Case study: the impact of Low Salinity Waterflooding on Sandstone Reservoirs at Egypt’s Western Desert

Abstract

Surface chemistry has a great effect in enhancing oil recovery (EOR). For oil-wet sandstone reservoirs, low salinity waterflooding (LSWF) is effective as it can alter rock wettability and reduce the oil/water interfacial tension. LSWF application is related to the rock’s clay content and type. Clay hydrocarbon bonding can be formed through many mechanisms such as van deer forces and ionic bridge. LSWF effect is to weaken these bonds through two main mechanisms, Double Layer Expansion (DLE) and Multicomponent Ionic Exchange (MIE). This research figure out the impact of LSWF application through a comparsion between two fields (S & D), in Egypt’s Western Desert, which have depleted strongly oil-wet reservoirs with similar rock & fluid Properties. Field (S) is flooded by low salinity water (LSW), while field (D) is flooded by high salinity water (HSW). Fortunately, the LSWF application was with no extra desalination cost as the water source for field (S) flooding is a LSW aquifer zone, which has a salinity +/- 5000 ppm as total dissolved solids (TDS). Water Susceptibility for Field (S) rock showed good compatibility between the injected LSW, formation water and rock minerals. XRD and SEM for field (S) indicate calcareous cementation with detrital clays content around 5% which is mainly kaolinite. This composition helps to activate the LSWF effect. For field (S), the estimated ultimate recovery (EUR) is 46%, while EUR for field (D) is 39%. One of the main causes of this increase in field (S) is the successful LSWF application.