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Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding.

ABSTRACT: Laboratory experiments and field trials have shown that oil recovery from carbonate reservoirs can be increased by modifying the brine composition injected during recovery in a process termed controlled salinity water-flooding (CSW). However, CSW remains poorly understood and there is no method to predict the optimum CSW composition. This work demonstrates for the first time that improved oil recovery (IOR) during CSW is strongly correlated to changes in zeta potential at both the mineral-water and oil-water interfaces. We report experiments in which IOR during CSW occurs only when the change in brine composition induces a repulsive electrostatic force between the oil-brine and mineral-brine interfaces. The polarity of the zeta potential at both interfaces must be determined when designing the optimum CSW composition. A new experimental method is presented that allows this. Results also show for the first time that the zeta potential at the oil-water interface may be positive at conditions relevant to carbonate reservoirs. A key challenge for any model of CSW is to explain why IOR is not always observed. Here we suggest that failures using the conventional (dilution) approach to CSW may have been caused by a positively charged oil-water interface that had not been identified.

SUBMITTER: Jackson MD

PROVIDER: S-EPMC5120358 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding.

Jackson Matthew D MD Al-Mahrouqi Dawoud D Vinogradov Jan J

Scientific reports 20161123

Laboratory experiments and field trials have shown that oil recovery from carbonate reservoirs can be increased by modifying the brine composition injected during recovery in a process termed controlled salinity water-flooding (CSW). However, CSW remains poorly understood and there is no method to predict the optimum CSW composition. This work demonstrates for the first time that improved oil recovery (IOR) during CSW is strongly correlated to changes in zeta potential at both the mineral-water ...[more]

PMID: 27876833

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Project description:Low salinity waterflooding (low salinity-EOR) has attracted great interest from many giant oil producers and is currently under trial in some of the oil fields of the United States, Middle Eastern countries, and North Sea reservoirs. Most of the reported studies on this process were carried out for medium to relatively heavy oil with significant polar contents. In this work, we have investigated low salinity waterflooding performance for light paraffinic crude oil with a low acid number. This study has been performed using crude oil from an Indian offshore oilfield and Indian offshore seawater. Oil recovery efficiencies of seawater and its diluted versions (low salinity seawater) were evaluated through core-flooding experiments performed on a silica sand pack containing small amounts (2 wt %) of bentonite clay saturated with crude oil. Interfacial tension and wettability studies were performed to understand the associated low salinity effects on the crude oil/brine/rock properties. Effluent brine produced during the flooding experiments was also analyzed to obtain a clearer insight into the low salinity-enhanced oil recovery (EOR) mechanism. The results showed that injection of low salinity seawater can significantly increase the waterflood recovery in comparison with high salinity seawater injection. Interfacial tension and contact angle studies revealed that there is an optimum dilution level at which the interfacial tension and wettability are the most favorable for enhanced oil recovery even in the case of light paraffinic crude. These results are in line with the results obtained from the core-flooding experiments. The possible reason behind recovery improvement based on the interfacial tension and wettability studies in conjugation with the effluent brine analysis has been discussed in detail. In this study, we have observed that the enhanced oil recovery efficiency could be achieved by applying low salinity seawater flooding even in the case of light paraffinic oil with a low acid number.

Dataset Information

Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding.

Publications

Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding.

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