Impact of nanoparticles on the CO2-brine interfacial tension at high pressure and temperature

Hypothesis: Nanofluid flooding has been identified as a promising method for enhanced oil recovery (EOR) and improved Carbon geo-sequestration (CGS). However, it is unclear how nanoparticles (NPs) influence the CO2-brine interfacial tension (gamma), which is a key parameter in pore-to reservoirs-scale fluid dynamics, and consequently project success. The effects of pressure, temperature, salinity, and NPs concentration on CO2-silica (hydrophilic or hydrophobic) nanofluid gamma was thus systematically investigated to understand the influence of nanofluid flooding on CO2 geo-storage. Experiments: Pendant drop method was used to measure CO2/nanofluid gamma at carbon storage conditions using high pressure-high temperature optical cell. Findings: CO2/nanofluid gamma was increased with temperature and decreased with increased pressure which is consistent with CO2/water gamma. The hydrophilicity of NPs was the major factor; hydrophobic silica NPs significantly reduced gamma at all investigated pressures and temperatures while hydrophilic NPs showed only minor influence on gamma. Further, increased salinity which increased gamma can also eliminate the influence of NPs on CO2/nanofluid gamma. Hence, CO2/brine gamma has low, but, reasonable values (higher than 20 mN/m) at carbon storage conditions even with the presence of hydrophilic NPs, therefore, CO2 storage can be considered in oil reservoirs after flooding with hydrophilic nanofluid. The findings of this study provide new insights into nanofluids applications for enhanced oil recovery and carbon geosequestration projects. (C) 2018 Elsevier Inc. All rights reserved.