HR: 09:00h
AN: H11J-05    [Abstracts]
TI: The effect of residual trapping and slope on gravity currents in confined aquifers
AU: * Hesse, M A
EM: mhesse@stanford.edu
AF: Department of Energy Resources Engineering, 367 Panama Street Green Earth Sciences 065 Stanford University, Stanford, CA 94305-2220,
AU: Tchelepy, H A
EM: tchelepi@stanford.edu
AF: Department of Energy Resources Engineering, 367 Panama Street Green Earth Sciences 065 Stanford University, Stanford, CA 94305-2220,
AU: Orr, F M
EM: fmorr@pangea.stanford.edu
AF: Department of Energy Resources Engineering, 367 Panama Street Green Earth Sciences 065 Stanford University, Stanford, CA 94305-2220,
AB: Motivated by geological CO₂ storage, we present a sharp-interface vertical equilibrium model for the migration of immiscible gravity currents with constant residual trapping in a two-dimensional, sloping, confined aquifer. The continuous loss of residual saturation decreases the current volume over time until the current is exhausted, giving rise to a maximum migration distance and time. Analytic and semi-analytic solutions for the limiting hyperbolic problem are derived. Comparison with numerical solutions show that the limiting solutions are good approximations to the numerical solution for high mobility ratios, M>10, even for Peclet numbers of order unity. For high mobility currents, such as CO₂ in an aquifer our analysis shows that the dimension less migration time and distance increase with increasing mobility ratio and decrease with increasing trapped saturation, but they are only a weak function of the slope as long as the slope is finite. In these cases of finite slope the current evolution is divided into two stages, an initial stage of power-law decrease of volume and a later stage when the volume decays very rapidly. This behavior contrasts strongly with the power-law volume evolution of currents in horizontal aquifers. Several large regional saline aquifers are gently sloping, but lack a structural closure. Our results suggest that the efficient residual trapping of CO₂ in dipping aquifers may allow CO₂ storage, if CO₂ is injected far enough from the outcrop of the aquifer.
DE: 1600 GLOBAL CHANGE
DE: 1847 Modeling
DE: 4455 Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, 7852)
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
SC: Hydrology [H]
MN: 2007 Fall Meeting