Pore-Network Modeling of Single-Phase Reactive Flow and Dissolution Pattern Evaluation

Mineral dissolution processes are of extreme interest for many subsurface applications such as CO₂ storage and Enhanced Oil Recovery (EOR). Modeling of the pore-scale phenomena involved in reactive flow through porous media is an important step towards understanding the changes in permeability and porosity as well different dissolution patterns observed at larger scales. The main objective of this study is to evaluate the occurrence of different dissolution patterns in a porous medium subject to various reactive flow conditions using pore network modeling (PNM). PNM is a technique that is widely used to represent natural porous media where complex pore geometries are represented using a pore-and-throat type network. The pressure field was solved by considering mass balance over each pore and assuming steady state flow of an incompressible fluid. The reactive transport problem was solved by the application of solute mass balance in each pore space: pore-bodies and throats. The geometry evolution of both pore-bodies and throats was updated based on the solute consumption by heterogeneous chemical reaction. Simulations representing a micromodel experimental porous medium showed different dissolution patterns depending on the flow conditions where the dominant transport mechanism varied from diffusive to advective. The reactivity of the solid was also modified. Dimensionless numbers were used to define each flow condition, to characterize each transport regime, and to make a phase diagram of dissolution patterns. Pore-network simulations performed in this study showed behavior that is similar to that observed by previous researchers using direct pore-scale numerical simulations. This final result highlights the applicability of the model developed in this work as a tool for the simulation of reactive transport and dissolution processes.