Assessing the unconventional reservoirs of the Nukhul formation in the Rudeis-Sidri Field, Gulf of Suez: petrophysical characterization and flow unit discrimination

Abstract This study employed an integrated petrophysical workflow that combines conventional well-log interpretation with routine core analysis to evaluate the Nukhul Formation in the Rudeis–Sidri Field and to assess its hydrocarbon potential quantitatively. The Sidri-14 well, Gulf of Suez, penetrates the Lower Miocene Nukhul Formation, a sequence of sandstone, shale, and limestone. Petrophysical evaluation, supported by core (215 samples) and well log analysis, subdivided the formation into four reservoir units (A–D). Units A, B, and C exhibit low porosity (4.3–13.6%), and low permeability (0.03–13.099 mD), with a heterogeneity coefficient (V) of 0.92, classifying the formation as highly heterogeneous with variable but moderate hydrocarbon saturation, while water saturation (Sw) frequently exceeds 50%, limiting net pay, whereas Unit D, being carbonate-dominated, shows no reservoir potential. The porosity–permeability relationship (R 2 = 0.93–0.98) confirms that permeability is strongly controlled by pore-throat size. By employing hydraulic flow unit (HFU) classification (via RQI, NPI, FZI, and stratigraphic Lorenz techniques), most samples fall within tight/poor quality domains (RQI < 0.25 μm, R 35 < 1 μm), requiring stimulation for economic recovery. Hydraulic Flow Unit (HFU) classification subdivides the reservoir into 8 HFUs, where HFU-1 and HFU-2 contribute the largest portion of flow (14.11% and 16.52% of total flow capacity) and equivalent to PSRT1 and PSRT2 , which are characterized by the highest RQI and FZI values, wide pore-throat sizes, high permeability, and excellent flow capacity, while HFU-8 contributes 0%, highlighting uneven productivity distribution. This integration reveals that the Nukhul Formation is classified as an unconventional, tight reservoir with limited but heterogeneous hydrocarbon potential. Productive intervals exist but are restricted to specific HFUs, meaning advanced recovery techniques (hydraulic fracturing, horizontal drilling) are essential for efficient hydrocarbon exploitation.