Abstract
Characterization of emulsion formation (amount and droplet size) in the brine–oil–nanoparticle systems as a function of varying size of nanoparticles and modified brine salinity is presented. Different brines were used with a range from zero salinity for deionized water (DIW) to synthetic seawater (SSW), mimicking the salinity of North Sea water. Brines (FW1 and FW2) representing the composition of formation water obtained from different production wells (North Sea) were also used. Two model oils (decane (D) and hexane–hexadecane (HH) mixture of 1:1 vol. ratio) and a sample of North Sea crude oil (NSCO) were used. CaCO3 nanoparticles of three different sizes of 15-40, 50, and 90 nm were used. Nanoparticles characterization was performed with Transmission Electron Microscopy (TEM). A commercially available sonication equipment, Branson Sonifier® SFX250, was employed for emulsion formation in brine–oil–nanoparticles systems. All the experiments were performed at room temperature for the same experimental conditions of 5 minutes of ultrasonic processing by using a 6.5 mm tapered microtip (sonication probe) with an output power of 30 W. Emulsion characterization (emulsion droplet size) was performed with an optical microscope (Axio Scope.A1).
The effect of size of CaCO3 nanoparticles and brine salinity on emulsion formation was investigated for different brine–oil systems. The results showed that the emulsion formation in brine–model oil (D and HH) systems was an inverse function of the size of nanoparticles i.e., a large amount of emulsion formation was observed for the smaller sized nanoparticles and vice versa. Emulsion characterization for these systems showed that the emulsion droplet size increased with an increase in size of the nanoparticles. The brine salinity also showed a significant effect on emulsion formation in brine–model oil systems i.e., a decrease in brine salinity showed an increase in emulsion formation and correspondingly smaller emulsion droplet sizes. However, the brine salinity did not affect the emulsion formation and emulsion droplet size for 15-40 nm nanoparticles. Contrary to the brine–model oil results, the results of brine–NSCO systems neither showed any dependence on the size of nanoparticles nor on the brine salinity. This might be due to the presence of polar fractions (polar acids and polar bases) in the crude oil.
The characterization study presented in this paper can provide a foundation for future development of calcite nanoparticle based EOR applications in the carbonate reservoirs.
