The mechanism of oil viscosity reduction with the addition of graphene nanoparticles

Understanding the interaction mechanisms between graphene nanoparticles (GNPs) and oil molecules is crucial for successful oil recovery. Numerous studies have shown that nanofluids (NF), especially nanofluids from the graphene family (GNF), are suitable candidates for enhanced oil recovery in various reservoirs. Increased oil recovery from nanofluid injection is attributed to changes in wettability, decreases in interfacial tension and changes in viscosity. Therefore, knowing the mechanisms affecting GNF viscosity is an urgent task of modern science, both fundamental and applied. In this paper, we conducted a comprehensive study of the molecular interaction between GNPs and hydrocarbon molecules of oil in order to establish the mechanisms affecting the viscosity of nanofluids. This paper presents the results of a study of the rheological properties of oil with different content of graphene nanoparticles in it. At low concentrations of GNP a decrease in the dynamic viscosity of the base fluid by 10%-17% was observed. It is also shown that the viscosity is affected not only by the concentration, but also by the temperature. Thus, for the concentration of graphene nanoparticles wt = 0.5 x 10(-3)% and temperature T = 50 degrees C, a maximum viscosity reduction of 17% is observed. When the concentration of graphene nanoparticles increases from wt = 5 x 10(-3)% and more, the viscosity profile of GNF does not differ from that of most NF. The paper presents the methodology and describes the experimental setup to study the behavior of nanoparticles while moving in the flow of a carrier fluid. Based on this technique, including computer simulation and observation of self-assembly of GNP and hydrocarbon molecules, using a specially designed setup, a mechanism is proposed which explains the decrease in nanofluid viscosity at low concentrations of nanoparticles. The mechanism of GNF viscosity reduction, where the base fluid (BF) is oil, is related to the self-assembly of GNP in the carrier fluid flow. However, according to the results of experiments and analysis of the viscosity mechanism of GNF, the viscosity reduction for water based GNF, with increasing concentration of nanoparticles, is not possible. The findings of this study can help for better understand the rheological properties of GNF, which opens up new possibilities for the commercial use of NF in the petroleum and energy industries. (C) 2022 Elsevier B.V. All rights reserved.