Petrophysical and microfacies analysis as a tool for reservoir rock typing and modeling: Rudeis Formation, off-shore October Oil Field, Sinai

Abstract

Petrographically, the Lower Miocene Rudeis reservoir rock samples in October oil field can be summed up into three reservoir rock types RRTs. The RRT1 samples are mostly calcareous to ferruginated sandstones, sometimes are fossiliferous, whereas the RRT2 and RRT3 samples are carbonate rocks of grainstone and packstone microfacies, respectively. Cementation by sparite and compaction are the most important porosity-reducing diagenetic factors, whereas dissolution and leaching out as well as fracturing are the most dominant porosity-enhancing factors. The petrophysical and reservoir quality studies include measuring density, porosity, permeability measurements as well as reservoir quality index (RQI), flow zone indicator (FZI) and reservoir potential index (RPI) calculations. The permeability-porosity plot is the key-factor for discriminating the petrophysical behaviour into these three rock reservoir types. Petrophysically, the studied sandstone RRT1 samples have the best storage capacity and reservoir quality (the RQI, FZI and the RPI indicate poor to very good reservoir quality), whereas the RRT3 samples have the least prospective properties (the RQI, FZI and the RPI indicates impervious reservoir quality). Based on the FZI values, the studied Rudeis Formation was discriminated into a number of hydraulic flow units (6 HFUs). HFU 5–6 are the best reservoir zones; they are assigned in the central parts of the studied area, whereas the least quality (HFU 1–3) was assigned to the south. In addition, the mercury injection capillary pressure tests (MICP) indicates that, the RRT1 samples are ranked as IV (fair) to VI (impervious) ranks, the RRT2 as V (poor) to VI, whereas the RRT3 samples are impervious samples. Wettability of the studied RRT1 samples is mostly neutral.