seismic reflection 3: acquisiton, processing, and waveform analysis
TRANSCRIPT
Introduction to Geophysics
Ali [email protected].
saDepartment of Earth SciencesKFUPM
Seismic Reflection 3: Acquisiton, Processing, and Waveform Analysis
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Previous Lecture
Example: Data Acquisition in Shaybah Field (Alfaraj et al., 1998, GeoArabia, Vol. 3, No 2)Over 120 million seismic traces and over 100,000 shot points, covering an area of about 1,100 sq km. Primary Reflection Multiples NMO – Normal Moveout Correction Velocity Analysis Example: Gathers and NMO Corrected CMP Mute
Static Corrections
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Average Velocity
( )
j
i ii
average j
ii
V tV j
t
Vav= average velocity above the interface
Z= depth from the surface to the interfacet= one-way travel from surface to interface
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Root Mean Square (RMS) Velocity
1/2
2
1( )
1
j
irms j j
i
V tV
t
VRMS= root mean square velocity
Vi= seismic velocity of the ith layer
ti= two-way travel time within the ith layer
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Interval Velocity (Vint)
122 2
1 1interval
1
n n n n
n n
V t V tV
t t
For n=2V1= Stacking velocity for reflection from upper interface [VRMS(1)]
V2= Stacking velocity for reflection from lower interface [VRMS(2)]
Dix, 1955 (p.130 of Sheriff and Geldart, 1995)
Vint=ΔZ/ Δt
Vint= average velocity between two interfaces
ΔZ= thickness of layer between the two interfacesΔt= one-way travel time between the two interfaces
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
Mid-Term ExamMay 3
Field-Trip April 26, 12.30 PM
Intr
od
uct
ion t
o G
eop
hysi
cs-K
FUPM
12.10 AM- 13.00 AM
We may recover two classes time
1. What does fold mean in the CMP method? Give an example.
2. What are the two advantages of the CMP method over previous methods?
P.C: Open Book
The quiz of the weekIn
trod
uct
ion t
o G
eop
hysi
cs-K
FUPM