Petrophysical and Mechanical Evaluation of the Moghra Sandstones, Qattara Depression, North Western Desert, Egypt

Abstract

In the present study, we conduct a number of petrophysical and geomechanical investigations on a large number of sandstone core samples collected from the Lower Miocene Moghra Formation exposed at Qattara Depression, North Western Desert, Egypt to determine their reservoir characteristics and to investigate the effect of the provenance and digenetic processes on their petrophysical and geomechanical characteristics. Results of petrographical, scanning electron microscope (SEM) and the X-ray diffraction (XRD) analyses show that the studied sandstones are composed mainly of quartzarenites with little limestone and shale interbeddings and can be categorized into three main sedimentary microfacies: fossiliferous dolomitic quartzarenites, ferruginous quartzarenites and calcareous quartz arenite. The mainly-recognized diagenetic processes that prevailed during the post-depositional history of the Moghra sandstones are compaction, cementation, and dissolution. These processes impacted the porosity and influenced the petrophysical and geomechanical parameters of the studied sandstones. The Moghra sandstones possess average values of 14.74%, 2.21 g/cc, 2.76 g/cc, 23.02 mD, 49.44%, and 3341.17 m/s, for porosity (∅), bulk (ρb) and grain (ρg) densities, permeability (K), irreducible water saturation (SWirr), and the P wave velocity (Vp), respectively. In addition, these rocks have average values of 81.92 MPa, 5.84 MPa, and 58 for the unconfined compressive strength (UCSdry), the point load strength index (IS50) and the Schmidt hammer number (SHV) respectively. Significant relationships, with high correlation coefficients, between the investigated parameters have been obtained for the studied sandstones. The results indicate that both porosity and bulk density are the major parameters which control other petrophysical and geomechanical parameters