Abstract
Abstract Modification of injection water salinity to improve oil recovery is not a new idea and the process has been investigated as far back as the 70's prior to the use of other chemical processes to improve oil recovery. In practice in planning water flooding project oil companies focused only on the compatibility of injection water and formation water issue to eliminate any possibility of formation damage. Many investigators recently had focused their research on the role of water salinity alteration to improve oil recovery. A number of possible mechanisms concerning alteration of water flooding salinity have been proposed in the literature. This project describes an experimental investigation of contact angle changes as function of time, and water flood performance using limestone and sand stone rocks for various injection brines. Carbonate rocks, sandstone rocks obtrained from a Libyan oil reservoir, high salinity water, sea water, low salinity water, and water contains different sulfate concentrations were employed in this study. The results of this research will shed more light on the mechanism of modified salinity flooding (MSFTM) and will help operating companies to better plan water flooding process. Introduction Water flooding has been used for many years to improve recovery from oil reservoirs. In the past, no attention has been given to the effect of the water composition and/or concentration on the possibility of increased oil recovery by alteration of salinity type and concentration. Historically the engineering design of water flooding focused only on avoiding formation damage by making sure no interaction between injected brine and indigenous brine. Morrow et al. (1996) concluded that alteration of brine composition of injected water can result in optimization of oil recovery. Tang and Morrow 1999; and McGuire et al. 2005, investigated further the effect of salinity on oil recovery and they have proved that decreasing brine salinity can improve oil recovery. Jerauld et al. 2008 indicated that more than 20 core floods using low salinity of sandstone reservoirs at reservoir conditions and at secondary and tertiary modes has been reported in the literature. Results of experimental work demonstrated an improvement of recovery efficiency due to low salinity by 5 to 38% and that manifested by reduction of residual oil saturation by 3 to 17% pore volume. Nasralla et al. 2011, indicated that injection of deionized water in the secondary mode resulted in a significant improvement in oil recovery compared to seawater. Different hypothesis have been introduced to explain the improvement in oil recovery by low salinity water injection. These include interfacial tension reduction, wettability alteration, change in pH (increase) resulting in in-situ saponification, emulsion formation, and clay migration.
Published Version
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