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Isochron
(ms twt)
80
N
60
Legend
40
20
Confined channel
Compacted levee
0
0
I
I
ʹ
Unconfined frontal splay
100 m
0
1 km
0
2.5 km
2.5 km
26/4-2
I
ʹ
1850
1900
1950
2000
2050
2100
2150
2200
1850
1900
Sele same time thickness
as shale intervals in well
1950
Top Sele Formation
2000
2050
Top Lista Formation
2100
Top Shetland Gp
2150
2200
0
1 km
Fig. 8.
Transect through channel drilled by well 26/4-2. Shows unmarked and interpreted seismic cross sections with an
explanation of the interpretations and an isochron map at the top. The synthetic seismogram on the un-marked section is
based on a 20 Hz Ricker wavelet. The section is believed to cross a frontal splay overlain by a leveed channel. The discrete
narrow channel (Fig. 3) has a concave upwards base reflector but has not eroded significantly into the Sele Formation
shales that appear to have constant thickness inside and outside the mapped sand fairway. The levees may be dominantly
fine-grained and do not necessarily set up an acoustic impedance contrast to the background sediments and the splay
could be thin and contain linked debrites (see also text and illustration in Fig. 7). Note also that the frontal splays are com-
monly reported in the literature as high amplitude reflector packages (HaRP) and the levees are commonly referred to as
'gull wings' due to their shape in shallow high-frequency datasets. a similar pattern is not seen nor expected to be seen at
2 km depth because: (1) the dominant frequency is lower; (2) the signal-to-noise ratio is lower; (3) the acoustic impedance
contrast between sand and shale is typically lower after differential compaction of sand and shale and (4) the geometry has
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