HR: 11:20h
AN: H12A-05    [Abstracts]
TI: Numerical Upscaling of Relative Permeability in Fractured Porous Media
AU: * Matthai, S K
EM: s.matthai@imperial.ac.uk
AF: Imperial College London, Dept. Earth Science & Engineering South Kensington Campus Exhibition Road, London, SW7 2AZ, United Kingdom
AB: Fractured reservoir relative permeability, water-breakthrough and recovery cannot be extrapolated from core samples, but computer simulations allow their quantification using discrete fracture models at an intermediate scale. For this purpose, we represent intersecting natural and stochastically generated fractures in massive or layered porous rock with an unstructured hybrid finite element grid. We compute two-phase flow with an implicit finite element - finite volume method (FEFVM) to identify the emergent properties of this system. The results offer many important insights: Total mobility is low over a wide saturation range and very sensitive to small saturation changes. When fractures dominate the flow, but fracture porosity is low (10^-4-1\(% \)), grid- block average relative permeabilities, krawg, cross-over during saturation changes of less than one percent. Such upscaled krawg yield a convex, highly dispersive fractional flow function without a shock. Its shape can not be matched with any conventional model and a new formalism based on the fracture-matrix flux ratio will be presented. Counter-current imbibition (CCI) during water flooding occurs only over a small fraction of the total fracture-matrix interface area because water imbibes only a limited number of fractures. Only in some fractures, flow will be sufficiently fast for CCI to significantly enhance recovery. CCI leads to a rate dependence of recovery and water breakthrough which occurs earlier in transient- than in steady state flow. We show how such effects can be included into a new relative permeability model for fractured porous media.
UR: http://csmp.ese.imperial.ac.uk/wiki
DE: 1899 General or miscellaneous
DE: 3225 Numerical approximations and analysis (4260)
DE: 3238 Prediction (3245, 4263)
DE: 3653 Fluid flow
DE: 4430 Complex systems
SC: Hydrology [H]
MN: 2007 Fall Meeting