Electrical properties of sedimentary microfacies and depositional environment deduced from core analysis of the syn-rift sediments, Northwestern shore of Gulf of Suez, Egypt

Abstract

The present work is based mainly on core rock samples investigation of CSS-38 well, northwest of Gulf of Suez, Egypt. The cores cover the whole the South Gharib Formation (upper Miocene). The stratigraphic succession of the Gulf of Suez includes three mega units, recorded from old to young as pre-rift, syn-rift, and post-rift sediments. The syn-rift sediments from old to young are Nukhul, Rudies, Kareem, Belayim Equivalent, South Gharib, and Zeit. The core samples reveal that South Gharib Formation is not a good reservoir. It consists of sulphate-rich beds with few carbonates intercalation, laminated dolomitic limestone and marly limestone. Patchy oil staining is detected in the thin streaks and basal laminated dolomitic limestone. The microfacies are found to be evaporites, carbonates, calcareous marl, and calcareous claystone. Evaporites microfacies are considered the most frequent microfacies. Gypsum and anhydrite are generally represented by nearly equal distribution with parallel variation in content. The core samples differentiated South Gharib Formation into seven zones of depositional environment; they are arranged from base to top as shallow sub-tidal, shallow lagoonal, intertidal, shallow lagoonal, intertidal, shallow lagoonal, and supra-tidal Sabkha cycles. Some samples from South Gharib Formation were measured electrically. We will try to highlight interrelations between electrical (conductivity, permittivity, and impedance) and petrophysical properties with petrography and mineral composition. Electrical properties were measured with a frequency range from 10 Hz to 100 kHz. The dielectric constant decreases with increasing frequency and increases with increasing conductor content (up to percolation threshold). The conductivity increases with the increase in conductor content and with increasing frequency. Many parameters can combine to affect electrical properties. The present research is a trial to relate the surface to subsurface measurements.