Role of Pore and Pore‐Throat Distributions in Controlling Permeability in Heterogeneous Mineral Dissolution and Precipitation Scenarios

• Published in: Water resources research Vol. 55; no. 7; pp. 5502 - 5517
• Main Authors: Steinwinder, Jeffrey, Beckingham, Lauren E.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01-07-2019
• Subjects: Chemical precipitation; Computer simulation; Dissolution; Dissolving; Evolution; Grain size distribution; Membrane permeability; mineral dissolution; mineral precipitation; Network topologies; Permeability; pore network modeling; pore size distributions; pore‐throat distributions; Porosity; Porous media; Precipitation; Spatial distribution; Throats; Topology
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2019WR024793

Mineral dissolution and precipitation reactions can significantly alter the porosity and permeability of porous media. While porosity generally increases with dissolution and decreases with precipitation, permeability is controlled by the spatial locations of reactions in discrete pores and pore throats and in the greater pore network. Geochemical reactions have been observed to occur both uniformly and nonuniformly in porous media, driven by parameters such as mineral distribution, grain size, and Peclet and Damkohler numbers. Pore network modeling can be used to simulate the impact of pore‐scale alterations on permeability, requiring only pore and pore‐throat size distributions and pore connectivity. Here, the impact of variations in pore and pore‐throat size distributions on reactive permeability for uniform and nonuniform spatial distributions of reactions is evaluated. A series of pore network models are created and populated with pore and pore‐throat size distributions of varying types (skewed, normal, and uniform) to represent differences in network topology and characterization methods. The impacts of these distributions on reactive permeability are then simulated for uniform and nonuniform reaction conditions by increasing or decreasing pore and pore‐throat sizes in a prescribed manner to reflect dissolution and precipitation, respectively. Overall, simulations reveal that porosity‐permeability evolution varies with reaction scenario and is qualitatively consistent for the different pore and pore‐throat size distributions. Common macroscopic porosity‐permeability relationships work well for some reaction scenarios but are unable to reflect size‐dependent reactions. A new modified version of the Verma‐Pruess relationship is created and able to successfully reflect the porosity‐permeability evolution for size‐dependent reactions.
Key Points
Porosity‐permeability evolution depends on the spatial location of mineral dissolution and precipitation reactions
Similar porosity‐permeability evolutions observed for most reaction scenarios regardless of pore and pore‐throat size distributions
A new modified Verma‐Pruess equation reflects simulated porosity‐permeability in size‐dependent scenarios, not fit by common relationships