HR: 0830h
AN: H31D-0494    [PDF]
TI: Pore-Scale Numerical Investigations of 2-Phase Displacement Including Buoyancy forces
AU: * Benito, P H
EM: pbenito@uclink4.berkeley.edu
AF: Department of Civil and Environmental Engineering University of California at Berkeley, 440 Davis Hall U.C.Berkeley, Berkeley, CA 94720 United States
AU: * Benito, P H
EM: pbenito@uclink4.berkeley.edu
AF: Earth Sciences Division. Lawrence Berkeley National Lab, 1 Cyclotron Road, Mail Stop 90-1116, Berkeley, CA 94720 United States
AU: Patzek, T W
EM: patzek@patzek.berkeley.edu
AF: Department of Civil and Environmental Engineering University of California at Berkeley, 440 Davis Hall U.C.Berkeley, Berkeley, CA 94720 United States
AU: Patzek, T W
EM: patzek@patzek.berkeley.edu
AF: Earth Sciences Division. Lawrence Berkeley National Lab, 1 Cyclotron Road, Mail Stop 90-1116, Berkeley, CA 94720 United States
AB: Understanding the behavior and geometry of multi-phase immiscible displacement fronts is critical in the fields of environmental restoration, geologic hazardous waste storage, and petroleum engineering ({\it e.g.} air sparging, NAPL infiltration, and secondary recovery of petroleum by water flooding). Depending on the flow conditions, the presence of gradients, such as those caused by gravity forces, viscous forces or permeability gradients, can variously lead to either stabilized ({\it e.g.} piston-like) or to unstable ({\it e.g.} gravity or viscous fingering) displacement fronts. Previous studies have found that the resulting displacement frontsmay have patterns with percolation, or fractal, characteristics which cannot be adequately described by continuum equations [Chaouche {\it et al.}, 1994; Glass \& Yarrington, 1996; and, Zhang {\it et al.}, 2000]. Numerical pore-network models which incorporate the appropriate physics provide a framework in which to study these characteristics of flow in porous materials. We present results of numerical simulations on regular two- and three-dimensional lattices which are based on the method of invasion percolation in a gradient (IPG). The pore-network is populated with pore throats and bodies whose radii are drawn from a random statistical distribution. The network is initially water saturated and then invaded by a non-wetting fluid (drainage). Both capillary and buoyancy forces are included to define a filling potential for each pore. The invasion advances in quasi-static steps, by increasing the capillary pressure and invading accessible pores with the lowest filling potential at each step. The wetting phase can become trapped in pores that become isolated from the outlet face. We identify the regimes in which stable and unstable displacement occurs and we examine how the fractal geometry of the displacement front and the relative permeability of each phase varies with the Bond Number (the ratio of characteristic buoyancy and capillary forces). We also confirm the power-law scaling of the front width with the Bond Number as derived from percolation theory
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting