|dc.description.abstract||Over the past decade, nanoparticles (NPs) have been tested to assist waterflooding (WF) for enhanced oil recovery (EOR) due to their superior physical and chemical properties. Majority of the previous studies used silicon oxides (SiO2) coated with polyethylene glycol or silane and other metallic oxides as NPs. In this study, a nanofluid (NF) was first characterized in terms of its bulk and interfacial properties, which comprised NPs dispersed in an aqueous phase. Second, the NP loss in a porous medium because of adsorption was measured. Third, a series of NP-assisted WF tests were conducted to measure the heavy oil recovery factors and identify the best type and optimum concentration of NPs for enhanced heavy oil recovery in a heavy oil reservoir.
Four types of commercial metallic oxide NPs for EOR (Nano-EOR) were used: uncoated hydrophilic 25 wt.% SiO2 NP solution and 20 wt.% Al2O3 NP solution, SiO2 nanopowders coated with 2 wt.% dimethoxydiphenylsilane (KH220-silane) and SiO2 nanopowders coated with 3–4 wt.% aminopropyltriethoxysilane (KH550-silane). A NF, which was made of each type of NP solution or nanopowders and a deionized water (DIW)/brine, was characterized in terms of its density, viscosity, pH, and specific electrical conductivity, surface tension (ST) of the DIW/brine/NF and air, and interfacial tension (IFT) between a given heavy oil and DIW/brine/NF. First, the densities and viscosities of the DIW/brine/NFs were measured. Second, the pH values and the specific electrical conductivities of the DIW/brine/NFs were measured. Third, the STs of the DIW/brine/NFs and the air, as well as the IFTs between the Manatoken heavy oil and DIW/brine/NFs, were measured. Fourth, a series of static adsorption tests were undertaken to determine the NP adsorption onto the Ottawa sand grains. Finally, a total of twelve NP-assisted WF tests were conducted in a sandpacked coreholder to measure the heavy oil recovery factors (RFs) under different test conditions.
Dispersion of the NPs did not remarkably increase the densities of the NFs. As uncoated SiO2 NPs at 0.02 wt.% and 0.06 wt.% concentrations were dispersed in the brine with 1.00 wt.% NaCl (NF1 and NF2), nevertheless, the NF viscosity was increased from 3.38 cP to 4.91 cP, respectively. The pH value was 7.75 for 0.06 wt.% SiO2 NPs with KH220-silane coating in the brine with 4.00 wt.% NaCl (NF3), compared to 7.05 for the DIW. The measured specific electrical conductivity was increased from 41.3 μS/cm for the DIW to 62,810.0 μS/cm for 0.06 wt.% Al2O3 NPs in the brine with 4.00 wt.% NaCl (NF4). The measured STs indicated that the STs of the DIW/brine/NFs and air were increased from 70.91 mJ/m2 for the DIW to 93.13 mJ/m2 for NF4. The measured IFTs between the Manatoken heavy oil and DIW/brine/NFs exhibited the lowest value of 15.14 mJ/m2 for 0.04 wt.% SiO2 NPs with KH220-silane coating in the brine with 4.00 wt.% NaCl (NF5). In addition, the static adsorption test data indicated the highest NP adsorption of 1.06 mg/g onto the Ottawa sand grains for NF4.
Finally, the highest total heavy oil RF of 61.64% was achieved for NF5 in the NP-assisted waterflooding (NPWF), WF, and extended NPWF in comparison with 46.31% obtained for NF5 in WF, NPWF, and extended WF. The optimum NP concentration for the highest enhanced heavy oil RF was approximately 0.04 wt.%. Below the optimum NP concentration, the oil RF was lower because of weaker interactions between the NPs and the reservoir fluids. Above the optimum NP concentration, the oil RF was decreased possibly because of increased NP aggregation and adsorption.||en_US