AGM 4
lecture 3
lecture 3
Set of flashcards Details
| Flashcards | 32 |
|---|---|
| Language | English |
| Category | Nature Studies |
| Level | University |
| Created / Updated | 09.01.2013 / 09.01.2013 |
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binning
the process of resorting shot gathers into CMP gathers
another name for normal moveout velocity
stacking velocity
What does dix's equation do
use two stacking velocities to estimate the interval velocity in the material between the two reflections
RMS velocity is for
velocity through multiple layers
as VRMS is approximate...
output velocites are called stacking velocity
If you allocate the correct velocity to a reflection event you can
flatten its curvature across the offset range
(NMO)
constant velocity panel
CMP Gather is NMO corrected with different stacking velocities
problem with using constant velocity panels
need to do it individually for each CMP gather, time consuming
semblance
used for?
a measure of coherency
coherency of a hyperbolae to the wavelets in a shot gather
semblance analysis is used to
match the best stacking velocity to describe the curvature of a reflection
contoured semblance diagram
.
dixs equation states
difference in velocity*time/difference in time
relationships between
VST
VRMS
VIS
VINT
V ST approximates V RMS, and V IS approximates V INT
Where V ST is used to approximate interval velocity, we use...
VIS
interval stacking velocity
fold of cover?
The number of traces that are present in a CMP gather
The number of traces that are present in a CMP gather is termed
fold of cover
gernerally, the greater the fold of cover...
the greater the noise supression
how much does FOC boost the SNR?
FOC1/2
Field of cover, signal to noise
long path multiple image
.
stacking velocities of multiples compared to deeper events
velocities increase with depth, so multiplesexpress a slower stacking velocity.
if there are multiple peaks in a semblance panel which is which
the slower semblance peak corresponds to the multiple
why would you get two peaks on a semblance plot
where there are obvious multiples in the CMP gather
how does NMO remove multiples?
they stay curved after NMO, so stacking cancels them out
how does NMO affect quality of data?
Application of NMO corrections introduces NMO stretch
NMO corrections necessitate
NMO stretch mute
when are NMO stretch mutes applied
mutes applied where extention >30%
static correction
/
static time shift
corrects for varitations in reciever elevations; shifts all traces to some datum
residual statics
tweaks stacked traces to heal gaps in reflectors that are considered coherant
how does iterative analysis work
initial velocity analysis
initial residual statics
velocity analysis
residual statics
etc.
floating datum statics
(as opposed to)
static corrections in a CMP gather
(final datum)
floating datum
(image)
.
VINT
internal velocity
