Geoscience Reference
In-Depth Information
Bulk density (g/cm 3 )
2.8
1.8
2.0
2.2
2.4
2.6
3.0
4.5
30 000
4.4
Dolomite
25 000
4.3
20 000
Limestone
4.2
Rock salt
15 000
Anhydrite
4.1
12 000
Time-average
(Sandstone)
4.0
10 000
Sandstone
8000
3.9
7000
3.8
6000
Shale
=0.23V 0.25
ρ
3.7
5000
3.6 0.2
0.5 3980
0.3
0.4
Logarithm of bulk density (g/cm 3 )
Fig. 5.1
Density vs compressional velocity, redrawn with permission from Gardner et al . (1974) .
The Zoeppritz equations are rather complicated. It is easy enough to write software
to generate curves like those shown in fig. 5.3 , but it is also helpful to have approxima-
tions that give more insight into the underlying relations between reflectivity and rock
properties. Useful approximations for the PP reflection coefficient (i.e. both incident
and reflected waves of P type, the most common situation) have been given by Aki &
Richards (1980) and by Shuey (1985) . Approximately,
B sin 2
C sin 2
tan 2
R (
θ
)
=
A
+
θ +
θ
θ
where
5 V p
V p + ρ
A
=
0
.
ρ
2 V s
V p
2 2 V s
5 V p
V s + ρ
B
=
0
.
V p −
ρ
 
Previous Page
Next Page
3-D Seismic Interpretation
Search WWH ::




Custom Search
Home