Effect of salinity degree of injected water on oil recovery from carbonate reservoir

Abstract

Water injection is considered the most successful and widespread secondary recovery method. Low salinity water injections is a well-established and proved technique for water flooding application in sandstone rocks to enhance the recovery efficiency; where the water salinity is adapted to a certain degree to extract the highest amount of oil from a reservoir. Reserve-estimation statistics show the significance of oil reserves in carbonate reservoirs, hence this work deals with the carbonate rocks where water flooding may fail due to many reasons, and the most common one is fractures existence in the carbonate rocks. This work applied the water injection for six carbonate (limestone) core samples from Belayim Formation of Middle Miocene age that extracted from an Egyptian offshore oil field in the Gulf of Suez. This carbonate facies is hard, vuggy, fragmented, dolomitic, and highly saturated with oil and considered a good reservoir. Relative permeability test was carried out to investigate the reservoir response in terms of recovery efficiency hence residual oil saturation, when flooding the reservoir with waters having different salinity ratios. Results showed an increase in recovery efficiency for all the tested samples, on applying the low salinity water injection, where all the relative permeability curves displayed wettability modification/alteration toward water wetness properties.