Smoothed particle hydrodynamics model for pore-scale flow, reactive transport and mineral precipitation.

Abstract

We have developed a pore-scale numerical reactive transport model, based on smoothed particle hydrodynamics (SPH), that incorporates heterogeneous precipitation/dissolution reactions. Lagrangian particle methods such as SPH have several advantages for modeling pore-scale flow and transport: i) in a Lagrangian framework there is no non-linear term in the momentum conservation equation, so that SPH allows accurate solution of momentum dominated flows; ii) complicated physical and chemical processes associated with realistic equations of state, changes in solid boundaries due to dissolution or precipitation and chemical reactions are easy to simulate. The SPH model was used to study the general effects of porosity, pore scale heterogeneity, Damkohler numbers and Peclet numbers on reactive transport and to estimate effective reaction coefficients and mass transfer coefficients. The changes in porosity, conductivity and transport parameters resulting from mineral precipitation were also investigated. Hysteresis in the reaction rate coefficient and mass transport coefficient resulting from changing porosities, mass fluxes and reactive surface areas was observed. Flow and transport with low Damkohler numbers and high Peclet numbers was found to result in uniform precipitation. When the Damkohler number was high and the Peclet number was low, precipitation occurred mainly around the supersaturated solution injection areas. The pore-scale model was coupled with a continuum-scale reactive transport model and tested using data from a mesoscale experimental investigation of calcite precipitation in a porous medium. The results of the coupled pore-continuum modeling approach are compared to simulation results from continuum-scale modeling alone with existing formation damage models drawn from the literature, and to the experimental observations.