Abstract
The main objective of this study is to investigate the impact of the depositional and diagenetic processes on the petrophysical and mechanical properties of the Lower Miocene Moghra Formation sandstones exposed at the Qattara Depression, Northwestern Desert, Egypt. We conducted several petrophysical and mechanical investigations on a large number of core samples collected from the study area to determine their petrophysical and mechanical characteristics. Results of petrographical, scanning electron microscope (SEM), and the X-ray diffraction (XRD) analyses revealed that the studied sandstones are composed essentially of quartzarenites with minor limestone and shale intercalations and can be grouped into three sedimentary lithofacies: fossiliferous dolomitic quartzarenites, ferruginous quartzarenites and calcareous quartz arenite. The main diagenetic processes encountered in the Moghra sandstones are compaction, cementation, and dissolution. These processes significantly affected the porosity and influenced the petrophysical and mechanical parameters of the studied sandstones. The Moghra sandstones have average values of 14.51%, 2.24 g/cm(3), 22.38 mD, 45.77%, and 3377 m/s, for porosity (phi), bulk density (rho(b)), permeability (K), irreducible water saturation (S-wirr), and the P- wave velocity (Vp), respectively. In addition, these rocks have average values of 83.98 MPa, 5.97 MPa, and 34.42, for the unconfined compressive strength (UCSdry), the point load strength index (IS50), and the Schmidt hammer number (SHN), respectively. Significant relationships, with moderate/high correlation coefficients, have been obtained between the investigated parameters of the studied sandstones. The studied sandstones, however, showed no clustering of their petrophysical and mechanical properties based on their facies type. The present results indicate that both porosity and bulk density, which are in turn the products of the depositional and diagenetic history of the investigated rocks, are major parameters controlling the other petrophysical and mechanical properties of the studied rocks.