Inject water into an oil-bearing reservoir commonly known as waterflooding was introduced more than a century ago and since then it has been one of the most widely applied for displacing and producing incremental oil. Waterflooding has been extensively applied in the Danish part of the North Sea as a secondary recovery method (maintaining or enhancing reservoir pressure), while the performance of the system can be considerably improved. Advanced techniques can be developed and tested to apply as a tertiary recovery method (advanced technique). Several enhanced oil recovery (EOR) methods have been introduced to improve the performance of the system. Modified or controlled salinity waterflooding has been considered as the potential technique due to its high efficiency in displacing light-to-medium gravity crude oil, ease of injection into oil-bearing formations, reducing environmental footprint, availability and affordability of water, and lower capital and operating costs involved. The latter benefits lead to favourable economics compared to other EOR methods. It is considered that the injection of modified salinity has led to changes in calcite-brine-oil interactions which result in increasing oil recovery during the injection of seawater in the Ekofisk chalk. Recently, the experiments reported that the mechanism of modified salinity waterflooding is sensitive to temperature and a high temperature (above 70 °C) is a favourable condition.
In carbonates, particularly chalk, despite the substantial interest in the application of modified salinity waterflooding, the contribution of individual parameters (temperature, pressure, mineral surface, oil composition, and brine chemistry, including pH and ionic composition) on wettability alteration, which leads to additional oil production, has not quantified in-depth. And yet it is not clear how the impact of these parameters at the small-scale (mm) manifest themselves at the core (cm) or field (m) -scales. In this study, we plan to answer the following questions:
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How much does the lower temperature of the injection water reduce the recovery of oil?
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What are the technical and economic environmental impacts of the injection of hot water?
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Sweep and recovery: Interplay of modified salinity and temperature variation and heterogeneity