This study aims to integrate sedimentological, log and core analyses data of the Middle Miocene Nullipore
Formation at the Ras Fanar Field (west central Gulf of Suez, Egypt) to evaluate and reconstruct a
robust petrophysical model for this reservoir. The Nullipore Formation attains a thickness ranging from
400 to 980 ft and represents a syn-rift succession of the Middle Miocene marine facies. It consists of
coralline-algal-reefal limestone, dolomitic limestone and dolostone facies, with few clay and anhydrite
intercalations. Petrographically, seven microfacies types (MF1 to MF7) have been recognized and
assembled genetically into three related facies associations (FA1 to FA3). These associations accumulated
in three depositional environments: 1) peritidal flat, 2) restricted lagoon, and 3) back-shoal environments
situated on a shallow inner ramp (homoclinal) setting. The studied rocks have been influenced by
different diagenetic processes (dolomitization, cementation, compaction, authigenesis and dissolution),
which led to diminishing and/or enhancing the reservoir quality. Three superimposed 3rd-order depositional
sequences are included in the Nullipore succession displaying both retrogradational and aggradational
packages of facies. Given the hydrocarbon potential of the Nullipore Formation, conventional
well logs of six boreholes and core analyses data from one of these wells (RF-B12) are used to identify
electrofacies zones of the Nullipore Formation. The Nullipore Formation has been subdivided into three
electrofacies zones (the Nullipore-I, Nullipore-II, and Nullipore-III) that are well-correlated with the three
depositional sequences. Results of petrographical studies and log analyses data have been employed in
volumetric calculations to estimate the amount of hydrocarbon-in-place and then the ultimate recovery
of the Nullipore reservoir. The volumetric calculations indicate that the total volume of oil-in-place is 371
MMSTB at 50% probability (P50), whereas the total recoverable oil is 148.5 MMSTB at P50. The volumetric
calculations for the Nullipore zones match the production data indicating a good simulation for the
reservoir productivity through the petrophysical parameters. Comparison of the volumetric calculations
of the oil and the cumulative production of the Ras Fanar Oil Field indicates remaining reserves of less
than 30% of the total recoverable oil. Therefore, the search for unconventional and/or deeper reservoirs at
other water contacts is recommended. |
