Quantifying Dissolution Dynamics in Porous Media Using a Spatial Flow Focusing Profile

• Published in: Geophysical research letters 2024-10, Vol.51 (20), p.n/a
• Main Authors: Szawełło, Tomasz, Hyman, Jeffrey D., Kang, Peter K., Szymczak, Piotr
• Format: Article
• Language: English
• Subjects: Carbon sequestration; Channels; Chemical kinetics; Chemical reactions; Dissolution; Dissolving; Earth Sciences; flow focusing; Flow rates; Heterogeneity; Kinetics; Numerical simulations; Phase diagrams; Porous media; porous media flow; Qualitative analysis; Radioactive wastes; Reaction kinetics; reactive transport; Temporal variations; Waste storage
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL109940

The diverse range of patterns in porous media formed by dissolution processes depends on the relative magnitude of flow, transport, and chemical reactions at pore surfaces. However, distinguishing between regimes often relies solely on qualitative, visual comparisons of emergent structures. Here, we propose a quantitative measure capable of identifying different regimes using the concept of the spatial flow focusing profile, which segments the medium into cross sections along the flow direction to calculate the flow focusing index for each section. We employ this measure in numerical simulations of a dissolving porous medium using a pore network model. We obtain a morphological phase diagram of dissolution patterns, which we characterize using the flow focusing profile. In particular, we demonstrate that analyzing the temporal changes in the profile allows one to quantitatively distinguish between wormholing and channeling. The transition between them is shown to be affected by the heterogeneity of the system. Plain Language Summary When rock dissolves, it creates different patterns depending on the interplay of flow, reactant transport, and chemical kinetics. These patterns are classified into various types, known as dissolution regimes. However, this classification is often based solely on visual examination of the final structures and lacks quantitative criteria. In this study, we propose a tool that considers cross sections of the material and measures the focusing of flow in each slice. For example, flow can be uniform across most of the cross section or focused in a small number of channels. Based on how this flow focusing changes in space and time, we assign the patterns to dissolution regimes. Using this tool, we demonstrate that accurately describing the patterns resulting from dissolution requires knowledge of their evolution history. Predicting dissolution regimes for a given flow rate, reaction rate, and pore geometry is essential in practical applications, such as geological carbon sequestration or nuclear waste storage, where the emergence of highly conductive dissolution channels must be prevented at all costs. Key Points Dissolution regimes can be quantitatively distinguished using the concept of the flow focusing profile Temporal changes of the flow focusing profile differentiate the wormholing and channeling regimes Pore structure heterogeneity shifts the transition between dissolution regimes