Permeability Estimation and Reservoir Characterization Using the Hydraulic Flow Unit (HFU) Approach: A Case Study of the Paleocene Beda C Carbonate Reservoir, Sabah Oil Field, Sirte Basin

Abstract

Permeability determination in carbonate reservoirs represents a major challenge in petroleum engineering due to severe rock heterogeneity resulting from complex depositional histories and diagenetic modifications. Core samples are typically available for only a limited number of wells due to high acquisition costs. Consequently, developing low-cost, accurate, and reliable predictive models for permeability is paramount for efficient reservoir management and development strategies. This paper presents a comprehensive study to establish an optimal permeability predictive model for the Paleocene Beda C formation within the Sabah Oil Field, located in the Sirte Basin, Libya. Data collected from eight cored wells were analyzed using the Hydraulic Flow Unit (HFU) methodology, which is based on the modified Kozeny-Carman equation and the Flow Zone Indicator (FZI) concept. Traditional empirical formulations (Timur, Wyllie-Rose, and Morris-Biggs) as well as classical regression models (linear, power, and exponential) were applied and statistically compared against the HFU method. The results demonstrate that traditional porosity-permeability correlations exhibit low predictive capability due to the highly scattered nature of carbonate petrophysical trends. In contrast, the HFU method effectively classified the heterogeneous reservoir into four distinct flow units, each characterized by unique pore-throat geometrical attributes. The HFU-derived models achieved high accuracy with coefficients of determination (R2 ≥ 0.70). The developed framework was successfully validated through application to well logging data from the un-cored well G-18, offering a robust tool for fields-wide permeability prediction. Keywords: Carbonate Reservoir, Permeability Estimation, Hydraulic Flow Unit (HFU), Flow Zone Indicator (FZI), Sirte Basin, Reservoir Heterogeneity.