عنوان مقاله [English]
Injection of nanofluids in oil reservoirs is one of the new methods for increasing oil recovery. The stability of these fluids in reservoir conditions and negligible formation damage, along with the significant increase in oil recovery are the factors which influence the selection of suitable nanofluids for increasing oil recovery in harsh reservoir condition. In this study, the efficiency of three nanostructures: nano-gamma-alumina, iron(III) oxide and silica with concentrations of 200, 500 and 600 ppm and with two different mixture ratios of formation water and reservoir injected water in a brine with a salinity of 106000 ppm to 234000 ppm, and a temperature of 90°C in oil extraction from oil-wet, media has been studied. In this part of the study, by conducting two-dimensional flow experiments in a glass micromodel at ambient temperature and atmospheric pressure, the displacement of oil by injecting fluid was studied, and the mechanisms of the performance of nanofluids were investigated for enhancing oil recovery. Zeta potential of the fluids was measured for the reservoir pressure and temperature (T= 90°C, p=2700 psi) to insure stability of the fluids. The results of these experiments showed that injection of all three nanofluids can enhance oil recovery up to 20% in comparison to that for the injection of brine. The highest amount of recovery was recorded for alumina nanostructure and then for iron oxide and silica respectively. Due to the slight change in the viscosity of nanofluids compared to water injected, and also the negligible change in the interfacial tension of the aqueous-oil phase for alumina and silica nanofluids, and the results of static tests for determining the contact angle, the mechanism change of wettability to water wet condition seems to be the dominant mechanism for alumina and silica nanofluids for this increase in oil recovery. Considering the slight change of iron (III) oxide nanofluid and results of pendant drop test for interfacial tension measurement of the nanofluid, the reduction of interfacial tension of water-oil phase for iron (III) oxide nanofluid may be reported as the dominant mechanism of enhanced recovery. The formation process of emulsion with iron (III) oxide nanofluid and oil is a confirmation of this mechanism for iron (III) oxide nanofluid.