PETROPHYSICAL EVALUATION FOR THE RESERVOIR UNITS OF NAHR-UMR FORMATION IN THE LUHAIS OIL FIELD SOUTH OF IRAQ
Nahr-Umr Formation is considered as one of the most important formations deposited during the Cretaceous period and it is one of the main producing reservoirs in southern Iraq and neighboring regions, so it was selected to study and evaluate its petrophysical properties (primary, secondary and effective porosity, permeability, water saturation and movable and residual oil saturation) by employing well logs data interpretation )GR, RHOB, NPHI, Dt, Rt, Rxo(. The study included results of well logs analysis of three wells from Luhais oil field (Lu-5, Lu-18, and L-36). Depending on the calculated petrophysical properties; the formation was divided into three main reservoir units, the first one is the upper Nahr-Umr reservoir unit (NRA) which was subdivided into four reservoir subunits (S11, S12, S13, S14), the second one is the middle Nahr-Umr reservoir unit (NRB) which was subdivided into three reservoir subunits (S21, S22, S23), and the third one is the lower Nahr-Umr reservoir unit (NRC), that was subdivided into three subunits (S31, S32, S33, S34, S35). The performance of the reservoir subunits in terms of their economic productivity was determined. The best of these reservoir subunits in most of the study wells were (S11, S14, S23, S31, and S32).