Modified Kozeny–Carmen correlation for enhanced hydraulic flow unit characterization

Although several techniques have been proposed to predict permeability using porosity–permeability relationships, the Kozeny–Carmen (K–C) correlation is the most widely acceptable methodology in the oil industry. Amaefule et al. (1993) modified that correlation introducing the concept of Reservoir Quality Index (RQI) and Flow Zone Indicator (FZI) to enhance its capability to capture the various reservoir flow behavior based on its respective characters. Yet, there are challenges in using the original correlation due to its inherent limitations and over simplified assumptions that prevent accurate Hydraulic Flow Unit (HFU) definitions. This research addresses some of those shortcomings and proposes a modified K–C correlation by handling the tortuosity term in a more robust manner. Core data from major carbonate reservoirs in Saudi Arabia is used to test the model. Additional data sets obtained from literature on sandstone reservoirs are used as well to demonstrate the global applicability of the proposed model. Results show that more permeability variations are to be expected within a given HFU. Moreover, the conventional model underestimates permeability values within a specific HFU significantly in comparison with the new model.

► Kozeny–Carmen equation ignores the inherent nonlinearity of tortuosity and porosity.
► Tortuosity is approximated from the formation resistivity and porosity.
► A novel permeability–porosity model is proposed.
► The proposed model captures the nonlinearity of tortuosity more efficiently.
► The conventional model underestimates permeability within a HFU.