Detailed
Modeling of Channelized Deposits Using a Process-Based Stochastic Approach
Cojan, Isabelle1, Jacques
Rivoirard1, François Geffroy1 (1) Ecole des Mines de
Paris,
Process-based stochastic models offer the
possibility to represent in a realistic manner the geometries and arrangements
of complex deposits. This is in particular the case of the channelized deposits
associated to meandering systems, whether fluvial or turbiditic.
In the fluvial model, the architecture of
the system is essentially controlled by migration, avulsion and aggradation,
which rule the deposition of the sedimentary bodies and their facies (point
bar, mud plug, overbank deposits, levee/crevasse splay …). These factors
control, in particular, the development and connectivity of point bars. In more
details, the grain size distribution of point bars depends on the sedimentary
load of overbank flows, which can vary in time, and on the vertical sorting.
While the scale is dramatically
different, submarine meandering channels present a marked similarity with the
terrestrial rivers, in particular with regard to their 2D morphology, as was
pointed by many authors. The sedimentary load, however, is the governing factor
of turbidity currents. Based on this, a model of channelized turbiditic
reservoirs is developed, that includes a varying sediment load through time and
space, and a mass balance, taking into account the initial (upstream) grain
size composition of the turbiditic flow and its (more or less depositional or
erosive) nature. Different channelized deposits (lateral accretion package,
coarse channel lag, fine channel fill) can thus be modeled, with individualized
grain size distribution.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California