No abstract

Recently, nano-EOR has emerged as a new frontier for improved and enhanced oil recovery (IOR & EOR). Despite their benefits, the nanoparticles tend to agglomerate at reservoir conditions which cause their detachment from the oil/water interface, and are consequently retained rather than transported through a porous medium. Dielectric nanoparticles including ZnO have been proposed to be a good replacement for EOR due to their high melting point and thermal properties. But more importantly, these particles can be polarized under electromagnetic (EM) irradiation, which provides an innovative smart Nano-EOR process denoted as EM-Assisted Nano-EOR. In this study, parameters involved in the oil recovery mechanism under EM waves, such as reducing mobility ratio, lowering interfacial tensions (IFT) and altering wettability were investigated. Two-phase displacement experiments were performed in sandpacks under the water-wet condition at 95°C, with permeability in the range of 265–300 mD. A crude oil from Tapis oil field was employed; while ZnO nanofluids of two different particle sizes (55.7 and 117.1 nm) were prepared using 0.1 wt. % nanoparticles that dispersed into brine (3 wt. % NaCl) along with SDBS as a dispersant. In each flooding scheme, three injection sequential scenarios have been conducted: (i) brine flooding as a secondary process, (ii) surfactant/nano/EM-assisted nano flooding, and (iii) second brine flooding to flush nanoparticles. Compare with surfactant flooding (2% original oil in place/OOIP) as tertiary recovery, nano flooding almost reaches 8.5–10.2% of OOIP. On the other hand, EM-assisted nano flooding provides an incremental oil recovery of approximately 9–10.4% of OOIP. By evaluating the contact angle and interfacial tension, it was established that the degree of IFT reduction plays a governing role in the oil displacement mechanism via nano-EOR, compare to mobility ratio. These results reveal a promising way to employ water-based ZnO nanofluid for enhanced oil recovery purposes at a relatively high reservoir temperature.

Untreated nanoparticles possess huge surface areas compared to their mass, resulting in strong inter-particle interactions in saline water. This induces a strong tendency of particles' agglomeration, rapid sedimentation and consequently reduced the mobility of nanoparticles in the aquatic environment, which ultimately lowering the effective viscosity of the nano system. This study aimed to investigate the effect of stabilizers on the stability of dielectric nanofluid, to provide a better electrorheological characteristic for Nano-EOR purposes. In this research, zinc oxide (ZnO) was employed as dielectric nanoparticles under various nanoparticles concentration (0.1, 0.05, 0.01 wt. %). Anionic surfactants (SDS, SDBS, and Oleic acid) were compared in an attempt to prepare the homogeneous dispersions with long-term stability at high temperature (~ 95°C). The laboratory experiments were designed to evaluate the sedimentation behavior of nanoparticles using visualization method; whereas UV-vis spectrophotometry was employed to quantitatively characterize the stability of the nanoparticle dispersions. Further, dynamic light scattering (DLS) were also used to determine the size distribution of dispersed nanoparticles. The stabilized nanofluids were then subjected for measuring of electrorheological behavior using a rotating viscometer attached to a custom-built solenoid coil. From the experimental results, it is concluded that the most stable aqueous dispersion of ZnO nanoparticles is obtained at 0.1 wt. % with the aid of 0.025 wt. % SDBS under the conditions of 60 min of ultrasonication, adjusted at the pH value of 2. The ZnO/SDBS dispersion having a hydrodynamic size of 240.9 nm exhibits extreme stability at high temperature of 95°C, with the supernatant ZnO concentration decreasing only 19% compared with a decrease of 100% for the bare ZnO/Brine system. The rheological measurements indicated that all the nanofluids exhibit pseudoplastic (shear thinning) behavior. While the 0.1 wt. % ZnO/SDBS dispersion provide an enhancement in the relative viscosity of nanofluid up to 11% compared to brine as a basefluid, indicating the role of stability to achieve an electrorheological effect by activating dielectric ZnO nanoparticles. Additionally, the viscosity ZnO nanofluid increased with the increase of particle concentration under an applied field, which shows the strong dependence of viscosity on particle loading. The combined treatment with the surfactant, pH and ultrasonication is recommended to enhance the electrorheological characteristics of ZnO nanofluid. Hence, the mobility of a stabilized nanofluid can be efficiently controlled by regulating the applied field for EOR purposes.

