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.
Highlights
For several years, oil has been produced from the earth using a variety of production techniques, typically occurring in three phases: primary, secondary and tertiary oil recovery [1]
It was observed that the oil displacement mechanism is dependent on the particle size of ZnO NFs, where the interfacial tensions (IFT) and contact angle decreases with the decrease in particle size
ZnO@800 NPs (117.1 nm) show a greater change in oil recovery between conventional and EM-assisted nanoflooding. This can be the reason of larger disturbance in interface due to bigger particle size under orientational polarization, providing a noticeable reduction in IFT from 13.38 to 11.60 mN/m
Summary
Oil has been produced from the earth using a variety of production techniques, typically occurring in three phases: primary, secondary and tertiary oil recovery [1]. Water/gas is commonly injected to re-pressurize the target formation, which provide the energy as well as mobility to sweep the residual oil to the wellbore for recovery. The injected fluids act as a supplement to the existing natural energy in the reservoir to displace oil. The injected fluids in tertiary recovery processes, known as enhanced oil recovery (EOR) processes, interact with the reservoir rock/oil system. These interactions can be resulted in lower interfacial tensions (IFT), oil viscosity reduction, oil swelling, wettability modification, and/or favorable phase behavior
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