Jing Li 12 Sherif Hanafy 1 and Gerard Schuster 1 1 King Abdullah University of Science and Technology KAUST Saudi Arabia 2 Department of Geophysics Jilin University China ID: 779871
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Slide1
Wave Equation Dispersion Inversion of Guided P-Waves (WDG)
Jing Li1,2, Sherif Hanafy1 and Gerard Schuster1
1
King
Abdullah
University
of Science and Technology
(
KAUST), Saudi Arabia
2 Department of Geophysics, Jilin University, China
Slide2MotivationGuided-wave Inversion TheoryResults
Synthetic and Field DataConclusions and Limitation Outline
WDG Tomogram
WDG P-velocity Tomogram
GW
Shot Gather
Slide3Challenge: 1) Inverted accurate velocity model and 2) Statics correctionSolution: W
ave-equation dispersion inversion for Guided-waves (WDG) Motivation
Stack
with static from high resolution velocity
Stack
with static from inaccurate velocity
(Florian
Duret
, et al, 2016, TLE}
Problem:
Traveltime
velocity tomogram has low
resolution and inaccurate
.
Slide4P-wave reverberations
Snapshots of
wavefield
(
Mi
, et al, 2018; LVL
: low velocity layer)
If there is great velocity difference, P-wave will be trapped
in the low velocity
layer (
Grant and
West, 1965)
Shot Gather
Guided-waves
Background for Guided Waves
No Guided waves
Slide5Different kinds of Guided-waves (Boiero, TLE, 2013).
Ocean Bottom Cable (OBC) dataTowed-streamer
Land Seismic data
f
(Hz)
k
(1/m)
f
(Hz)
k
(1/m)
Background for Guided Waves
f
(Hz)
k
(1/m)
Slide6MotivationsGuided-wave Inversion TheoryResults
Synthetic and Field DataConclusions and LimitationOutline
Predicted
Observed
Frequency (Hz)
Dispersion Curves
v (m/s)
Slide71)
Misfit Function Source field
Backpropagated
field
2) Gradient
3) Velocity Update
Guided-wave Inversion Theory
(WDG)
Dispersion Curves
f (Hz)
c (m/s)
Slide8Wave-equation Traveltime Inversion (WT) vs Wave-equation Dispersion Inversion for
Guided-waves (WDG)Wave-equation traveltime tomography (Luo and Schuster, 1991)Wave-equation dispersion tomography (Li and Schuster
,
2018
)
Properties:
Misfit function:
Gradient:
Predicted
Observed
Frequency (Hz)
Wavenumber (m-1)
Frechet
derivative
Slide9Steepest descentInverted Vp
0 x (m) 120 0 10z (m)
WDG
Workflow
True
Vp
Model
0 x (m) 120
0
10z (m)Initial Vp Model
0 x (m) 120
0
10
z (m)
Obs. Dispersion
f (Hz)
v (m/s)
Pred. Dispersion
f (Hz)
v (m/s)
Radon Transform
Residual Dispersion
f (Hz)
k (m-1)
Backpropagated
Data
0 x (m) 120 0 0.5 t (s)WeightedUpdate
0 x (m) 120 0 10z (m)GradientRTMds=ds-alpha*(de\ds)
Slide10MotivationGuided-wave Inversion TheoryResults
Synthetic and Field DataConclusions and LimitationOutline
WDG Tomogram
WDG P-velocity Tomogram
Slide11True P-velocity Model
0
5
10
15
20
0 x (m) 120
z (m)
2500
2000
1500
1000
m/s
WT vs WDG
WT Tomogram
WDG Tomogram
Parameter:
V1=1000 m/s V2=2500 m/s.
f=40 Hz,
λ=25
m
Sr
=30,
Re=60;
Initial P-velocity
Model
λ/2=12.5m
Slide12Synthetic Model TestParameter: V1=1000 m/s V2=2500 m/s.
f=40 Hz, λ=25 m Sr=60, Re=120; 0 10
20
True
P-velocity Model
z (m)
WDG P-velocity
Tomogram
0
10
20
0 60 120 180 240
z (m)
Initial P-velocity
Model
λ/2=12.5m
2500
2000
1500
1000
0
10
20
z (m)
m/s
Slide13Seismic - Parameter
Equipment: Geometrics No of Profiles: 2No. of shots: 120Shot Interval: 5 mNo. of Receivers: 240Receiver Interval: 2.5 mProfile Length: 600
m
Qademah
Field Data Test
(
Sherif
, et al, 2012)
Slide14Radon Transform
Raw Shot Gather
t (s)
x (m)
Adaptive window mute
Dispersion Curves
V (m/s)
f (Hz)
Qademah
Field Data Test
Window
Guided-waves
t (s)
x (m)
Slide15Qademah
Data P-velocity Tomogram 0 40
WT Tomogram
z (m)
3.0
2.2
1.6
1.0
km/s
0
40
z (m)
WDG Tomogram
3.0
2.2
1.6
1.0
km/s
0 600
x (m)
Slide16WDG and WT Common Offset Gather (Offset=40 m)
T (s)
Raw Data COG
0
0.4
WDG Inverted Data COG
0
600
0
0.4
T (s)
Slide17WDG and WT Common Offset Gather (Offset=40 m)
T (s)
Raw Data COG
0
0.4
WT Inverted Data COG
0
600
0
0.4
T (s)
Slide180 0.250 200t (s)
Offset (m)
Raw Data
WT Data
Qademah
Field
CSG Trace
Comparison
Slide190 0.25
0 200
t (s)
Offset (m)
Raw Data
WDG Data
Qademah
Field
CSG Trace
Comparison
Slide20MotivationGuided-wave Inversion TheoryResults
Synthetic and Field DataConclusions and LimitationOutline
Slide21Conclusions1. Guided-waves dispersion inversion (WDG) can accurately reconstruct the
P-velocity in near surface structure. WT
WT Tomogram
Z (m)
x (m)
Dispersion Curve
V (m/s)
f
(Hz)
Radon
Transform
Traveltime
map
Rec.
Source
Pick
WDG
WDG Tomogram
Z (m)
x (m)
Shot Gather
t (s)
x (m)
Shot Gather
t (s)
x (m)
GW
Slide22Conclusions2. WDG tomogram has higher (?) resolution than WT.
WT Tomogram
WDG Tomogram
True P-velocity Model
0
20
0
120
z (m)
x
(m)
2500
2000
1500
1000
m/s
Slide23Limitation
Shot Gather
z (m)
z (m
)
z (m)
V1=1000 m/s
V2=1400 m/s
True
Vp
Model
WDG Tomogram
V1=1000 m/s
V2=2500
m/s
1. WDG not always visible
2. Poor quality dispersion curves
3. Multiscale strategy
Slide24AcknowledgementsSponsors of the CSIM (csim.kaust.edu.sa) consortium.KAUST Supercomputing Laboratory (KSL) and IT research computing group.
Slide25Thank you