Kharazmi Journal of Earth Sciences

Kharazmi Journal of Earth Sciences

Multiple Regression Analysis of the Role of Pore Throat Diameter in Determining Archie’s Parameters in Permian–Triassic Carbonate Reservoirs of the Persian Gulf

Articles in Press
Authors
Faeze Kahaneh
Vahid Tavakoli
Elham Fijani
University of Tehran
Abstract
Archie’s coefficients are among the most fundamental inputs for estimating water saturation in hydrocarbon reservoirs. However, in many reservoir evaluations, these parameters are assumed to be constant and independent of the physical characteristics of the pore network. This assumption can introduce significant uncertainty in water saturation estimation in heterogeneous carbonate reservoirs where pore and throat geometries vary considerably. In this study, the role of pore‑throat diameter in controlling variations of Archie’s coefficients in the Permian–Triassic carbonate reservoirs of the Persian Gulf is quantitatively assessed using a multiple regression approach. Core-derived porosity and permeability data, mercury injection capillary pressure (MICP) analyses, and formation resistivity factor measurements from a gas well in the western Persian Gulf were utilized. Pore‑throat diameters at various mercury saturation levels were calculated and their relationships with porosity, permeability, cementation exponent, and formation resistivity factor were evaluated. Results indicate that the pore‑throat diameter at 10 percent mercury saturation shows the strongest correlation with porosity and permeability, providing a suitable basis for rock typing. Archie’s coefficients calculated within the identified rock types demonstrate that these parameters are not constant and systematically vary with changes in pore‑network geometry. Furthermore, multiple linear regression analyses reveal that rock typing significantly improves coefficients of determination in the correlations between petrophysical and electrical properties, with the strongest improvements observed for the formation resistivity factor and cementation exponent. These findings highlight that incorporating pore‑throat diameter and rock typing offers a more robust framework for estimating Archie’s coefficients and reducing uncertainty in water saturation calculations within heterogeneous carbonate reservoirs.

Keywords
Archie’s coefficients
Pore‑throat diameter
Rock Types
Water Saturation
Carbonate reservoirs
Subjects
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Kharazmi Journal of Earth Sciences

Articles in Press, Accepted Manuscript
Available Online from 21 April 2025