Spatial and
Temporal Evolution of Densimetric Froude Number in Deep Water Distributive
Systems
Hoyal, David1, Benjamin Sheets1
(1) ExxonMobil Upstream Research Company,
An important control on the performance
of deep-water hydrocarbon reservoirs involves autocyclic structure associated
with the formation, migration and filling of channels. This heterogeneity is
often below seismic resolution, and is commonly modeled statistically based on
reservoir analogs. One reasonable basis for selecting appropriate analogs is an
understanding of the physics underlying channel initiation and evolution.
Dimensional analysis indicates that an important control in all turbulent open
channel flows, including turbidity currents, is the Froude number, which characterizes
important flow properties, as well as important states in flow energetics.
Here we describe detailed laboratory
experiments designed to elucidate the role of the densimetric Froude number
(Fr) in the morphodynamic initiation and evolution of deep water channels in a
distributive setting. In order to optimize for the formation of channels the
experiments decouple the density flow and sediment transport dynamics by using
salt (NaCl) as a densifying agent and crushed plastic as sediment. In particular
we focus on the role of the Fr in determining the length scale of the channel
segments in a distributive system. In addition we quantify, for the first time,
the evolution in Fr associated with the growth of a mouth bar, subsequent
channel bifurcation, channel backfilling and avulsion. Bifurcation over a
channel mouth bar represents a state when the effluent inertia is diminished by
lifting over the bar and is linked to a Fr threshold.
We propose that the Fr has important implications for landscape evolution and
morphodynamic structure in deep-water depositional systems.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California