CO2-brine displacement in heterogeneous carbonates

The displacement of brine by CO2 is an important process controlling plume migration and initial pore-space utilization in geological CO2 storage. We present CO2-brine unsteady-state core flood experiments to characterize CO2-brine primary displacement in Estaillades limestone, a model system for dual-porosity carbonates. We analyze the experiments by means of numerical simulations assuming 2-D homogeneous rock and parameterized kr(SW) relationships. Assisted history matching methodologies were used to find the kr(SW) parameters which minimize a mismatch function, giving the best match to the experimental data. We refer the results to the microscopic rock structure and we discuss the limits of applicability. Larger-scale heterogeneity was considered as intrinsic to arrive at a practical and upscaled description of the displacement process. Heterogeneity is discussed by comparing the results to classical relative permeability measurements on samples with a 24× smaller volume, which are less affected by heterogeneity. We found that larger-scale heterogeneity results in lower fluid-phase mobilities.