Anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores. Before performing core floods, the stability of nanoparticles at different salinities was tested using ζ potential and ultraviolet–visible (UV–vis) methods. While water recovered only 49% of the oil in the core flood experiments, 0.01% anatase structure solution recovered 80% of the oil after injecting two pore volumes at optimum conditions. To understand the mechanism responsible for improved recovery, contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution. Contact angle measurements showed that the rock wettability changed from oil-wet to water-wet conditions after treatment with nanoparticles. In 0.01% concentration, scanning electron microscopy (SEM) results showed homogeneous deposition of nanoparticles onto the core plug surface and a few nanorods with a diameter about 60 nm were observed. Energy-dispersive spectrometry (EDS) confirms diffusion of nanoparticles in porous media and uniform distribution. When the nanoparticle concentration was increased, more nanorods with the same diameter were composed, which resulted in plugging to occur. These results indicated the possibility of TiO2 application in enhanced oil recovery (EOR); however, more investigation is required to overcome multi-nanoparticle deposition onto pores.
Although application of nanoparticles in enhanced oil recovery has been reported, understanding the transport and retention of nanoparticles in the oilfield reservoir is still a crucial issue. In this research, behavior of low concentration of TiO 2 nanoparticles in core plug porous media and the mechanism of increasing oil recovery were investigated. Flooding test with a concentration of 0.01% TiO 2 nanoparticles showed improvement in sweeping heavy oil from 41% to 55%. Inductively coupled plasma results on the exiting effluent of the flooding test with a concentration of 0.05% TiO 2 nanoparticles showed the presence of only 0.5% of injected nanoparticles, which indicates high affinity of the nanoparticles for deposition in porous media. The total amount of deposited TiO 2 extracted from different cross sections of the core plug was consistent with the difference of injected and exited TiO 2 material. At the entrance side, the amount of deposited TiO 2 was high but decreased significantly in 0.1 cm depth, and reduces linearly versus distance. On the basis of surface area estimation of the core plug, only about 1% of the internal surface was deposited by nanoparticles. The viscosity, interfacial tension, and contact angle measurements showed that the main mechanism for increasing oil sweeping is changing the wettability of the rock surface from oil-wet to water-wet due to deposition of TiO 2 nanoparticles. The role of the low concentration nanofluid in rapidly displacing crude oil from the rock surface may be described by gradient pressure of nanoparticles in the three-phase contact wedge of oil, nanofluid, and rock surface.
In this paper, we discuss the synthesis and characterization of tungsten trioxide nanoparticles prepared by the arc discharge method in deionized (DI) water. The size and morphology of WO(3) nanoparticles prepared using different arc currents (25, 35 and 45 A) were studied. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) results indicate that at an arc current of 25 A, the size of the particles is about 30 nm, and this increases to 64 nm by increasing the arc current. This size increase caused a decrease of optical band gap from 2.9 to 2.6 eV. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) spectra demonstrate the formation of the WO(3) phase. Photodegradation of Rhodamine B shows that samples prepared at the lowest current have more photocatalytic activity due to having the smallest particle size and highest surface area. The results demonstrate the ability of the arc discharge method for direct formation of WO(3) nanoparticles in DI water medium.
We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been derived from the AFM data. Force displacement curves using the Derjaguin-Müller-Toporov (DMT) and the massless cantilever beam models yield a Young modulus of E(c) approximately 37, E(a) approximately 0.7 TPa and a Hamakar constant of approximately 3 x 10( - 18) J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated from the DFT outcomes approximately 0.82 TPa and the results were compared with the experiment. We found that the Young's modulus and the threshold shearing force are dependent on the direction of applied force and the values are different for zigzag edge and armchair edge GNRs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.