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Jing Wu* and Arthur B. Weglein M-‐OSRP, University of Houston
October 19, 2015
PREPROCESSING IN DISPLACEMENT SPACE IN PREPARATION FOR ONSHORE SEISMIC PROCESSING: REMOVING GROUND ROLL AND GHOSTS WITHOUT
DAMAGING THE REFLECTION DATA
MOTIVATION
• Preprocessing ü is required for all land seismic data processing
2
Boustani et al., 13
3
Boustani et al., 13
4
Ground roll (Rayleigh wave)
Boustani et al., 13
5
Ground roll (Rayleigh wave)
Direct wave
Boustani et al., 13
6
Ground roll (Rayleigh wave)
Direct wave
Ghosts exist in reflec^on
Boustani et al., 13
Ground roll (Rayleigh wave)
7
Ghosts exist in reflec^on
Preprocessing to separate these events from upgoing reflec^on
Direct wave
MOTIVATION
• Preprocessing ü is required for all land seismic data processing
ü provides necessary prerequisite for Inverse Sca`ering Series (ISS) mul^ple removal, which is the most capable method available today and does not need any subsurface informa^on
8
IMPACT OF DEGHOSTING ON ISS MULTIPLE REMOVAL
9 ( Jinlong Yang, 14; P. Carvalho and A. Weglein, 92; Jingfeng Zhang, 05, 06, 07 )
IMPACT OF DEGHOSTING ON ISS MULTIPLE REMOVAL
10
0.5
1.0
1.5
2.0
Tim
e(s)
500 1000 1500Trace Number
Input data with ghosts
Primary + Ghost
Mul^ple + Ghost
0.5
1.0
1.5
2.0
Tim
e(s)
500 1000 1500Trace Number
Mul^ple removal result
Primary + Ghost
Residual
( Jinlong Yang, 14; P. Carvalho and A. Weglein, 92; Jingfeng Zhang, 05, 06, 07 )
IMPACT OF DEGHOSTING ON ISS MULTIPLE REMOVAL
11
0.5
1.0
1.5
2.0
Tim
e(s)
500 1000 1500Trace Number
Input data without ghosts
Primary + Ghost
Mul^ple + Ghost
0.5
1.0
1.5
2.0
Tim
e(s)
500 1000 1500Trace Number
Mul^ple removal result
Primary + Ghost
( Jinlong Yang, 14; P. Carvalho and A. Weglein, 92; Jingfeng Zhang, 05, 06, 07 )
DELIVERABLE OF THIS TALK
• For onshore seismic processing, with the energy source above the
measurement surface, elas^c Green’s theorem can arrange to
remove all direct waves, the receiver ghosts and the ground roll at
once.
12
OUTLINE
Ø THEORY
Ø NUMERICAL TESTS
Ø DISCUSSION AND SUMMARY
13
THEORY
14
GREEN’S THEOREM WAVE SEPARATION
Reference medium
S1
S2
P1
P2
P = P1 + P2
15
GREEN’S THEOREM WAVE SEPARATION
Reference medium
S1
S2
P1
P1 = (P∇ 'G0 −G0∇ 'P) ⋅ n̂ dS '∫
P = P1 + P2
S’ 16
( A. Weglein and B. Secrest, 90; A. Weglein, 02; J. Zhang, 05, 06, 07; J. Mayhan, 12, 13; L. Tang, 13 )
ONSHORE: 2D EXPERIMENT
F. S.
Air
Earth
(ux ,uz )(Fx ,Fz )Source Receiver
17
ONSHORE: 2D EXPERIMENT
M. S. F. S.
Air
Earth
(ux ,uz )
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(Fx ,Fz )
ONSHORE: REFERENCE MEDIUM
M. S. F. S.
Elas/c
19
ONSHORE: REFERENCE MEDIUM + 3 SOURCES + RECEIVERS
M. S. F. S.
Air
Earth
S1
S3
S2
20
(Fx ,Fz )
ONSHORE: REFERENCE MEDIUM
M. S. F. S.
Elas/c
21
M. S. F. S.
Air S2 S1 (Fx ,Fz )
ONSHORE: REFERENCE MEDIUM + SOURCES
22
ü S1 + S2 generate direct wave
Elas/c
M. S. F. S.
Air S2 S1 (Fx ,Fz )
ONSHORE: REFERENCE MEDIUM + SOURCES
23
ü S1 + S2 generate ground roll
Elas/c
ONSHORE: REFERENCE MEDIUM + SOURCES
24
M. S. F. S.
Air S2
ü S1 + S2 generate ghosts
S1 (Fx ,Fz )
Elas/c
ONSHORE: REFERENCE MEDIUM + SOURCES
25
M. S. F. S.
ü S3 generates up reflec/ons
Elas/c Earth
S3
ONSHORE: REFERENCE MEDIUM + 3 SOURCES + RECEIVERS
M. S. F. S.
Air
Earth
S1
S3
S2
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(Fx ,Fz )
ONSHORE: OBTAIN UP WAVE WHEN IS ABOVE M.S. !r
M. S. F. S.
Air
Earth
S1
S3
S2 !r
27
(Fx ,Fz )
ONSHORE: UP WAVE PREDICTION
!uup (!r , !rs ,ω ) = −!t (!r ', !rs ,ω ) ⋅G0 (
!r ', !r ,ω ) − !u(!r ', !rs ,ω ) ⋅ n̂ '⋅ Σ0 (!r ', !r ,ω )( )( ) ⋅dS
m.s.∫
( Weglein and Secrest, 1990 )
!t = ( tx tz ) Traction along the m.s.
