Development of scaling parameters to describe CO2–rock interactions within Weyburn-Midale carbonate flow units

The purpose of this research was to calibrate relationships between porosity, permeability, and carbonate rate laws for two distinct carbonate rock types from the Weyburn-Midale field against experimental and characterization measurements. Subcores from the Midale Marly dolostone and Vuggy limestone reservoir flow units were reacted with brines equilibrated with pCO2 = 3 MPa at 60 °C and simulated from the micron to centimeter scale using 3D reactive transport models. Our results indicate that laboratory-derived dissolution rate equations, rate constants, activation energies, and thermodynamic solubility constants can be used to describe the observed calcite and dolomite dissolution, but rate constants may need to be adjusted to account for order of magnitude uncertainties in the initial effective surface area measurements. Successful modeling required empirically estimating the effective grid permeability for heterogeneous samples in which much of the porosity is below the resolution of the 3D imaging of the cores. Porosity and permeability relationships were also dependent on sample pore structure and its heterogeneity. These correlations were fitted by a power law with exponent n equal to 3 and 8 for the more homogeneous Marly dolostone and the highly heterogeneous Vuggy limestone, respectively.

► We modeled changes in porosity and permeability for two distinct carbonate rocks reacted with CO2-rich brines.
► Use of laboratory-derived rate and solubility parameters are valid given initial surface area.
► Successful modeling required empirically estimating the effective grid permeability for heterogeneous samples.
► Porosity and permeability relationships were also dependent on sample pore structure.