This study was carried out to investigate the general geological setting, structure setup and petrophysical characteristics (Ф, Rw ,Rt , Sw , Sh , Shr , Shm) for Saar-Naifa reservoir rocks using conventional and advanced logging tools. Several steps were done such as developing lithology saturation and lithologic identification cross plots, introducing the lateral variation of the lithology and the different saturation distribution in the Saar-Naifa reservoir. The porosity analysis of the investigated area indicated that the average effective porosity of the Saar-Naifa reservoir varied from 11 to 15% and the water saturation of the Saar-Naifa reservoir ranged between 12 and 38%. On the other hand, hydrocarbon saturation matches well with water saturation in a reverse relationship. From these results, it could be concluded that the Saar-Naifa reservoir represents the main producing zone in the studied area.
The gamma ray spectrometry is used to determine the stability of radioactive elements, shale volume and clay type. Three spectrometric variables eU, eTh and K% are recorded in nine wells of Saar-Naifa reservoir in Hiswah oil field. Statistical analysis of the radioactive elements (uranium and thorium) reflects their concentrations in Saar-Naifa reservoir. Spectral gamma ray log analysis results indicate that the clay minerals of Saar-Naifa reservoir are chlorite, montmorillonite, kaolinite and mixed layered clay. Well log analysis reflects that the Saar-Naifa. reservoir is composed mainly of limestone and minor shale and acts as a good reservoir for hydrocarbon accumulation.