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This article studies the individual contribution of each term in the Navier-Stokes-Darcy (Brinkman) equation to the fluid linear momentum balance and the consequences of opting for the Darcy or Brinkman equations in 3D reactive flow simulations of a vuggy carbonate. A two-scale continuum model was used to simulate the acidification of a carbonate sample using the Darcy and Brinkman equations. Rock heterogeneity is considered in the initial porosity and permeability fields, which are calculated directly from micro-CT images. Simulations showed that the Darcy equation predicts the acid breakthrough earlier in most cases. The convective acceleration term in the Brinkman equation plays an important role in describing the fluid momentum balance at high injection velocities, and this is a clear evidence against the use of the Darcy equation to model reactive flow in such conditions.

CO2 reinjection in petroleum reservoirs brings advantages in oil production but may cause dissolution in carbonate reservoirs. Two-scale continuum models have been successfully used to simulate acidification. However, the use of realistic porosity and permeability fields in mesh simulations is still a challenge, in such a way that uniform and normal distributions have been used to generate these fields in the past. The main objective of this work was to transcript the plugs heterogeneity from the micro-CT images to simulation. The porosity field was calculated directly from micro-CT images, and two methodologies are proposed to calculate the permeability field. A reactive two-scale continuum solver was implemented in OpenFOAM and used to simulate reactive flow in two carbonate samples with different intrinsic reaction rates (calcite and dolomite). The experimental permeability evolution curves, as well as wormholes shapes and paths, are reproduced in the simulations. We observed a critical influence of specific surface area, reaction rate constant, and initial permeability field for the simulations of acidification processes.