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a)
(b)
(c)
(d)
(e)
Apparent
thickness
Average band-limited
impedance
Seismic
net-to-gross
Net pay
Figure 10.17 A West Africa example of net pay estimation; (a) far-stack coloured inversion, (b) apparent thickness, (c) average bandlimited
impedance, (d) seismic N:G and (e) net pay (after Connolly, 2007 ).
a)
1100
1200
1300
b)
c)
d)
-3000
-30000
300
-20000
200
-2000
-1000
-10000
100
0
0
0
0
20
40
60
80
0
20
40
60
80
-10000
-6000
-2000
0
Apparent thickness (ms)
Apparent thickness (ms)
SNA
Figure 10.18
95 Hz bandpass wavelet, (b) typical tuning curve
generated from average bandlimited impedance, (c) tuning curve for sum of negative amplitudes (SNA), (d) relationship between SNA and
actual sand thickness. Red numbers ΒΌ net sand in feet.
Low-impedance wedge model; (a) bandlimited impedance using 4
-
14
-
75
-
thickness/amplitude classes and use the model data
for quantitative estimation of uncertainty.
With respect to Connolly
increase in amplitude but a decrease in apparent
thickness, contrary to a simple tuning model.
Many pseudo-wells can be used to populate appar-
ent thickness vs seismic amplitude space providing a
template for interpretation. Fervari and Luoni ( 2006 )
have used this technique to generate a net pay tem-
plate for a turbidite reservoir ( Fig. 10.20 ). It should be
noted that the net pay lines shown in Fig. 10.20 are
effectively averages (i.e. there is significant overlap of
net pay solutions). Thus,
s net pay estimation
technique, Connolly and Kemper ( 2007 ) and Con-
nolly ( 2010 ) address the problem of uncertainty in
terms of pseudo-wells. The workflow (shown in Fig.
10.21 ) comprises the following steps.
'
Determine layer configuration of sands and shales
for a given reservoir interval (Connolly and
Kemper ( 2007 ) use a fractal model conditioned by
the well data).
it would be relatively
235
straightforward to split
the plot up into various
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