Rock-fluid dynamics under impurity-bearing CO₂ injection: conservative shock-capturing simulations of reactive fronts

We present a thermodynamically admissible modelling and simulation framework for hydro-mechanical-chemical (HMC) processes in deformable porous rocks undergoing mineral reactions. The approach targets regimes with extreme localization in time and space, where sharp reaction fronts (shocks) propagate and where reaction-induced property contrasts (e.g., density, porosity, permeability) strongly impact flow.

The model couples multicomponent reactive transport to local equilibrium thermodynamics and is designed to remain robust under large reaction-driven density changes typical of (de)hydration/(de)carbonation, and impurity-driven acidification during CO₂ storage. The numerical algorithm is conservative, ensuring stable solutions in the presence of discontinuities and steep gradients, and is implemented using accelerated solvers with GPU-optimized kernels for high throughput in memory-bound reactive transport problems.

We provide a suite of verification benchmarks for the numerical scheme, including comparisons against analytical solutions for chemically driven metamorphic fronts, as well as compaction-driven infiltration scenarios. Demonstration cases cover: (i) compaction-driven fluid focusing, (ii) (de)carbonation waves, and (iii) multicomponent aqueous systems relevant to CCS, including more than 50 charged species. For CO₂ storage applications, we explicitly evaluate impurity-bearing injection streams and show how buffering by mineral assemblages controls pH and limits unrealistic acidification predicted by reduced-chemistry models.

Overall, the framework enables high-resolution, physically consistent HMC simulations that resolve steep fronts without numerical errors and provide a basis for predictive assessment of injectivity evolution, reaction localization, and trapping efficiency for impurity-tolerant CO₂ injection strategies.