setting min/max velocities
  in the semblance and the stretch mute percentage
• ( Bold italics indicate important, often used
  tabs.)

7
Control Pane 1

• Slice Manager this is where you select which
  slice you want to work on
• Statics for applying static corrections
• Gather filter for applying a bandpass filter
  and gain options
• Stack manager this is where you actually name
  your stacks and generate them
• Gather display provides control over stack
  trace display parameters wiggle, fill color,
  trace excursion, etc.

8
Resize bars click and drag
Change map to any value in database
9
Here we have gone to the Slice manager and see a
slice we created back in Feb, 2004.
We have pulled up the resize bar to make the base
map bigger. The black line shows the existing
slice.
10
To create a new slice simply click and drag a
line across the map.
11
You will see this dialog for creating a new 2D
SEGY file.
Then you see this information dialog.
12
This dialog comes up. There are two passes. The
first pass counts. Then space is allocated. The
second pass creates the actual SEG-Y file. The
second pass can take a while for long lines with
wide trace radii.
13
Click on these navigation buttons to move into
the line.
Select the line in the Slice manager, the line is
highlighted in red on the map.
14
Once you see a CMP gather you like, you can pick
velocities.
As you move your mouse across the gather, the
green line on the base map indicates the
shot/receiver line for each trace.
15
Left click to set velocity points.
Click D to delete the closest point to the
mouse.
16
Click on Velocity display and push the Recompute
velocity field from knees button.
17
Now you can drive the velocity analysis from
this display. Left-click where you want to pick
a new velocity point.
18
(No Transcript)
19
Go back to the Velocity display and click the
Recompute button again.
20
Break time

• So, at this point we have
• Created a slice
• Computed a velocity field.
• But our data have no statics applied, we will do
  that later. First, lets create a stack with no
  statics applied.

21
Second, click on the Stack manager tab
First, resize Control Pane 1 so you can see more
controls.
22
1. Type in the name for your stack.
2. Type in the maximum time for your stack. The
default is 1000 msec.
3. Click on Create new stack button
23
To see your stack, click on the View two stacks
tab.
Then click on the stack name in the drop down
list, and click Load.
24
Applying statics

• Now we will create a stack with statics applied.

25
Click on the Statics tab
Click on the Apply statics from the selected
header radio button.
The default header location is Static Correction
which is where your current refraction statics
are stored.
26
Recompute stacking velocities

• Now you should repick your velocities, because
  they after refraction statics are applied they
  will change.

27
We recommend repicking the velocities at the
previous locations.
The best way to do this is to zoom in (right
mouse button) on a previous location then left
click.
Click carefully on one of the dots
28
This one doesnt need much change.
29
This one should be changed, especially under 700
msec.
30
Recompute the velocity field
31
Create a new stack dont forget to name it
32
Now you have two stacks and they zoom together.
33
Conclusions

• Slice stack QC is for checking the quality of
  your statics solution.
• You can create as many stacks as you want.
• The window only keeps one velocity field at a
  time. You cannot save a velocity field to
  retrieve it later.
• You cannot export a velocity field to another
  processing system.