Reservoir quality and expected fluids for the Ordovician Hawaz sandstone in the NC186 Concession, Murzuq Basin, Libya

The present work evaluates the Middle Ordovician Hawaz sandstone reservoir in four wells (A25-NC186, A30-NC186, H2-NC186 and H4-NC186) distributed in the NC186 Concession of Murzuq Basin, Libya. The available well log data set for each well includes: gamma ray, calliper, spontaneous potential, resistivity, density, neutron, sonic, density correction and photoelectric logs. These data have been qualitatively interpreted using Interactive Petrophysics (IP) software and quantitatively analysed by calculating different petrophysical parameters comprising; water saturation, minimum bulk volume of water, absolute permeability, critical water saturation, pressure gradient and fluid density for the promising horizons. The quantitative interpretation has revealed that three horizons (H4, H5 and H6) are suitable for further quantitative interpretation. The calculated petrophysical parameters for these horizons show that all of the studied zones represent oil reservoirs in an irreducible state (i.e. water-free oil production). This finding indicates that the remaining water is located on the pore surfaces as thin films and will not move through the production process. The results reflect excellent reservoir quality for all examined zones, including high porosity (10–26%), high permeability (42–2824 mD), low water saturation (12–43%) less than the critical water saturation (31–45%) and low BVW (0.02–0.06) less than BVW min (0.07).