Appropriate relative permeability curves for two-phase flows through heterogeneous vuggy carbonates remain unclear. We have therefore conducted numerical oil-water two-phase flow simulations using X-ray CT data, to obtain relative permeability curves for different types of vuggy carbonate samples. 3D distributions of CT number of the samples, which consist of 400-μm cubic voxels, are converted into 3D porosity distributions, and corresponding 3D distributions of absolute permeability are obtained by assuming porosity-permeability relations of non-vuggy carbonates at the voxel scale. 3D distributions of water saturation at different global water saturation levels for different capillary pressure conditions are obtained for the porosity distributions, by assuming porosity-dependent capillary pressure curves of non-vuggy carbonates at the voxel scale, providing corresponding 3D distributions of oil and water relative permeabilities with an assumption of Corey-type relative permeability curves at the voxel scale. Darcy flow simulations for resultant distributions of oil and water effective permeabilities provide global oil and water relative permeabilities at various global water saturation levels (i.e., relative permeability curves), which are validated by two-phase flow experiments. As a result, relative permeability curves of the samples containing vug pores distributed over the entire body exhibit Corey-type behaviors. On the other hand, relative permeability curves of the samples containing vug pores having fracture-like 2D distributions exhibit ν-type behaviors, which has been observed for two-phase flows through rock fractures. In case of vuggy carbonates, there is a possibility to have the non-Corey-type relative permeability curves, which are characterized by quite different behaviors of non-wetting phase from those of Corey type, depending on the distribution of vug pores because vug pores of weaker capillarity strongly affect behaviors of non-wetting phase.
Relative Permeability Curves for Two-Phase Flows Through Heterogeneous Vuggy Carbonates
Kusanagi, Hikaru, Watanabe, Noriaki, Shimazu, Takashi, and Masahiko Yagi. "Relative Permeability Curves for Two-Phase Flows Through Heterogeneous Vuggy Carbonates." Paper presented at the SPWLA 22nd Formation Evaluation Symposium of Japan, Chiba, Japan, September 2016.
Download citation file: