Flow Unit Characterization in Pliocene Reservoirs: Derived from Core Analysis, Capillary Pressure and Wire Line Logs, Offshore Nile Delta, Egypt

By

Anwar Naiem Mohamed¹, Mohamed Tarek A. El-Latif², Mohamed Reda Osman²

 (1) BP, Cairo, Egypt (2) BP Egypt Gas Business Unit

 Abstract

Recent deep-water Pliocene discoveries in the Offshore Nile Delta established the Pliocene sequence as a primary hydrocarbon potential target. Core analysis and wire line data from recent slope channel discoveries in the North Alexandria Concession provide a typical example of reservoir facies and saturations within these trends.

Three major flow units are present 1) channelized high quality reservoirs 2) low permeability debris flows 3) thinly laminated turbidities. MDT pressure and samples in addition to well test data show that the thinly laminated facies contains significant gas pay. Conventional wire line logs consistently underestimate gas volumes or miss the pay zones entirely, resulting in a classic “low resistivity” pay identification problem. In addition, seismic imaging of these laminar zones is difficult.

Detailed core analysis in conjunction with Dipmeter Image Analysis and NMR Data show that thinly laminated reservoirs exhibit a wide variance of gas saturations from high quality multi Darcy reservoirs to seals. The formation pressure data to date, suggests that laminar seals are laterally ineffective, with all zones communicating vertically. Thin sections and x-ray diffraction data show thin and high quality reservoir laminations even in micro scale, with a strong preferential horizontal permeability and less vertical permeability.

The wide variance in rock type makes accurate quantification of Sw difficult in the low resistivity horizons, but the overall volume of potential pay is both recognizable on FMI and CMR logs, and can be quantified, giving substantial potential upside in each new slope turbidities discovery made.