Impact of amine@ZnO/CNT and fatty acid@ZnO/CNT as hydrophilic functionalized nanocomposites on reduction of heavy oil viscosity

Abstract

One of the important features of heavy oil reservoirs is their high viscosity, which reduces the recovery factor of oil in these reservoirs. Thermal methods have traditionally been used for viscosity reduction in enhanced recovery process (EOR). However, these methods are not justifiable due to the high cost of steam energy production, the production of coke in the process, steam injection and environmental problems. Viscosity can be dramatically reduced with the help of nanoparticles, without using limited and controlled heat. In this study, ZnO/CNT nanocomposites, which have been made hydrophilic by surface modification operations, have been used as aqueous based nanofluids in enhanced recovery process. A heavy oil with viscosity of 402 cP at 80 °C was used in viscosity reduction tests. The results showed that the viscosity reduction of heavy oil from 402 cP at 80 °C to 74.90 and 16.23 cP at 80 °C is possible using reference nanofluids based on ZnO and CNT nanoparticles, respectively. In the next step, the effect of four parameters of concentration, salinity, pH and mixing intensity on the heavy oil viscosity were investigated to evaluate the performance of the nanocomposite. Amine surface modified nanocomposite samples fluidized in distilled water and fatty acid surface modified nanocomposites fluidized in seawater functioned better and reduced the viscosity to 33.74 and 26.08 cP at 80 °C, respectively. The effect of pH on viscosity was negligible, which is a positive feature of these nanocomposites. The mixing process of oil and nanofluid on viscosity reduction was shown to have much more effect on viscosity reduction in comparison to non-mixing process. The greatest reduction of viscosity without mixing was measured to be 261.26 cP at 80 °C using fatty acid@ZnO/CNT nanofluid, which is almost ten times more than the condition that mixing was performed ideally.