Basic Idea

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Basic Idea If I can change the
properties of the free surface, both free surface
multiples and ghosts will be changed. Primaries
will not suffer any changes.
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Experiment 1
Experiment 2
CASP
Sea surface
CASP
Sea surface
Sea floor
Sea floor
Primaries
Primaries Internal multiple
Internal multiple Ghosts
Ghosts Free
surface Free
surface
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Key Question Is this result true and applicable
for all marine acquisition techniques ?
Yes
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VC
Sea surface
CASP
Sea surface
Sea floor
Sea floor
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Walkaway VSP
CASP
Sea surface
CASP
Sea surface
Sea floor
Sea floor
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OBS
CASP
Sea surface
CASP
Sea surface
Sea floor
Sea floor
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How can we end with data free of surface
multiples?
Experiment 2
D2 P M2
Experiment 1 D1 P M1
2P (D2 D1) A(?) (D2 D1)
2P 2P (M2 M1) A(?) (M2 M1)
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How can we take the advantage of this basic idea
in the real live?
By using both 1-Natural Phenomena
- High tide/Low tide.
- SOFAR channel. 2-Artificial
Experiments - Air
bubbles. - Foam plates.
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High Tide/Low Tide
Joy Wagon, Science, 1999.
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(No Transcript)
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400 PM
130 PM
1025 AM
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0600 PM
1100 AM
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SOFAR Channel
What is the SOFAR Channel?
It's a layer of water deep in the ocean where the
speed of sound is at a minimum, and called SOund
Fixing And Ringing.
The SOFAR channel is formed by the interplay
between changes in ocean temperature and pressure.
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http//geosun.sjsu.edu/105d/exped13/18.html
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SOFAR Channel
Sea surface
Sea surface
Sea floor
Sea floor
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• Conclusion
• -Any changes in the physical properties of sea
  surface or near it
• only affect free-surface multiples and ghosts.
• Takings the advantage of such changes, and from
  two acquisitions
• we can end with a seismic data free of surface
  multiples.
• - This fact is true for Streamer, OBS, VC and
  WVSP.
• The repeatability of acquisition geometry play
  the major role in
• the success of this approach.
• We are working in the investigations of any
  possible artificial changes that could be
  applicable in commercial scales.