!u = ( ux uz ) Total wave
2D:
28 !uup = ( ux
up uzup )
Stress tensor of Green’s function
G0 Green’s tensor in reference medium
Σ0
Up wave
ONSHORE: UP WAVE PREDICTION
!uup (!r , !rs ,ω ) = −!t (!r ', !rs ,ω ) ⋅G0 (
!r ', !r ,ω ) − !u(!r ', !rs ,ω ) ⋅ n̂ '⋅ Σ0 (!r ', !r ,ω )( )( ) ⋅dS
m.s.∫
( Weglein and Secrest, 1990 )
!t = ( tx tz ) Traction along the m.s.
!u = ( ux uz )
2D:
29 !uup = ( ux
up uzup )
ü Direc^onal deriva^ve of displacement is required to compute trac^on
ü Triangle rela^onship among wavelet, displacement and trac^on can be used to determine trac^on ( A. Weglein & L. Amundsen, 2002 )
Total wave
Up wave
ONSHORE: UP WAVE PREDICTION
!uup (!r , !rs ,ω ) = −!t (!r ', !rs ,ω ) ⋅G0 (
!r ', !r ,ω ) − !u(!r ', !rs ,ω ) ⋅ n̂ '⋅ Σ0 (!r ', !r ,ω )( )( ) ⋅dS
m.s.∫
( Weglein and Secrest, 1990 )
!t = ( tx tz ) Traction along the m.s.
!u = ( ux uz )
2D:
30 !uup = ( ux
up uzup )
Stress tensor of Green’s function
G0 Green’s tensor in reference medium
Σ0
Total wave
Up wave
NUMERICAL TESTS ü Onshore shot record with buried receivers ü Onshore shot record with on-‐surface receivers
31
ONSHORE MODEL WITH BURIED RECEIVERS
Layer P Velocity (m/s) S Velocity (m/s) Density (kg/m3)
1 1800 1200 1500 2 4000 2500 1800
F. S. 0m
400m Earth
M.S. 100 m !r(ux ,uz )
32
(0,Fz )
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
33
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Depth of receivers at 100 m
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
34
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Direct Direct
Depth of receivers at 100 m
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
35
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Rayleigh Rayleigh
Depth of receivers at 100 m
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
36
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Up Up
Depth of receivers at 100 m
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
37
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Ghosts Ghosts
Depth of receivers at 100 m
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
38
ux
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Direct Rayleigh
Up
Depth of receivers at 100 m
Ghosts
SEPARATED X COMPONENT OF UP WAVE
39
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Depth of receivers at 100 m
Up
ANALYTIC X COMPONENT OF UP WAVE
40
0
1Time/s
-2000 0 2000Offset/m
-5
0
5
x10 -12
Up
Depth of receivers at 100 m
0 10 20 30 40 50Frequency/Hz
-20
-10
0Am
plitude/DB
SPECTRUM COMPARISON
41
Total wave Separated up wave Analy^c up wave
ONSHORE MODEL WITH ON-‐SURFACE RECEIVERS
F. S. 0m M.S. 0 m !r
400m Earth
(ux ,uz )
42
Layer P Velocity (m/s) S Velocity (m/s) Density (kg/m3)
1 1800 1200 1500 2 4000 2500 1800
(0,Fz )
TOTAL WAVE INPUT TO SEPARATION ALGORITHM
43
ux
Depth of receivers at 0 m
0
1
2
Time/s
-2000 0 2000Offset/m
-1
0
1
x10 -11
Rayleigh
Up + Ghosts
SEPARATED X COMPONENT OF UP WAVE
44 Depth of receivers at 0 m
0
1
2
Time/s
-2000 0 2000Offset/m
-1
0
1
x10 -11
Up
ANALYTIC X COMPONENT OF UP WAVE
45
0
1
2
Time/s
-2000 0 2000Offset/m
-1
0
1
x10 -11
Depth of receivers at 0 m
Up
DISCUSSION AND SUMMARY
46
FOR DIFFERENT ONSHORE WAVE SEPARATION OBJECTIVES
ü If obtaining the upgoing reflec^on is the only interest, elas^c Green’s theorem can remove both ground roll and ghosts at once;
ü If separated ground roll / ghosts are useful for other applica^ons, elas^c Green’s theorem can provide them separately. • A companion talk in SPNA-‐EP: Coherent Noise Removal, room229, Wednesday, 10/21/2015 10:00 AM
47
SUMMARY
Ø Elas^c Green’s theorem in the displacement space can
ü remove ground roll, without damaging reflec^on data;
ü remove ghosts from reflec^on data;
ü provide effec^ve prepara^on for all onshore seismic processing;
ü provide a necessary prerequisite for onshore ISS mul^ple elimina^on.
48
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