Evaluation of Macroscopic Porosity‐Permeability Relationships in Heterogeneous Mineral Dissolution and Precipitation Scenarios

Abstract

AbstractMineral dissolution and precipitation reactions may alter porosity and permeability in porous media. While porosity generally increases with mineral dissolution and decreases with precipitation, corresponding permeability alterations are complex and predictive capabilities remain limited. The evolution of permeability depends on the spatial locations of geochemical reactions, both in individual pores and in the greater pore network and a range of reaction patterns have been observed in prior experimental investigations. Macroscopic relationships are needed in core‐to‐field scale reactive transport simulations that can accurately simulate permeability evolutions resulting from pore‐scale reactions. Currently, empirical porosity‐permeability relationships, such as the Kozeny‐Carman equation, are widely used to predict permeability evolution. However, these relationships only allow for a single permeability value for each porosity value and the validity of these relationships for the various spatial distributions of pore‐scale alterations is unknown. Using pore network model simulations, changes in permeability resulting from a range of dissolution and precipitation patterns (uniform, random, channelized, and size‐dependent) in a sandstone sample are investigated. The validity of macroscopic porosity‐permeability relationships for these reaction scenarios is evaluated by comparing computed permeability values with pore model simulations. Simulation results exhibit a large variation in porosity‐permeability relationships among reaction scenarios. Macroscopic porosity‐permeability relationships work well for uniform reaction scenarios where the extent of reaction is related to the pore size. The porosity and permeability relationships that result from more complex pore‐scale alterations, including pore size‐dependent reactions however, cannot be captured using these empirical relationships.