Passive advection-dispersion in networks of pipes: Effect of connectivity and relationship to permeability

TitlePassive advection-dispersion in networks of pipes: Effect of connectivity and relationship to permeability
Publication TypeJournal Article
Year of Publication2016
AuthorsBernabe, Y, Wang, Y, Qi, T, Li, M
JournalJournal of Geophysical Research: Solid Earth
Volume121
Issue2
Pagination713 - 728
Date PublishedJan-02-2016
Abstract

The main purpose of this work is to investigate the relationship between passive advection-dispersion
and permeability in porous materials presumed to be statistically homogeneous at scales larger than the pore
scale but smaller than the reservoir scale. We simulated fluid flow through pipe network realizations with different
pipe radius distributions and different levels of connectivity. The flow simulations used periodic boundary
conditions, allowing monitoring of the advective motion of solute particles in a large periodic array of identical
network realizations. In order to simulate dispersion, we assumed that the solute particles obeyed Taylor dispersion
in individual pipes. When a particle entered a pipe, a residence time consistent with local Taylor dispersion was
randomly assigned to it. When exiting the pipe, the particle randomly proceeded into one of the pipes connected
to the original one according to probabilities proportional to the outgoing volumetric flow in each pipe. For
each simulation we tracked the motion of at least 6000 solute particles. The mean fluid velocity was 103ms1,
and the distance traveled was on the order of 10 m. Macroscopic dispersion was quantified using the method of
moments. Despite differences arising from using different types of lattices (simple cubic, body-centered cubic,
and face-centered cubic), a number of general observations were made. Longitudinal dispersion was at least 1
order of magnitude greater than transverse dispersion, and both strongly increased with decreasing pore
connectivity and/or pore size variability. In conditions of variable hydraulic radius and fixed pore connectivity and
pore size variability, the simulated dispersivities increased as power laws of the hydraulic radius and, consequently,
of permeability, in agreement with previously published experimental results. Based on these observations, we
were able to resolve some of the complexity of the relationship between dispersivity and permeability.

URLhttp://doi.wiley.com/10.1002/jgrb.v121.2http://doi.wiley.com/10.1002/2015JB012487http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JB012487http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.1002%2F2015JB012487
DOI10.1002/jgrb.v121.210.1002/2015JB012487
Short TitleJ. Geophys. Res. Solid Earth