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Loading of the data/conversion
Demultiplexing
Editing
Geometry
Amplitude correction
Frequency filter
Deconvolution
Velocity analysis
NMO/DMO-Correction
Stacking
Migration
MeasurementsNavigation
Printing/storage Printing/storage
CMP-Sorting Prestack
PoststackPost-processing
Pre-Processing
Basic scheme of the seismic data processing
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DMO (Dip move-out)
A seismic processing operation to correct for the fact
that, for dipping reflections, the traces of a CMP
gather do not involve a common reflection point.DMO effectively corrects for the reflection-point
smear that results when reflectors dip.
Events with various dips stack with the same velocity
after DMO.
(DMO can be performed in a number of ways)
Sheriff, 1991
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Horizontal Reflector
CMP = CDP
CMP CDP
Dipping Reflector
CMP = common mid pointCDP = common depth point
Dip move out (DMO)
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Loci of reflection points
Zero offset: coincident
Source (S) and geophone (G)
Common offset: offset between
Source (S) and geophone (G)
Show possible reflection points for one particular traveltime
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DMO correction
NMO:coordinate transformation from A (yn,t) to B (yn,tn)DMO:
coordinate transformation from B (yn,tn)to C (y0-t0)Zero-offset migration:
coordinate transformation from C (y0-t0)to D (ym,t)
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Dip Move out (DMO)
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Marine line over a salt structure
Cases of conflicting dip
Analysis of data without DMO correction
Analysis of data with DMO correction
(following pictures are obtained from Yilmaz, 2001)
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Selected CMP gathers from a 2D marine dataset
Yilmaz, 2001
NMO DMO NMO-1
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Velocity spectrum
Without DMO correction
(smearing of data)
With DMO correction
Yilmaz, 2001
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Close-up view of the velocity
spectrum and CMP gather
Without DMO correction
Yilmaz, 2001
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Close-up view of the velocity
spectrum and CMP gather
With DMO correction
Yilmaz, 2001
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Velocity field used to stack the CMP gathers
Without DMO correction With DMO correction
Yilmaz, 2001With DMO: less smearing: more detailed velocity field
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NMO correction of DMO corrected gathers
Without lateral varying and with lateral varying velocityYilmaz 2001
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Field example of DMO correction
NMO
Stacking
Migration
DMO NMO-1 NMO
CMP stack DMO stack
Migrated CMP stack Migrated DMO stack
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CMP stack
and
DMO stack
Yilmaz, 2001
Amplitudes of reflections
off the flanks of the salt
have similar amplitude as
flat events
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Comparison between
Migration of
CMP stack
andDMO stack
Yilmaz, 2001
Amplitudes of reflections
off the flanks of the salt
have higher amplitude
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Time migration of CMP and DMO stack
Yilmaz 2001