Preferential Mode of gas invasion in sediments: Grain-scale mechanistic model of coupled multiphase fluid flow and sediment mechanics
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Author(s)
Juanes, Ruben
Jain, A. K.
Date Issued
August 2009
Journal
Journal of Geophysical Research
Publisher
American Geophysical Union
Citation
Jain, A. K., and R. Juanes. “Preferential Mode of gas invasion in sediments: Grain-scale mechanistic model of coupled multiphase fluid flow and sediment mechanics.” J. Geophys. Res. 114.B8 (2009): B08101. ©2009 American Geophysical Union.
Version
Final published version
Abstract
We present a discrete element model for simulating, at the grain scale, gas migration
in brine-saturated deformable media.We rigorously account for the presence of two fluids in
the pore space by incorporating forces on grains due to pore fluid pressures and surface
tension between fluids. This model, which couples multiphase fluid flow with sediment
mechanics, permits investigation of the upward migration of gas through a brine-filled
sediment column. We elucidate the ways in which gas migration may take place: (1) by
capillary invasion in a rigid-like medium and (2) by initiation and propagation of a
fracture. We find that grain size is the main factor controlling the mode of gas transport
in the sediment, and we show that coarse-grain sediments favor capillary invasion,
whereas fracturing dominates in fine-grain media. The results have important
implications for understanding vent sites and pockmarks in the ocean floor, deep subseabed storage of carbon dioxide, and gas hydrate accumulations in ocean sediments
and permafrost regions. Our results predict that in fine sediments, hydrate will likely
form in veins following a fracture network pattern, and the hydrate concentration will
likely be quite low. In coarse sediments, the buoyant methane gas is likely to invade
the pore space more uniformly, in a process akin to invasion percolation, and the
overall pore occupancy is likely to be much higher than for a fracture-dominated
regime. These implications are consistent with laboratory experiments and field
observations of methane hydrates in natural systems.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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DOI of Published Version
https://doi.org/10.1029/2008jb006002
