Field-scale hydrodynamics and optimization of CO₂ storage in saline aquifers using a hybrid Darcy scale flow–RSM approach

Geological CO₂ storage in saline aquifers is a promising strategy for mitigating climate impacts from industrial emissions, yet its effectiveness depends on understanding how operational and reservoir parameters jointly influence plume dynamics and storage efficiency. This study introduces a high-fidelity DSF–RSM framework that couples Darcy-scale flow simulations with response surface methodology to evaluate the roles of injection flow rate (10–90 kg/s), injection duration (20–60 years), and initial brine saturation (0.1–0.5) in controlling CO₂ migration and volumetric sweep efficiency. The results identify three flow regimes governed by the balance of viscous, capillary, and buoyancy forces: a capillary-dominated regime at low injection rates (<30 kg/s), a viscous-dominated regime at high rates (>65 kg/s), and an optimal intermediate regime (50–60 kg/s, brine saturation 0.25–0.30) in which 60–70 % of the reservoir is efficiently swept with minimal fingering and reduced energy input within the modeled domain. Energy dissipation increases sharply with brine saturation—from 2.32 × 10⁻³ W/m³ at S = 0.1 to 12 × 10⁻³ W/m³ at S = 0.5—reflecting transitions in the dominant flow mechanisms. Statistical validation confirms strong predictive performance of the DSF-RSM surrogate model (R² = 0.9872, SD = 1.51, RMSE = 0.004), and sensitivity analysis identifies injection flow rate as the most influential parameter. Overall, this work provides new insights into the hydrodynamic controls on CO₂ plume migration and offers a rigorous framework for designing efficient, field-scale storage strategies.