HR: 0800h
AN: H11E-0339    [Abstracts]
TI: Lattice Boltzmann simulation of coupled flow and evolution of porous media at the pore scale
AU: * Kang, Q
EM: qkang@lanl.gov
AF: Hydrology, Geochemistry and Geology Group, Los Alamos National Laboratory, Los Alamos, NM 87545
AU: Zhang, D
EM: donzhang@ou.edu
AF: Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, 100 East Boyd, SEC T314, Norman, OK 73019
AU: Lichtner, P
EM: lichtner@lanl.gov
AF: Hydrology, Geochemistry and Geology Group, Los Alamos National Laboratory, Los Alamos, NM 87545
AB: Reactive flows coupled to the evolution of porous formations are a topic of great importance for a wide range of scientific problems, such as acid stimulation of petroleum reservoirs, environmental contaminant transport, mineral mining, geologic sequestration of carbon dioxide, chemical weathering, and dissolution/formation of clathrate hydrates. Because of the complexity of natural porous media and the vast span in scales needed to be addressed (the ratio between the largest and the smallest scales can be as large as 105), pore-scale simulations of the problem in a domain of macroscopic dimensions are essentially impossible even with modern supercomputers. Current modeling approaches describing reactive flows and the evolution of porous materials are based on a macro-scale continuum representation of fluid flow, transport and reaction. In these approaches, phenomenological coefficients governing macroscopic process are needed. Constitutive relations for these coefficients can be derived from the solution at the microscopic (pore) scale over a representative control volume. Thus, a detailed understanding of the phenomena at the pore scale is important for solving the problem at the macro scale of practical interest. Mineral precipitation/dissolution reactions result in physical changes of the porous medium over time with consequent changes in porosity and permeability. Clogging can result in rapid reduction in permeability without completely filling the available pore space. In this study, we present a Lattice Boltzmann model to numerically simulate coupled flow and evolution of the porous media at the pore scale and investigate changes in porosity/permeability of the medium due to mineral precipitation/dissolution. We performed a set of sensitivity tests varying the Peclet and Damkohler numbers and saturation and examined the effects of these parameters on the patterns of mineral dissolution/precipitation based on a first-order kinetic rate law or a first order heterogeneous reaction between the aqueous solution and mineral surface. Several examples are compared and contrasted ranging from reaction instability in limestone leading to the formation of wormholes, to uniform reaction over a macro scale control volume. The limitations of the applicability of the continuum formulation are discussed and constitutive relations for changes in porosity and permeability are derived.
DE: 5114 Permeability and porosity
DE: 3230 Numerical solutions
DE: 1854 Precipitation (3354)
DE: 1010 Chemical evolution
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting