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Making CMP’s From chapter 16 “Elements of 3D Seismology” by Chris Liner.

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Presentation on theme: "Making CMP’s From chapter 16 “Elements of 3D Seismology” by Chris Liner."— Presentation transcript:

1 Making CMP’s From chapter 16 “Elements of 3D Seismology” by Chris Liner

2 Outline Normal Moveout Stacking

3 Normal Moveout x T Hyperbola:

4 Normal Moveout x T “Overcorrected” Normal Moveout is too large Chosen velocity for NMO is too (a) large (b) small

5 Normal Moveout x T “Overcorrected” Normal Moveout is too large Chosen velocity for NMO is too small (a) large (b) small

6 Normal Moveout x T “Under corrected” Normal Moveout is too small Chosen velocity for NMO is (a) too large (b) too small

7 Normal Moveout x T “Under corrected” Normal Moveout is too small Chosen velocity for NMO is too large (a) too large (b) too small

8 Vinterval from Vrms Dix, 1955

9 Vrms V1 V2 V3 Vrms < Vinterval

10 Vinterval from Vrms

11 Primary seismic events x T

12 x T

13 x T

14 x T

15 Multiples and Primaries x T M1 M2

16 Conventional NMO before stacking x T NMO correction V=V(depth) e.g., V=mz + B M1 M2 “Properly corrected” Normal Moveout is just right Chosen velocity for NMO is correct

17 Over-correction (e.g. 80% Vnmo) x T NMO correction V=V(depth) e.g., V=0.8(mz + B) M1 M2 x T M1 M2

18 f-k filtering before stacking (Ryu) x T NMO correction V=V(depth) e.g., V=0.8(mz + B) M1 M2 x T

19 Correct back to 100% NMO x T NMO correction V=V(depth) e.g., V=(mz + B) M1 M2 x T M1 M2

20 Outline Convolution and Deconvolution Normal Moveout Stacking

21 NMO stretching V1 V2 T0T0 “NMO Stretching”

22 NMO stretching V1V1 V2V2 T0T0 “NMO Stretching” V 1

23 NMO stretching V1V1 V2V2 V 1

24 NMO stretching V1V1 V2V2 V 1

25 stretching for T=2s,V1=V2=1500 m/s Green line assumes V1=V2 Blue line is for general case, where V1, V2 can be different and delT0=0.1s (this case: V1=V2) Matlab code

26 Stacking + + =

27 + + = Stacking improves S/N ratio

28 + = Semblance Analysis “Semblance” + X Twtt (s)

29 + = Semblance Analysis + X Twtt (s) V3V3 V1V1 V2V2 V Peak energy


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