Petrophysical and Petrographical Evaluation of Sandstone Reservoirs for Low-Salinity Waterflooding: A Case Study of the Kareem Sandstone Formation, Morgan Field, Gulf of Suez, Egypt

Abstract

Low-salinity waterflooding (LSWF) has emerged as a promising and environmentally sustainable enhanced oil recovery (EOR) technique, particularly for revitalizing mature oil fields. This study investigates the influence of reservoir heterogeneity on LSWF performance within the Kareem Sandstone Formation of the Morgan Field, located in the Gulf of Suez, Egypt. By employing advanced petrographical analyses—including thin-section (TS) imaging, scanning electron microscopy (SEM), and X-ray diffraction (XRD)—coupled with relative permeability measurements, this research aims to optimize recovery strategies and identify the key factors controlling the effectiveness of LSWF.The study analyzed four core samples using XRD and examined two samples through TS and SEM techniques. Findings revealed that the Kareem Sandstone Formation predominantly comprises quartz, dolomite, and feldspars, with kaolinite and smectite as the primary clay minerals, accompanied by minor amounts of illite and chlorite. Two distinct reservoir quality types were identified: one exhibiting good permeability (571 mD) and porosity (21%), and the other showing moderate permeability (249 mD) with slightly higher porosity (23%). Relative permeability analysis indicated that irreducible water saturation (Swi) averaged 19.0% at ambient conditions and 20.5% at reservoir conditions, while residual oil saturation (Sor) averaged 29.7%.The relative permeability curves indicated a trend toward water-wet conditions in certain reservoir samples, suggesting that LSWF could be a beneficial technique. By altering the rock surface to become more water-friendly, LSWF can significantly improve oil recovery. This research underscores the importance of integrating detailed mineralogical and petrophysical analyses to understand better the mechanisms of LSWF, particularly in heterogeneous sandstone reservoirs.