Retraction of dissolution front in natural porous media

Abstract

The dissolution of porous materials in a flow field shapes the morphologies of many geologic landscapes. Identifying the dissolution front, the interface between the reactive and the unreactive regions in a dissolving medium, is a prerequisite for studying dissolution kinetics. Despite its fundamental importance, the dynamics of a dissolution front in an evolving natural microstructure has never been reported. Here we show an unexpected spontaneous migration of the dissolution front against the pressure gradient of a flow field. This retraction stems from the infiltration instability induced surface generation, which can lead to a reactive surface dramatically greater than the ex situ geometric surface. The results are supported by a very good agreement between observations made with real time X-ray imaging and simulations based on static images of a rock determined by nanoCT. They both show that the in situ specific surface area of natural porous media is dependent on the flow field and reflects a balancing between surface generation and destruction. The reported dynamics challenge many long-held understanding of water-rock interactions and shed light on reconciling the discrepancies between field and laboratory measurements of reaction kinetics.

arXiv comment20 pages, 3 figures

References in corpus (7)

• Wormhole formation in dissolving fractures
• Reactive-infiltration instabilities in rocks. Fracture dissolution
• Network models of dissolution of porous media
• Instabilities in the dissolution of a porous matrix
• Direct observation of coupled geochemical and geomechanical impacts on chalk microstructural evolution under elevated CO2 pressure. Part I
• Dissolved CO2 stabilizes dissolution front and increases breakthrough porosity of natural porous materials
• Reactive infiltration instability amplifies the difference between geometric and reactive surface areas in natural porous materials

Cited by in corpus (4)

• Direct observation of coupled geochemical and geomechanical impacts on chalk microstructural evolution under elevated CO2 pressure. Part I
• Temporal pattern of entropy production induced by reactive infiltration instability in natural porous media
• Momentary increase in reactive surface area in dissolving carbonate
• Path selection during wormhole growth