Basic scheme of the seismic data processing

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Basic scheme of the seismic data processing
Measurements
Loading of the data/conversion
Navigation
Demultiplexing
Pre-Processing
Geometry
Editing
Amplitude correction
Frequency filter
Deconvolution
Prestack
CMP-Sorting
Velocity analysis
NMO/DMO-Correction
Stacking
Migration
Poststack
Post-processing
Printing/storage
Printing/storage
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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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Dip move out (DMO)
Horizontal Reflector
CMP CDP
Dipping Reflector
CMP¹ CDP
CMP common mid point CDP common depth point
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Loci of reflection points
Common offset offset between Source (S) and
geophone (G)
Zero offset coincident 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
NMO
DMO
NMO-1
Yilmaz, 2001
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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
With DMO less smearing more detailed velocity
field
Yilmaz, 2001
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NMO correction of DMO corrected gathers
Without lateral varying and with lateral varying
velocity
Yilmaz, 2001
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Field example of DMO correction
NMO
Stacking
Migration
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CMP stack and DMO stack
Amplitudes of reflections off the flanks of the
salt have similar amplitude as flat events
Yilmaz, 2001
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Comparison between Migration of CMP stack
and DMO stack
Amplitudes of reflections off the flanks of the
salt have higher amplitude
Yilmaz, 2001
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Time migration of CMP and DMO stack
Yilmaz, 2001