HR: 1340h
AN: MR13A-0987 [Abstracts]
TI: Porous Compaction in Transient Creep Regime and Implications for Melt and Petroleum Extraction
AU: * Chauveau, B
EM: chauveau@ipgp.jussieu.fr
AF: Equipe de dynamique des fluides geologiques, IPGP., 4 place Jussieu, Paris, 75005,
France
AU: Kaminski, E
EM: kaminski@ipgp.jussieu.fr
AF: Equipe de dynamique des fluides geologiques, IPGP., 4 place Jussieu, Paris, 75005,
France
AB:
Liquid segregation through a porous medium depends on the ability of the matrix to deform and compact.
The key question of the rheological behavior of the porous matrix has been mainly investigated for Newtonian and
simple visco-elastic
Maxwell-like rheologies. Earth's materials have a more complex rheological behavior, in which the balance
between the elastic and viscous
contribution to the deformation is time-dependent.
In this paper, we propose a Burger-type model to investigate the implications of transient rheology for viscous
compaction
of a porous material. The model is characterized by three dimensionless parameters: (1) the Deborah number,
De, defined
as the ratio of an elastic time scale over the compaction time scale, (2)
the ratio of the transient and steady viscosities, λμ,
and (3) the ratio of the transient and steady rigidity moduli,
λG. We perform 1-D numerical experiments to illustrate the general
behavior of compaction in a transient creep regime as a function
of the model parameters.
For small De (De< 10-2) the compaction occurs in the classical viscous mode and solitary waves
(magmons) are generated. For larger De, the compaction mechanism
is mainly controlled by λμ. For small transient viscosity (λμ → 0), compaction
occurs in an elastic mode and shock waves are generated. For increasing λμ, two new regimes are
observed, first "shaggy" shock waves and then "polytons". The threshold value of λμ
that defines the two regimes is a decreasing function of De. Shaggy shock waves are characterized by the
presence of secondary peaks at the wave propagation front.
The length-scale of the peaks is a decreasing function of λG and their amplitude decreases along the
propagation. In the polytons regime,
the peaks tend to detach and mimic the behavior of solitary waves.
Based on a discussion of the likely values of the model parameters
for the Earth, we conclude that the influence of transient creep should not
be neglected. Polytons and shaggy shock waves are expected both in the mantle
and in sedimentary basins.
Polytons will require a particular attention as they
imply larger extraction velocities and smaller compaction length-scales than the usual magmons.
DE: 3621 Mantle processes (1038)
DE: 4455 Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, 7852)
DE: 5120 Plasticity, diffusion, and creep
DE: 8434 Magma migration and fragmentation
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting