Petrophysical analysis of the messinian Qawasim Formation in El Tamad Field (Nile Delta)

Abstract

The onshore Nile Delta has shown promise in oil and gas production in Egypt. However, exploration activities in the past decade indicated conspicuous spatial changes in the quality and geometry of reservoirs. Therefore, petrophysical traits of the productive horizons must be monitored continuously. Based on detailed logging data of five wells, the spatial changes in the reservoir quality and geometry of the Messinian (Late Miocene) Qawasim Formation in El Tamad Field (Northeast Nile delta) was reevaluated. All integrated petrophysical analyses (i.e. lithology, porosity, net pay thickness, shale volume, water saturation, and hydrocarbon saturation) indicated a high spatial variability, where up to 12 different zones have been identified in the Qawasim Formation. Indeed, the Qawasim Zone 2 has the highest potentiality of hydrocarbons (i.e. Main Pay Zone) with good porosity (19.1–27.8%), low shale volume (14.9–22.1%), and low water saturation (22.1–44.4%). The constructed cross-plots (i.e. Neutron-Sonic, Neutron-Bulk Density, and M-N plots) showed that the reservoir is composed mainly of quartz arenite. The dia-porosity cross plot (density porosity ‘ØD’-neutron porosity ‘ØN’) indicated that the pore spaces are interpenetrated with dispersed shale of minor laminated types. To identify the free water-level and the contact with gas or oil, the hydrostatic pressure gradient using pressure-depth plot was implemented. The gas gradient ranges from 0.07 to 0.08 psi/ft with an average 0.075 psi/ft, while the oil pressure gradient ranges from 0.26 to 0.24 psi/ft with an average 0.25 psi/ft and the water gradient is about 0.45 psi/ft. Future exploration and production in the area should take in account that the Qawasim Formation represents a good reservoir but with marked spatial heterogeneity in the reservoir quality and geometry.