Random-walk modeling of reactive transport in porous media with a reduced-order chemical basis of conservative components

In this work we employ a reduced-order basis of conservative chemical components to model reactive transport using a Lagrangian (particle tracking) method. While this practice is well-understood in the Eulerian (grid-based) context, its adaptation to a Lagrangian context requires a novel reformulation of particle transport properties. Because the number of conservative-species particles need not change during simulation, spatial resolution stays constant in time, and there is no increase in computational expense due to increasing numbers of product particles. Additionally, this treatment simplifies the interaction between equilibrium and kinetic reactions and allows the use of species-dependent transport operators at the same time. We apply this method to model a suite of simple test problems that include equilibrium and kinetic reactions, and results exhibit excellent match with base-case Eulerian results. Finally, we apply the new method to model a 2D problem concerning the mobilization of cadmium by a CO2 leak, showing the potential applicability of the proposed methodology.The authors thank Nicolae Suciu and two anonymous reviewers for their very useful comments and suggestions. This work was supported by the US Army Research Office under Contract/Grant W911NF-18-1-0338, as well as by the Spanish Ministry of Economy and Competitiveness through projects WE-NEED (PCIN-2015-248) and INDEMNE (CGL2015-69768-R). Sandia National Laboratories is a multi-mission laboratory managed and operated by the National Technology and Engineering Solutions of Sandia, L.L.C., a wholly owned subsidiary of Honeywell International, Inc., for the DOE's National Nuclear Security Administration under contract DE-NA0003525.Peer ReviewedPostprint (published version