AGM 5
lecture 4
lecture 4
Kartei Details
| Karten | 26 |
|---|---|
| Sprache | English |
| Kategorie | Naturkunde |
| Stufe | Universität |
| Erstellt / Aktualisiert | 09.01.2013 / 10.01.2013 |
| Weblink |
https://card2brain.ch/box/agm_5
|
| Einbinden |
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diffraction hyperbola
.
migration does what
uses velocity information to zip up hyperbolae
repositions energy reflected from dipping layers
what signals don't migrate
multiples
out of the plane diffractions
etc.
how does predictive deconvolution work
If we can identify the input wavelet, and replicas of it, we can attempt to suppress those replicas
how to remove multiples post velocity analysis
the same as pre velocity analysis
SRME
surface related multiple estimation
Earth responce
source generates multiples, every multiple is a source etc.
big pro and big con of SRME
3D SRME is enormously intensive but you don't need to know anything about the veocity:depth model.
ISRME
internal surface related multiple attenuation
what does ISRME do?
SRME only looks at free-surface multiples ISRME includes short-paths into the Earth Response.
why would time variant filtering be necessary?
as seismic energy spreads out its frequency reduces, so one bandpass filter cannot serve for all frequencies
lots of migration algorithms, why
they work in a slightly different way, each suited to different subsurface make ups, and cost different amounts
Kirchhoff migration uses...
Huygen's Principle, finds where the energy went
Wave equation migration works...
opposite tp Kirchhoff migration, predicts where the energy may have come from.
Three types of migration
Kirchhoff migration
Wave equation migration
F-k migration
F-k migration works...
data transformed to F-k domain, and migrated based on relationshop between unmigrated dip angle of reflector and migrated dip angle of reflector.
how to spot an out of plane refection event
[in 2D data]
cross cutting event
(but be wary of OWC cross cutting events)
benefit of 3-D migration
Although 3-D acquisition and processing is more expensive we don’t need as high a fold-of cover.
CIP
common interval point
when are CIPs good?
when all CIP gathers are pre-stack migrated, constructive interference occurs at true reflection points
pre-stack vs. post-stack migration
pre is expensive as every trace in CMP has to be migrated.
However 3D pre stack migration as computer power and complexity of subject area increases
"migration" is more strictly termed
time migration
depth migration...
more accurately and automatically depth converts
cutting edge workflow
(4)
3D
pre-stack
reverse time
depth migration
Fresnel zone
The zone in the subsurface that contributes to a recorded amplitude
Fresnel zone informs...
spatial resolution
