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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Geological Architecture and Reservoir Characteristics
of Fine-Grained and Coarse-Grained Turbidite Systems
By
Louisiana State University,
Baton Rouge, Louisiana
Exploration and production of oil and gas from deepwater turbidite systems is of high interest to most companies. Several models have been developed, emphasizing the architecture and several aspects of reservoir characterization. Application of a non-suitable model can result in dry holes, bypassed oil, and other frustrations. Of all general models available the most important ones are the coarse-grained and the fine-grained turbidite systems.
The coarse-grained systems are canyon-fed prograding fans that
gradually become thinner and finer in the down-dip direction.
The fine-grained systems are delta-fed bypassing fan types
with
well
developed leveed channels and significant depositional lobes
or sheet sands on the outer/lower fan. Calculations on the
Mississippi Fan and Tanqua Karoo fans in South Africa indicate
that 75% or more of all the sand in he-grained fans is stored in
the sheet sands. Just to indicate that coarse-grained turbidite systems
are related to active margins and fine-grained ones to passive
margins is only partially correct. The terms active and passive
margins should not be used to identify turbidite system
types
.
A general understanding of the types
of transport and depositional
processes responsible for the distribution and
characteristics of the sands and shales is essential. The factors
(tectonics, climate, sediment, relative sea level fluctuations) that
influence basin setting, transport, deposition and timing interact
rather variably with one and another.
The coarse-grained turbidite systems are rather well
understood
because those deposits are common in outcrop, often adjacent to
productive fields. Fine-grained turbidite systems commonly do
not outcrop. That makes it very difficult to determine
architectural changes in downdip and lateral direction, as
well
as
reservoir continuity. The non-tilted Permian Tanqua Karoo fan
systems in South Africa are the only ones known to make it
possible to conduct such observations.
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