The
combination of chemical enhanced oil recovery (CEOR) and low salinity water (LSW) flooding is one of the
most attractive enhanced oil recovery (EOR) methods. While several
studies on CEOR have been performed to date, there still exists a
lack of mechanistic understanding on the synergism between surfactant,
alkali and LSW. This synergism, in terms of fluid–fluid interactions,
is experimentally investigated in this study, and mechanistic understanding
is gained through fluid analysis techniques. Two surfactants, one
cationic and one anionic, namely an alkyltrimethylammonium bromide
(C19TAB) and sodium dodecylbenzenesulfonate (SDBS), were
tested, together with NaOH used as the alkali, diluted formation brine
used as the LSW, and the crude oil was collected from an Iranian carbonate
oil reservoir. Fluids were analyzed using pendant drop method for
interfacial tension (IFT) measurement, and Fourier transform infrared
spectroscopy for determination of aqueous and oleic phase chemical
interaction. The optimum concentration of LSW for IFT reduction was
investigated to be 1000 ppm. Additionally, both surfactants reduced
IFT significantly, from 28.86 mN/m to well below 0.80 mN/m, but in
the presence of optimal alkali concentration the IFT dropped further
to below 0.30 mN/m. IFT reduction by alkali was linked to the production
of three different types of in situ anionic surfactants, while in
the case of anionic and cationic surfactants, saponification reactions
and the formation of the C19TAOH alcohol, respectively,
were linked to IFT reduction. The critical micelle concentration and
optimal alkali concentration when using cationic C19TAB
were significantly lower than with the anionic surfactant; respectively:
335 vs 5000 ppm, and 500 vs 5000 ppm. However, it was found that SDBS
was more compatible with NaOH than C19TAB, due to occurrence
of alkali deposition with the latter beyond the optimal point.
Nanofluid flooding, as a new technique to enhance oil recovery, has recently aroused much attention. The current study considers the performance of a novel iron-carbon nanohybrid to EOR. Carbon nanoparticles was synthesized via the hydrothermal method with citric acid and hybridize with iron (Fe3O4). The investigated nanohybrid is characterized by its rheological properties (viscosity), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis. The efficiency of the synthetized nanoparticle in displacing heavy oil is initially assessed using an oil–wet glass micromodel at ambient conditions. Nanofluid samples with various concentrations (0.05 wt % and 0.5 wt %) dispersed in a water base fluid with varied salinities were first prepared. The prepared nanofluids provide high stability with no additive such as polymer or surfactant. Before displacement experiments were run, to achieve a better understanding of fluid–fluid and grain–fluid interactions in porous media, a series of sub-pore scale tests—including interfacial tension (IFT), contact angle, and zeta potential—were conducted. Nanofluid flooding results show that the nanofluid with the medium base fluid salinity and highest nanoparticle concertation provides the highest oil recovery. However, it is observed that increasing the nanofluid concentration from 0.05% to 0.5% provided only three percent more oil. In contrast, the lowest oil recovery resulted from low salinity water flooding. It was also observed that the measured IFT value between nanofluids and crude oil is a function of nanofluid concentration and base fluid salinities, i.e., the IFT values decrease with the increase of nanofluid concentration and base fluid salinity reduction. However, the base fluid salinity enhancement leads to wettability alteration towards more water-wetness. The main mechanisms responsible for oil recovery enhancement during nanofluid flooding is mainly attributed to wettability alteration toward water-wetness and micro-dispersion formation. However, the interfacial tension (IFT) reduction using the iron-carbon nanohybrid is also observed but the reduction is not significant.
Many studies have investigated natural
convection heat transfer
from the outside surface of horizontal and vertical cylinders in both
constant heat flux and temperature conditions. However, there are
poor studies in natural convection from inclined cylinders. In this
study, free convection heat transfer was examined experimentally from
the outside surface of a cylinder for glycerol and water at various
heat fluxes. The tests were performed at 10 different inclination
angles of the cylinder, namely, φ = 0°, 10°, 20°,
30°, 40°, 50°, 60°, 70°, 80°, and 90°,
measured from the horizon. Our results indicated that the average
Nusselt number reduces with the growth in the inclination of the cylinder
to the horizon at the same heat flux, and the average Nusselt number
enhanced with the growth in heat flux at the same angle. Also, the
average Nusselt number of water is greater than that of glycerol.
A new experimental model for predicting the average Nusselt number
is suggested, which has a satisfactory accuracy for experimental data.
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