I have a gather volume
and I want to understand the
amplitude variation with
offset at an event
Zooming in, I can see the event here
The wiggle overlay really
highlights the change in amplitude
If I turn on the amplitude graph
I can see the values across the gathers
The first panel shows a
clear increase in amplitude
and this is interesting
but the other panels show
inconsistent and negative amplitudes
The graph displays the amplitude at a constant time
and this misses the event in the other gathers
gathers because of changes in structure
I don’t want to investigate one gather at a time
so instead, I will pick the event as a gather horizon
The interpretation can follow both the structural changes
and any residual move-out in the gathers
For the best results
I should interactively pick
some gather seed horizons
and use Insights automated propagator
but for now I just need something
fast and simple
I have a horizon already interpreted on a full stack volume
creating a gather horizon from this stack horizon
will take only a few seconds
The stack horizon is here in the map view
and you can see the intersection displayed on the
gathers as a red dot at offset zero
It ties the near offsets nicely
and does a good job of following the variation in structure
Using a map operation
I can create a gather horizon
by extrapolating the stack
horizon across the gather
The input horizon provides
the vertical position
and I provide the gather type
range and increment
which can be found on the volume details panel
There!
Taking only a few seconds to create
the new gather horizon is the flat
line across the gather
starting at the zero-offset intersection
The thicker orange amplitude graph
shows that the extracted values
are much more consistent compared
to the thinner red constant-time extraction
This would be a great solution
if these gathers were perfectly flat
but I can see a small amount
of residual move-out
If I track the event exactly
I can improve these results even further
In an ideal world
I’d have the time to flatten the gathers
with some RMO correction
I could even interpret the horizon across the gathers
using the automatic horizon propagator
but let’s try a faster workaround
Using the Snap horizon operation
I can shift the picks to land on the peak amplitude
Check the gather horizon is selected
and then the gathers
I’ll set the window parameters to largest peak
with an asymmetric search window
based above the event
and constrain the output to my area of interest
There that's better
The subtle changes in amplitude can be seen on the
thick purple amplitude plot
when compared to the original flat orange horizon
It would be wise to QC a few
other locations to make sure the snap
snap function has worked well everywhere
The snap process can be run again
as a second pass to constrain any mispicks
Once checked
the gather volume can be selected in the map
and the offset amplitude can be extracted on the fly
to determine the lateral continuity
of any observed anomalies
I can interactively drag the offset location
in the gather view from a near to a far offset
That's interesting
the increase in amplitude observed on the
first gather location seems to only
occur in the southern part of the dataset
Elsewhere the amplitude decreases with offset
This is exactly the information I have been looking for