Post on 05-Feb-2016
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Processing and Binning Overview
From chapter 14 “Elements of 3D Seismology” by Chris Liner
Outline
•Justification for Processing
•Processing Flow
•Bins
Justification
Field data representation of the data is distant from a distance-depth representation of data.
Categories of Processing
Adjustments to wavelets, or short-pulse adjustments e.g.,
•frequency filtering
•phase shifts (rotation)
•vibroseis correlationTraveltime Corrections (fig. 14.1) :
Statics
Normal Moveout
Dip Moveout
Migration
Categories of Processing
•Amplitude Corrections
• Geometric spreading
•Automatic Gain Control
•Noise Reduction
•Vertical stack
•Muting
•CMP stack
•filtering (f, f-k, tau-p (or radon)
•multiple suppression
Xia et al., 2004
An example of analysis for near-surface seismic structure
Seismic data “Multiple universes for seismic data”
•Shotpoint gathers (distance versus time)
•CMP gathers (distance versus time)
•Tau-p (horizontal slowness versus intercept time)
•f-k (frequency versus wavenumber)
Distance between shot and the receiver (m)
Tw
o-w
ay t
ravelt
ime
(s)
Distance between shot and the receiver (m)
Tw
o-w
ay t
ravelt
ime
(s)
dT/dx = 1/V (s/m)
Velocity (m/s)
T2 = T02 + x2/ V2
T0
Distance between shot and the receiver (m)
Tw
o-w
ay t
ravelt
ime
(s)
dT/dx = 1/V (s/m)
Velocity (m/s)
T2 = T02 + x2/ V2
T0
dT/dx = 1/V (s/m)
x
1/V = 0 ( s/m)
1/V = p (ray parameter)
V
Distance between shot and the receiver (m)
Tw
o-w
ay t
ravelt
ime
(s)
dT/dx = 1/V (s/m)
Velocity (m/s)
T2 = T02 + x2/ V2
T0
dT/dx = 1/Vh (s/m)
x
1/Vh = 1/[V/ sin(angle) ] ( s/m)
1/Vh = p (ray parameter)
angleV
Distance between shot and the receiver (m)
Tw
o-w
ay t
ravelt
ime
(s)
dT/dx = 1/V (s/m)
Velocity (m/s)
T2 = T02 + x2/ V2
T0
x
1/Vh = 1/[V/sin(angle) ]( s/m)
1/Vh = p (ray parameter)
angleV
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
T0
p (s/m)
p=0
tau (
inte
rcept
tim
e)
s
Add amplitude
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
T0
p (s/m)
p=0
tau (
inte
rcept
tim
e)
s
Add amplitude
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
f (1/s)
p=0
k (w
avenu
mber
- 1
/m)
V=f/k (m/s)
100 Hz
1000 m/s
1/10 m
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
f (1/s)
p=0
k (w
avenu
mber
- 1
/m)
V=f/k (m/s)
100 Hz
1000 m/s
1/10 m
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
f (1/s)
k (w
avenu
mber
- 1
/m)
Vh=inf (m/s)
Vh =1000 (m
/s)
Vh=inf (m/s)
V h=10
00 (m
/s)
P-wave
& Sv -wave
Sz
Sx
“skin depth” = 1/2 longest wavelength
Vh ~= 90% shear wave velocity
Dispersion
t0 t1 t2
t1 t2
Dispersion
Xia et al., 2004
x (m)
Tw
o-w
ay t
ravelt
ime
(s)
f (1/s)
p=0
k (w
avenu
mber
- 1
/m)
V=f/k (m/s)
100 Hz
1000 m/s
Outline
Bins
Calculated common midpoints
“CMP bin center”
Length and width of bin <= spatial aliasing dimensions
To prevent aliasing:
max dimension = V/4fmax
For GOM:
V = V0 + 0.4 x depth
Rule of Thumb: 12.5m by 12.5 m for > 2000 m
IDEAL BIN SIZE: 5m by 5m for seafloor and deeper
The “best” bin:
•SMALL
•ALL OFFSETS
•ALL AZIMUTHS
•LARGE FOLD
Outline
•Justification for Processing
•Processing Flow
•Bins