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By
Julian D. Clark1, Andrea Fildani1, and Nicholas J. Drinkwater2
Search and Discovery Article #50094 (2008)
Posted October 22, 2008
*Adapted from oral presentation at AAPG Annual Convention,
1Energy Technology Co., Chevron,
2Energy
Technology Co., Chevron,
Deepwater channel outcrops in the dewatering
and flame structures. Towards the
margin these facies change laterally to thinner inter-bedded graded sandstones.
These observations imply that numerous relatively high velocity turbidity
currents were responsible for cutting the channels, with the majority of the
sediment load bypassing down slope. Increases in flow velocity can either be
related to changes in the staging area of the flows, or an increase in the
channel floor gradient as channels attempt to establish equilibrium gradients on
an irregular or dynamic slope. Seismic data from analogous subsurface systems
suggests that the latter is a very common process in controlling channel
architecture. In many channels, after the initial bypass phase, flows with a
lower velocity backfill the channel resulting in rapid sand deposition. Debris
flow deposits within channels are considered to be random events, but their
common association with bypass facies may be related to the longevity of the
bypass phase relative to the backfilling phase. Processes of bypass and
backfilling operate at different scales, magnitudes and frequencies, resulting
in a hierarchy of channelized stratigraphy with predictable facies associations.
Generic models deriving from this work can be used to aid interpretation and
modeling of analogous reservoirs.
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Bypass Facies and Processes
“Muddy Channel� interpreted to be complex-scale bypass facies
association:
Debrites can be associated with bypass facies but not the process:
Stratigraphic Controls
Large scale erosional surfaces initiate channel complexes.
But what controls bypass?
Supporting evidence:
Clark, J.D., 1994, Architecture and processes in modern and
ancient deep-marine channel complexes: PhD dissertation,
Falivene, O., A. Pau, A. Gardiner, G. Pickup, et al., 2006, Best
practice stochastic facies modeling from a channel-fill
turbidite sandstone analog (the Quarry outcrop,
Marzo, M., J.A. Munoz, J. Verges, M. Lopez-Blanco, et al., 1998,
Sedimentation and tectonics; case studies from Paleogene,
continental to deep water sequences of the South Pyrenean
foreland basin (NE Spain): 15th International
Congress of Sedimentology (IAS) Field Trip Guidebook, p.
199-204.
Mutti, E., M. Segurét, and M. Sgavetti, 1989, Sedimentation and
deformation in the Tertiary sequences of the southern
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