Speaker
Description
Mineral precipitation triggered by mixing of chemically incompatible fluids produces low-permeability barriers that progressively alter subsequent transport and reaction. While the macroscopic hydraulic consequences have been documented experimentally, the pore-scale mechanisms by which an established boundary regulates the mixing efficiency of the reactive fluids remain poorly characterized.
This study uses pore network modeling to investigate how a precipitation boundary affects reactive mixing between two parallel reactant streams across diffusive-advective regimes. The network was extracted from a high-resolution XRCT image of Berea sandstone in which mineral precipitation had been induced experimentally. Two configurations were compared — a pristine network with digitally restored pore space and an obstructed network retaining the precipitate as a microporous phase — at three Péclet numbers (Pe = 0.1, 1, and 10).
Simulation results show suppressed mixing across the precipitation boundary at all Pe, but the level of suppression is strongly regime-dependent with respect to the injected pore volume. It is maximal at intermediate Pe, where the boundary confines subsequent reaction to a narrow band; modest at low Pe, where diffusive fluxes are similar across the two network configurations; and marginal at high Pe, where advective segregation already limits mixing. At matched pore volumes, the diffusion-dominated regime produces the most cumulative precipitation, reflecting longer residence times and stronger transverse diffusive exchange. The precipitation boundary acts not as a simple mixing suppressor but as a temporal regulator, preserving steeper concentration gradients and sustaining higher late-stage precipitation rates than the pristine network.
These findings link pore-scale mixing dynamics to macroscopic formation damage and indicate that significant precipitate accumulation can develop in far-field zones where diffusion-dominated mixing prevails.
| Country | Switzerland |
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