Pore-scale mechanics of thermal viscous fingering in miscible reactive flow displacement through porous media

Abstract This study investigates the thermal miscible displacement problem with heterogeneous reactions at the pore scale, focusing on the effects of Damköhler number ( Da ) and Lewis number ( Le ) on the dynamics of thermal viscous fingering, solid structure changes, and displacement efficiency. A critical Damköhler number ( Da ≈ 0.2) is identified, marking the transition between purely diffusion-dominated and reaction-diffusion coupled regimes. When Da < 0.2, dissolution reactions have limited impact, and final displacement efficiency ( De ) is primarily governed by Le ; increasing Le enhances thermal diffusion, smooths the temperature front, and improves De . However, when Da > 0.2, dissolution reactions significantly alter pore structures, causing a shift from multi-fingered to wormhole-type patterns as Le rises. This transition leads to an initial decline and then recovery of De within the critical Le range of approximately 2.0–4.5. Furthermore, the results reveal a notable deviation from previous REV-scale models without dissolution reactions: at Le < 2.0, reduced heat dissipation intensifies front instability and channel broadening, enhancing De , whereas at Le > 4.5, strong thermal diffusion dominates, promoting interface smoothing and improved channel connectivity to optimize De . These findings provide new insights for the design and optimization of carbon sequestration in practical applications.