The present study deals with zonation and evaluation of Ras Fanar reefs as one of the most prominent reefs in the Middle East and North Africa. The thickness of the target reservoir (Nullipore carbonate rocks) in this field ranges between 400 ft-980 ft. It consists of dolomitic limestone rich in algal fragments and unconformably overlies the Lower Eocene Thebes Formation and underlies the Middle to Upper Miocene South Gharib Formation. Wireline logs of 14 wells (KK84-1, KK84-11, KK84-12, KK84-4A, KK84-8, RF-A1, RF-A1A, RF-A2, RF-A2A, RF-A3, RF-A4, RF-B2, RF-B3 and RF-B4), capillary pressure data (Brine and Mercury Injection) and special core analyses of some cored intervals in these wells were used in this study. Furthermore, coralline algae was also incorporated together with other logging data and used for Nullipore reservoir zonation. It is found that Nullipore reservoir consists of 3 electro-lithofacies (zones I, II and III) each of which exhibits its own petrophysical characters. Zone (II) is considered the most important and mostly characterized by high well connected pore-space system and high hydrocarbon saturation as compared with the other zones.
Hydrocarbons potentialities (pore space distribution, fluid saturation and pay cutoffs) of the Nullipore reservoir rocks are evaluated and the different deduced parameters are represented in a number of vertical analogs, lateral distribution maps and pay cutoff plots. Based on petrophysical analyses, it is found that Nullipore reservoir rocks consist of two lobes (A and B) extending in a northwest-southeast direction. Inside these lobes, the hydrocarbon saturation increases gradually towards the center. However, the (B) lobe was found to be of better reservoir quality than the (A) lobe. Porosity and water saturation values of 14 % and 64 %, respectively, are used as the net pay cutoffs in Nullipore reservoir rocks.