Relative permeability prediction considering complex pore geometry and wetting characteristics in carbonate reservoirs

The measurement of relative permeability in carbonate rocks is very uncertain because of the complex pore system. Several equations for the relative permeability have been previously developed. However, most equations assume a single pore system that cannot be applied accurately. This study presents a relative permeability estimation method that considers capillary pressure, contact angle, pore size distribution, and residual oil saturation with respect to the heterogeneous pore network. As results, the capillary pressure was observed to have different tendencies for macropore and micropore. Also, the pore size distribution index of the macropore system was greater than the micropore system. For the macropore, water has a higher relative permeability than oil; a small reduction in oil saturation can easily flow water. In contrast, the micropore tends to follow the conventional relative permeability curve. Therefore, stable water displacement was not assured, leading to an early breakthrough for the heterogeneous carbonate rocks.