Numerical studies and analysis on reactive flow in carbonate matrix acidizing

Matrix acidizing is a stimulation technique to improve oil recovery in carbonate reservoirs. In this work, a new two-scale continuum model is used to study acidizing process in radial flow. Naiver-Stokes_Darcy equation is adapted to quantity fluid velocity instead of Darcy's law. Furthermore, the continuity equation of fluid phase is redeveloped to consider mass exchange between fluid and solid phases. Based on this model, several numerical case studies are conducted to ascertain effect of acid and rock physical parameters. Results show that acidizing process is obviously affected by acid injection velocity and acid surface reaction rate. Ignoring the mass exchange term between fluid and solid phases results in an overestimation of pore volume to breakthrough. Darcy's law is not applicable when acid is injected into core sample at low velocity. Pore volume to breakthrough calculated by original two-scale continuum model based on the Darcy equation is much lower than that calculated by updated two-scale continuum model based on Naiver-Stokes_Darcy equation with low acid injection velocity. The simulation results are compared with available experimental data and are found to keep a consistent pattern.