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resolution makes it difficult to compare and con-
trast them to more deeply buried submarine fans.
The present paper was motivated by the excellent
seismic imaging of subtle geometries that are nor-
mally not recognised in deeply buried submarine
fans and it is therefore an example of how
enhanced seismic imaging can strengthen the link
between subsurface systems and their analogues.
Modern submarine fan channels generally have
well developed levees and levees become increas-
ingly recognised as an important constituent of
ancient outcrop successions (e.g. Walker, 1985;
Fergusson
et al
., 1989; di Celma
et al
., 2011), but
they are rarely observable in deeply buried subsur-
face fans. The interpretation of leveed channels,
avulsions and fan-switching sequences herein
suggest a strong autocyclic overprint of the long
term allocyclic patterns of fan initiation, growth
and retreat. Moreover, the suggested close associa-
tion between sand and channels, as opposed to
sand sheets that spread uniformly over large areas,
have important implications for the lateral conti-
nuity of potential hydrocarbon reservoirs.
The possibility of sand being focused primarily
in autocyclically-controlled levee-confined chan-
nels and frontal splays of limited size is an issue
that should be accounted for in the estimation of
petroleum migration, trapping and reservoir per-
formance. Likewise, the erosion at the base of
channels and the possible amalgamation of dis-
crete sand fairways may become important for
estimating the reservoir connectivity between dis-
crete sand fairways. Post-depositional sand remo-
bilisation can also be important for reservoir
prediction as injectites may, in many cases, be the
only connectors between sand fairways. an under-
standing of the relationships between possible
fluid migration routes and connected elements in
a set of deformation structures could be important
for understanding the behaviour of hydrocarbons
in these reservoirs. The recognition of sand-
evacuation structures is also important as such
depressions can indicate patches of non-reservoir
in an otherwise excellent sandstone reservoir.
The basic building blocks of the sand frame-
work are thought to be channels with connected
splays, injectites and steep-sided mounds. Levees
are expected to have high clay-silt content and
may be indistinguishable from the distal run-outs
from low-density turbidity currents in the outer
parts of splays. The avulsion process is thought to
have produced a complex stack of channels and
splays, draped by inter-channel facies. Indications
of incisions related to headward erosion from the
nick-points set up by a structured palaeo sea floor
have also been discussed (channel C4S previously
discussed and Fig. 7). It is considered that such
incisions could have eroded the levees of adjacent
channels and later have evolved from erosional
conduits to depositional channels. This process
has probably promoted lateral communication
between channel-splay pairs.
The observation of a vertical succession of tens
of metres of clean sandstone in both steep-sided
mounds and a leveed channel highlights the
uncertainty associated with predicting sandstone
geometry away from well control. The thick-
bedded sandstones with excellent reservoir qual-
ity display a multifaceted 3d shape which can
only be satisfactorily comprehended by the use of
conditioned 3d seismic data. The findings of this
study reflect the utility of tailored geophysical
workflows and integrated core/well datasets for
the optimal visualisation of sandstone geometries
within the target interval.
CONCLUSIONS
The linkage of seismic geomorphologies to sedi-
mentary facies has enabled the following conclu-
sions to be drawn from this study:
1
The application of a combination of geophysi-
cal techniques applied to 3d seismic datasets
have resulted in the recognition of some mor-
phologies indicative of processes that are well
known from modern submarine fans and out-
crop studies, but rarely observable in deeply
buried ancient fans. These morphologies
include leveed channels, avulsions, braided
frontal splays and pockmarks.
2
The regional dip and overall direction of fan
growth was towards the south-east, largely
controlled by the structural grain of an exten-
sional transfer zone in the segmented Viking
Graben. The fan evolved in a stepwise manner,
interrupted by temporary channel deviations
towards the north-east, following the grain of
the Viking Graben. deviations from the regional
progradation trend suggest transient confine-
ment by subtle, structurally controlled, bathy-
metric features.
3
Evidence for frequent avulsions suggests that
only one part of the outer fan was active at a
given time. Sand deposition occurred in active
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