Low salinity water flooding is an emerging technology in the field of enhanced oil recovery in recent years. Laboratory investigations and field trials have been done for different reservoirs worldwide to evaluate the performance of this new technique. The majority of the published literature reported positive results for relatively heavy asphaltic rich crude oil. Present work investigates the potential of low salinity water flooding for light oil reservoirs.

The effect of brine salinity and composition on interfacial tension and wettability has been investigated experimentally using crude oil sample from an Indian crude oil reservoir. Interfacial tension between crude oil and different brine solutions were measured using Wilhelmy plate method. The effect of brine composition on wettability is accessed through contact angle measurements using a custom built goniometer on a quartz substrate. Brine solutions of different compositions were prepared by dissolving monovalent and divalent salts in deionized water. Crude oil has been well characterised for its chemical and physical properties including IR spectroscopy. Surface characteristics and composition of the quartz plate, used for contact angle measurements is determined using scanning electron microscopy and electron dispersive X-ray spectroscopy. All the experiments were done under a high-temperature condition which is close to most of the typical petroleum reservoirs. The results of this paper shows that reduction in brine salinity has a significant effect on both crude oil-water interfacial tension and reservoir wettability for light paraffinic oil reservoirs. The oil-water interfacial tension can be decreased with lowering brine salinity. Interfacial tension results also show that higher divalent ion concentration has no significant impact on interfacial tension reduction for paraffinic crude oil. It was observed from contact angle measurements that reduction of brine salinity can significantly affect reservoir wettability from oil wet to water wet condition. But, under extremely low salinity condition, this trend is reversed and become more oil wet. The interfacial tension is also observed to increase slightly at a very low ionic concentration.

In the literature, most of the low salinity investigations were performed on relatively heavy and medium gravity crude oil having significant resin and asphaltene content. Interaction of asphaltene and resin with ions at oil water interface is related to recovery improvement in most of the low salinity literature. But, this study shows that low salinity or smart water could be a potential EOR method for light oil reservoirs with more paraffinic content.

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