Optimizing injection parameters in mineral replacement systems

Mineral replacement processes often involve coupled dissolution-precipitation reactions, where a primary mineral is replaced by a secondary one. These transformations are governed by strong, nonlinear interactions among chemical reactions at rock surfaces, evolving pore geometries, and the development or closure of flow pathways. Maintaining a steady influx of reactants and efficient removal of products is crucial for sustaining reaction progression, but issues such as passivation layer formation or flow channel blockage by precipitates frequently disrupt this balance. This problem is particularly relevant in the context of mineral trapping of CO₂, where chemical reactions lead to an increase in solid volume. Consequently, determining optimal injection rates becomes crucial for enhancing the efficiency of the process. To address these challenges, we propose a numerical framework designed to simulate hydrochemical transformations within porous media.

In our simulations, we examine a medium infiltrated by a reactive fluid that triggers coupled dissolution-precipitation reactions at pore surfaces. We model the porous medium as a system of interconnected pipes [1], with the diameter of each segment changing depending on the local consumption of reactants. We incorporate nonlinear kinetics of chemical reactions into the model and assess the impact of inlet reactant concentrations on the behavior of the system. During evolution, we also modify the network topology by merging connections when pore distances are comparable to pore sizes and by cutting connections when pores become clogged.

We explore possible dissolution-precipitation regimes in search of parameters optimal for mineral replacement. By varying the flow rate and the concentrations of injected species, we analyze the emergent patterns to construct a morphological diagram. We benchmark the results against experimental data on calcium carbonate dissolution and gypsum precipitation [2]. We are particularly interested in regimes with oscillating permeability, where the reaction is self-limiting—precipitates clog the pores, but the system continually creates new flow pathways, maintaining reaction progress. We quantitatively characterize various evolution regimes, measuring the volume of replaced mineral and assessing the development of flow pathways [3]. Through this analysis, we identify a region in the space of injection parameters that maximizes mineral replacement.

 

[1] A. Budek and P. Szymczak, Physical Review E, 86, 056318, 2012.
[2] O. Singurindy and B. Berkowitz, Water Resources Research, 39, 1016, 2003.
[3] T. Szawełło, J. D. Hyman, P. K. Kang, and P. Szymczak, Geophysical Research Letters, 51, e2024GL109940, 2024.