Petrophysical Evaluation of Potential Reservoirs Through Petrography and Digital Image Analysis: Case of Miocene Deposits From the Cap Bon, Northeastern Tunisia

Abstract

ABSTRACT Miocene siliciclastic reservoirs of northeastern Tunisia provide key analogues for Mediterranean hydrocarbon systems, yet pore architecture and flow behaviour remain insufficiently constrained. In the Eljabouza area (Cap Bon), the Fortuna (Chattian‐Aquitanian) and upper Beglia (Serravallian) formations were evaluated by coupling rock fabric with directional petrophysical measurements on 132 oriented cubes from 18 outcrop samples. Facies and rock‐fabric analysis enable the identification of nine facies and six rock types in the Fortuna and eight facies and three rock types in the Beglia deposits. Quartz dominates with accessory feldspar, iron(hydr)oxides and clays. Localised feldspar dissolution generates secondary porosity. Petrophysical properties range from tight sands ( Φ < 2%, K < 15 mD) to highly permeable units ( Φ > 20%, K > 1 D) in the Fortuna deposits, while the Beglia Formation shows more uniform and generally favourable quality ( Φ up to ~26%, K to ~3 D). Permeability is strongly anisotropic with consistently higher values along the X and Z axis reflecting directional grain scale fabric characterised by aligned grain contacts and preferentially oriented intergranular pore throats parallel to bedding and cross‐ lamination at plug scale. Pore type control is decisive as primary intergranular pores provide storage and effective flow paths, whereas dissolution‐related secondary porosity markedly enhances connectivity and offsets low to medium porosity, quantified through Digital Image Analysis (DIA). Pore geometry (shape factor γ ≈ 1.1–2.4) displays weak correlation with K and sub‐resolution microporosity contributes appreciably to flow capacity. Overall, reservoir performance across the Fortuna‐Beglia system is governed by the interplay of rock fabric, directional permeability and pore type partitioning. The Beglia Formation generally outperforms the Fortuna Formation, whose heterogeneity implies potential compartmentalization. These results underscore the importance of accounting for measurement orientation and pore type distinctions across different resolutions when upscaling to predict flow in similar siliciclastic reservoirs.