Integrated geological and petrophysical characterization of oligocene deep marine unconventional poor to tight sandstone gas reservoir

Abstract

The present study aims to evaluate, discriminate and delineate the geological and petrophysical situation of Oligocene reservoir wells at Salamat-1 and Atoll-1 in North Damietta offshore concession in the Mediterranean Sea. It deals with a combined interpretation of the core analysis (density, porosity, permeability and mercury injection capillary pressure ‘MICP’) and petrography data (thin sections, scanning electron microscope and X-ray diffraction) as well as well log (gamma ray, density, neutron, micro spherical logs ‘MSFL’, shallow and deep resistivity, and Modular Formation Dynamic Tester logs) and the subsurface geologic data, as well as some available seismic sections to clarify the geological and the petrophysical characterization of the Oligocene unconventional tight sandstone gas reservoir, Salamat structure, North Damietta offshore, Mediterranean Sea, Egypt. Petrophysically, the studied sandstone core samples can be summed up into two reservoir rock types (RRT), where poor reservoir quality is assigned to one group while the other is characterized by tight reservoir properties. These two RRTs are discriminated into four microfacies, two arenite groups and two wacke groups. Filling the pore spaces with detrital clays are the most important reservoir quality-reducing factors. The seismic data indicates that the studied area is composed of Rupelian-Chattian multi-channel system located off shore with many sand channels distributed in the area. The Lower and Upper Chattian sand channels comprise the most important reservoir bodies in Atoll-1 well to the northeast of the study are gas-bearing bodies, whereas the Rupelian sand channels to the northwest at Salamat-1 well are the most important gas-bearing channels. Integration between the available core and well log data indicated that the best storage and flow capacity are assigned to the other water-bearing sand channels rather the gas-bearing channels in both Salamat-1 and Atoll-1 wells. • The Rupelian-Chattian multi-channel sandstones are the target of this study. • Delineate the geological and petrophysical situation of Oligocene clastic reservoirs. • Petrophysically, two reservoir rock types can be assigned in the studied sequence. • Petrographically, the studied samples are discriminated into four microfacies. • Filling the pore spaces with detrital clays is the main reservoir quality-reducing factor.