9 - 3D Interpretation
Using 2D to tie 3D
When I get a brand new 3D survey, I like to tie to existing 2D control. Select
the (Display Seismic) icon, (ArbLine 2D/3D Lines), select 
to toggle to the 2D data, select a piece of line 103, toggle back to the 3D
picking mode and select a segment through Well-S. Use the 
icon to inster Well-S into the seismic line.
Synthetic Well Ties
We
have already tied 2D data with a synthetic. We will now tie our 3D volume to
our synthetic. Select sonic-gamma.template and display use (ctrl) left mouse
button to match up the synthetic to the data. Transfer the interpretation from
the horizons on the 2D to the 3D. If the auto picking does not work, check the
Search Gate Window and ensure that it is not set to 0. Nine ms is a good value
to use for this data.
Update system parameters for all future windows.Stretch Squeeze
Use the Stretch Squeeze option to tie the well
Click the left mouse button to connect peaks together from the seismic to the
well tie. Select the (TD Calibration mode)
and verify that the drift is
less than 10ms (we did not stretch squeeze very much).
Select (Time-Depth), Define Active Time Depth Curve
by clicking on the well from the base map. This will automatically select
the well.
Select (Active), select TDPairs (our stretch squeeze)
Select (Dismiss), (Dismiss). Test the synthetic tie by bringing up another seismic line through this well. The tops and deviation curve should be in the correct position.
Horizon interpretation
Select (Horizon),(Pick Horizon), (Add/Current), DNVG
Change color to Green, Options, and Event type to peak
Change the frame increment to 50 . Select a cross line and press the middle
mouse button to interpret the horizon in both directions.
Select an in line and press middle mouse button to auto interpret the horizon.
Change the inline increment to 20. Note that displaying inlines is very much
faster than displaying cross lines. Add a BVLK horizon, color Magenta and
interpret. Note: Horizons only button will update the horizon display without
having to re rasterize the seismic display! It is now east to interpret between the in line and cross line. To speed up interpretation even more we can use the
multi line display which will load the selected increment of lines into
memory.
Auto Picking
Pick the Blue Peak with the middle mouse button. This is auto picking.
Return to the inline display and Refresh
See how the picked NRDG on the cross line is copied without having to re
raster the whole seismic screen. Increment the image by 20 and pick the data
set
Use the left and right mouse buttons to control the picking direction. Apply
to see your coarsely interpreted map
Multi Line Animation Interpretation
Set the start frame on an even number and set the Frame Increment before you
Display the data. All the selected data is rasterized and it easy to flip
between frames
This will take about a minute to create.
Creating a cube and "Blasting" an horizon
Select (Horizon), (Blaster), Interactive Map update and horizon
Select (Parameters), Blaster Mode Correlated 60, and Threshold 60
Here is the picture of a partially "blasted" data set to the left.
The complete "Blasted data" set is displayed to the right.
Now blast the NRDG horizon. It is much faster if you do not display the interactive update option. When this is complete do an Horizon Update on a line that has not been picked to verify that the automated pick is correct. Notice that there are some gaps picked in the DNVG but the NRDG and CMBR events are picked pretty cleanly. These blasted horizons will be used for time slice generation and to map an isochrons. (time interval)
Check a few more lines to verify "blasted" data. Do we have some sort of
pinnacle on the south east part of the survey area? Notice the drape over the
structure and the abrupt truncation of the lateral events. I wonder how
shallow this reef has grown?
Time Slice creation (structure and flattened)
Select Active horizon as None to create a structure time slice. Create a time
slice volume flattened on the CMBR Pick.
Auto Picking Poor Data
Blasting an horizon is a great way to go when you have high quality data. How do you pick a weak event? Or how do you pick data poor data in just part of the survey. I use the ability to grid and contour to rapidly pick events. Here are the steps I use:
- Pick the Horizon on a series of inlines
- Transfer the picks onto a coarser grid of cross lines
- Create a polygon to define the area I will be interpreting
- Grid and contour this horizon at twice the cross line spacing. Use the contour map as a quality control tool to point our areas of bad picks
- Transfer the grid onto a seismic horizon
- Snap this new horizon to the correct pick
- Grid and contour this new horizon. Check the picks!
Set the inline increment to 20,Click on map to select a series of lines, press the Make Map Selection to obtain the values, edit them and display seismic. Be sure to change the increment counter to 20 when the Seismic Display comes up
If you move the
mouse cursor over the little green dots at about time 1280, SeisX will
identify the horizon DNVG.
only to
transfer these new picks onto the cross lines.
You should see many more horizon "dots" on the display.Use multi frame again to pick every 20th inline starting at Line 270. This will infile our initial interpretation
option. Add/Create Layer..., call the new layer 3doutline,
Draw Polygon/Polyline, Dark Green, Thick.
The contour map is to the right. I have adjusted the Minimum Maximum Ribbon
values to User 1150 to 1220 in the Map Attributes window to generate this
display. Our contours look reasonable. The only problem I see is with the end
of the 2D line 103. It sure looks like it is picked too shallow! Change the
Ribbon Display to 
and make sure that
there are not any holes in our grid.
Input of DNVG and call the Output Horizon dnvg, Overwight Picks, Apply. Check
a few seismic lines not previously picked.
and the Search gate
to 10ms and press the Snap & Extract button. Update the Seismic with the
icon. Notice that SeisX does not require
to re rasterize the complete display!
few more spots on our map. Grid and contour the dnvg_SNP horizon. These
detailed contours can help you check your map! If you are brave with your
interpretation, I'd Rename it back to the original DNVG!
Transfer the dnvg_SNP grid to lines 103 and 107. Notice the static
problems that exist as end of line effects. The pick from the 3D is red and
the DNVG is yellow(active color) The picks should be flat! The
moral of the story is to be careful interpreting the ends of seismic lines
Amplitude Extraction
Select (Horizon), (Horizon Computations), Select the 3D survey 300, and add 11 ms from NRDG_BL (Blasted Nordegg) and store the output as nrdg+11
Check a 2D line to insure your "new" subtracted horizon is in the correct
time position.
Select the Map Attribute button and display the Extracted amplitude for this
new event at the triassic level
Select (Apply). The higher amplitudes are red, the lower blue.
It should now be easy to map the Nordegg Porosity event in the trough below
the Nordegg.
Note that the amplitudes are displayed to the closest sample (4ms) where as
the Time slice is interpolated to the closest microsecond. The culture lines
can be edited on the map display and not on the time slice.
Note: click on any screen picture and you will have the full size image. Press (Alt) and the left arrow and you will return to the document.
Go to the next, previous section, Table of Contents