An Investigation of Core Plug Heterogeneity Effect on Estimated Relative Permeability

Abstract A numerical study is presented to explore the impact of core plug heterogeneity on the interpretation of relative permeability (kr) curves from steady-state (SS), unsteady-state (USS), and centrifuge core-floods (CF). We consider a homogeneous core plug model and several heterogenous core plug models, where theaverage permeability of the heterogeneous models is equivalent to that of the homogeneous model. Simulation results of the heterogenous plug models are compared to equivalent homogenous models (representing the base case) to systematically evaluate the effect of core plug heterogeneity on interpreted kr curves. Any difference between the results of the heterogeneous and homogenous models should therefore be solely attributed to the heterogeneity effect. The investigation reveals that core plug heterogeneity has a significant impact on kr curves depending on how the heterogeneous portions are distributed within the rock sample. The effect may become significant in core plugs with unique characteristics such as high permeability streaks or composite nature. A composite core of varying permeability has a major effect especially on the kro curve. In core plugs with randomly distributed porosity and permeability, heterogeneity appears to have negligible impact on interpreted kr curves. The practice of selecting homogeneous plugs for special core analysis (SCAL) tests is a challenge and often becomes difficult to satisfy in core analysis studies. Instead, characterizing plug heterogeneity and including it in the interpretation of core-flood data for estimating kr curves offers an attractive and easy solution for obtaining more representative kr curves.