Current lithographic resists depend on large polymeric materials, which are starting to limit further improvements in line-width roughness and feature size. Fullerene molecular resists use much smaller molecules to avoid this problem. However, such resists have poor radiation sensitivity. Chemical amplification of a fullerene derivative using an epoxy crosslinker and a photoacid generator is demonstrated. The sensitivity of the material is increased by two orders of magnitude, and 20-nm line widths are patterned.

Molecular resists, such as triphenylene derivatives, are small carbon rich molecules, and thus give the potential for higher lithographic resolution and etch durability, and lower line width roughness than traditional polymeric compounds. Their main limitation to date has been poor sensitivity. A new triphenylene derivative molecular resist, with pendant epoxy groups to aid chemically amplified crosslinking, was synthesized and characterized. The sensitivity of the negative tone, pure triphenylene derivative when exposed to an electron beam with energy 20 keV was ∼ 6 × 10–4 C cm–2, which increased substantially to ∼ 1.5 × 10–5 C cm–2 after chemical amplification (CA) using a cationic photoinitiator. This was further improved, by the addition of a second triphenylene derivative, to ∼ 7 × 10–6 C cm–2. The chemically amplified resist demonstrated a high etch durability comparable with the novolac resist SAL 601. Patterns with a minimum feature size of ∼ 40 nm were realized in the resist with a 30 keV electron beam.

Enhanced oil recovery (EOR) refers to the recovery of oil that is left behind in a reservoir after primary and secondary recovery methods, either due to exhaustion or no longer economical, through application of thermal, chemical or miscible gas processes. Most conventional methods are not applicable in recovering oil from reservoirs with high temperature and high pressure (HTHP) due to the degradation of the chemicals in the environment. As an alternative, electromagnetic (EM) energy has been used as a thermal method to reduce the viscosity of the oil in a reservoir which increased the production of the oil. Application of nanotechnology in EOR has also been investigated. In this study, a non-invasive method of injecting dielectric nanofluids into the oil reservoir simultaneously with electromagnetic irradiation, with the intention to create disturbance at oil-water interfaces and increase oil production was investigated. During the core displacement tests, it has been demonstrated that in the absence of EM irradiation, both ZnO and Al2O3 nanofluids recovered higher residual oil volumes in comparison with commercial surfactant sodium dodecyl sulfate (SDS). When subjected to EM irradiation, an even higher residual oil was recovered in comparison to the case when no irradiation is present. It was also demonstrated that a change in the viscosity of dielectric nanofluids when irradiated with EM wave will improve sweep efficiency and hence, gives a higher oil recovery.

Application of nanotechnology in enhanced oil recovery (EOR) has been increasing in recent years. After secondary flooding, more than 60% of the original oil in place (OOIP) remains in the reservoir due to trapping of oil in the reservoir rock pores. One of the promising EOR methods is surfactant flooding, where substantial reduction in interfacial tension between oil and water could sufficiently displace oil from the reservoir. In this research, instability at the interfaces is created by dispersing 0.05 wt% ZnO nanoparticles in aqueous sodium dodecyl sulfate (SDS) solution during the core flooding experiment. The difference in the amount of particles adsorbed at the interface creates variation in the localized interfacial tension, thus induces fluid motion to reduce the stress. Four samples of different average crystallite size were used to study the effect of particle size on the spontaneous emulsification process which would in turn determine the recovery efficiency. From the study, ZnO nanofluid which consists of larger particles size gives 145% increase in the oil recovery as compared with the smaller ZnO nanoparticles. In contrast, 63% more oil was recovered by injecting Al2O3 nanofluid of smaller particles size as compared to the larger one. Formation of a cloudy solution was observed during the test which indicates the occurrence of an emulsification process. It can be concluded that ultralow Interfacial tension (IFT) value is not necessary to create spontaneous emulsification in dielectric nanofluid flooding.

Zinc oxide (ZnO) with different nanoparticle (NP) sizes was prepared and synthesized by using the sol-gel method with organic precursor, followed by the characterization of the ZnO nanoparticle by using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) to identify the effect of nanoparticle sizes of ZnO on the viscosity of the nanofluid. The impact of nanoparticle sizes on EOR was investigated. Results showed both viscosity and interfacial tension (IFT) increased with the nanoparticle size.