1 / 22

Modeling of free-surface multiples

Modeling of free-surface multiples. Using the data as modeling operator: Tutorial Case study example Discussion. sea surface. = receiver. = shot. reflector. D( ) = P ( ) + D ( ) ( r W( ) -1 )P ( ).  : frequency D = Data

caine
Download Presentation

Modeling of free-surface multiples

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Modeling of free-surface multiples • Using the data as modeling operator: • Tutorial • Case study example • Discussion

  2. sea surface = receiver = shot reflector

  3. D() = P () + D ()( r W()-1 )P () •  :frequency • D = Data • P = Primaries (data in experiment without free surface) • W = Acquisition wavelet • r = Reflection coefficient at free surface

  4. = receiver = shot sea surface reflector

  5. D() = P () + D ()( r W()-1 )P () Pi(,s,g) = D (,s,g) - ( r W()-1 ) Sx D(, s,x)P i-1(,x,g) x1 x2

  6. Prepare two-sided shot gathers at locations S and G interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Model of free-surface multiples at location SG

  7. Prepare two-sided shot gathers at locations G andS interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Model of free-surface multiples at trace GS

  8. Prepare two-sided shot gathers at locations G andS interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Convolve the two-sided shot gathers trace by trace Model of free-surface multiples at trace GS

  9. Prepare two-sided shot gathers at locations G andS interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Convolve the two-sided shot gathers trace by trace Model of free-surface multiples at trace GS

  10. Prepare two-sided shot gathers at locations G andS interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Convolve the two-sided shot gathers trace by trace here convolution in x-t other options after transforms time to frequency offset to ray-parameter offset to wavenumber Model of free-surface multiples at trace GS

  11. Prepare two-sided shot gathers at locations G andS interpolate gaps use reciprocal traces from common receiver gathers at locations S and G Convolve the two-sided shot gathers trace by trace Apply tapers, mutes, interpolation, etc Sum traces to obtain the multiple model trace Model of free-surface multiples at trace GS

  12. Repeat the previous procedure for all traces in the shot gather Model of free-surface multiples for shot gathers at location S

  13. Case study example – 2-D, East of Faroes Islands • Acquisition (1999): • Single vessel, towing 11.4 km long streamer • Shot interval 25 m • Group interval 12.5 m • 10 sec records • Grid of eleven 2-D lines • One 120 km long line available at SEP

  14. is an issue for SRME Source locations 3 km Receiver locations Feathering

  15. East of Faroe Islands (ten 2-D lines, 1700 km total)

  16. 12 km Pre-stack time migration

  17. LMO 4 km/sec Input Model Output SRME applied to data from the 1999 survey(offsets up to 9 km)

  18. WBM TBM TB WBM WBM SRME in Shot Gather Domain WB TB TBM WBM TBM Input Input-Predicted multiples Predicted multiples

  19. Requirement for sources and receivers at the same locations … • Heuristics: • Don’t convolve traces which are ``too far apart’’ • Bandpass and dip-filter traces as function of their distance • Estimate ``plane-wave components” from the data and use these to compute the multiple model • Sx D(, s,x)P(,x,g)~Sp D(, s,p)P(,p,g) • x : space coordinate • p : spatial wavenumber or ray-parameter (ps or pg)

  20. Gathers as function of offset (left) and ray-parameter (right)

  21. Models before summation along offsets (left) andray-parameter (right)

  22. Further work • Effect of position errors (non-coincident sources and receivers) on synthetics: • Use source and receiver positions from the field data; • Specifications for maximum feathering during acquisition • Display/Filter intermediate results when computing the multiple model • Investigate computing the multiple model by convolving plane wave components • Local plane-wave decompositions within CRG/CSG gathers? • Could handle also interpolation of missing near-offsets?

More Related