Integrated petrographical and petrophysical studies for reservoir characterization of the Middle Jurassic rocks at Ras El-Abd, Gulf of Suez, Egypt

Abstract

Acoustic velocity and petrophysical parameters of thirteen samples from the Middle Jurassic Ras El-Abd exposure, west Gulf of Suez, Egypt, have been measured and integrated with the petrographical analysis to evaluate the effect of diagenetic processes on the reservoir quality. The average compressional and shear wave velocities of dry (Vp dry) and saturated (Vp sat) sandstone rock samples are lower than those of carbonate samples. The diagenetic processes affected on the acoustic properties of the studied sandstone and carbonate rocks. The neomorphism and cementation processes caused an increase in the compressional and shear wave velocities and a decrease in the reservoir quality as recorded in biomicrite and argillaceous dolomitic quartz arenite microfacies, whereas the dissolution and leaching processes caused a decrease in the acoustic characteristics and an increase in the reservoir quality as represented by quartz arenite and ferruginous quartz wacke microfacies. In order to decrease the cost of acoustic analysis, the estimated empirical equations can be used for the prediction of compressional wave velocity of wet rock samples from the compressional wave velocity of dry rock samples, and the shear wave velocity of wet rock samples can be predicted from the shear wave velocity of dry rock samples. The correlation of the relative sea-level change for the studied section according to facies changes with the global fluctuation revealed that, the lower interval of Bajocian age is dominated by a fall in sea-level manifested by the deposition of quartz arenite microfacies and hence has a higher reservoir quality than the upper part of the succession.