Moveout-Based Spreading Correction for Mode-Converted Waves

1
Moveout-Based Spreading Correction for
Mode-Converted Waves

• Ellen (Xiaoxia) Ilya

2
Moveout-Based Geometrical Spreading
3
VTI Model
4
Nonhyperbolic Moveout Equations
Tsvankin Thomsen (1994)
Alkhalifah and Tsvankin (1995)
5
Accuracy of MASC with ?-Equation
6
5
Spreading (km)
MASC
4
Ray tracing
3
1
2
Offset/Depth
6
CMP Gather
Offset (km)
0
1
2
3
1.0
Time (s)
PP
2.0
SS
3.0
PS
7
Processing Flow

• pick amplitude
• correct for source and receiver directivity
• correct for geometrical spreading
• calibrate amplitude

8
Comparison of Conversion Coefficients
0.0
MASC
-0.1
Exact
t2-gain
-0.2
0.2
0.0
0.1
0.3
Horizontal slowness (s/km)
9
Transmission Loss
0.15
0.10
0.05
0.00
-0.05
0.1
0.3
0.0
0.2
Horizontal slowness (s/km)
10
Moveout Equation in ORTH Media
11
Orthorhombic Model
ISO
x3
x2
x1
ISO
12
Accuracy of MASC with ?-Equation
6
5
azimuth 90o
Spreading (km)
4
azimuth 0o
3
0
3
2
1
Offset (km)
13
VTI/ORTH Model
VTI
x3
x2
x1
ISO
14
Accuracy of MASC with ?-Equation
6
5
azimuth 90o
Spreading (km)
4
azimuth 0o
3
0
3
2
1
Offset (km)
15
Conclusions

• same algorithm for PP and PSV
• accuracy of ?-equation for PSV lower than for PP
• important for AVO analysis

16
Tilted Transversely Isotropic (TTI) Model
17
Traveltime Surface for TTI layer
Y (km)
X (km)
18
Accuracy of MASC
5
4
MASC
Spreading (km)
3
2
Ray tracing
-1
-2
-3
1
3
2
0
Offset (km)
19
Future Work
Jonah field data application
20
Layered VTI Model
ISO
ISO
ISO
21
(No Transcript)
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Layered ORTH Media (aligned)
23
Layered ORTH Media (misaligned)
24
Generic equation of geometrical spreading
Cervený (2001)