Measurement of low interfacial tensions by capillary wave spectroscopy. Study of an oil-water-surfactant system near its phase inversion

2007 ◽  
pp. 100-108 ◽  
Author(s):  
D. Wielebinski ◽  
G. H. Findenegg
Keyword(s):  
Phase Inversion ◽  
Capillary Wave ◽  
Spectroscopy Study ◽  
Interfacial Tensions ◽  
Surfactant System ◽  
Oil Water

Evaluation of the Interfacial Tension Between a Microemulsion and the Excess Dispersed Phase

1981 ◽  
Vol 21 (05) ◽  
pp. 593-602 ◽  
Author(s):  
E. Ruckenstein
Keyword(s):  
Interfacial Tension ◽  
Oil Recovery ◽  
Phase Inversion ◽  
The Other ◽  
Dispersed Phase ◽  
Middle Phase ◽  
Inversion Point ◽  
Interfacial Tensions ◽  
Dispersed Medium ◽  
Oil Water

Abstract From a consideration of the thermodynamic stability of microemulsions, one can establish a relation between the interfacial tension y at the surface of the globules and the derivative, with respect to their radius re, of the entropy of dispersion of the globules in the continuous medium. Expressions for the entropy of dispersion are used to show that gamma is approximately proportional to kT/r2e, where k is Boltzmann's constant and T is the absolute temperature. Since the environment of the interface between the microemulsion and the excess dispersed medium is expected to be similar to that at the surface of the globules, these expressions are used to evaluate the interfacial tension between microemulsion and excess dispersed medium. Values between 10 and 10 dyne/cm that decrease with increasing radii are obtained, in agreement with the range found experimentally by various authors. The origin of the very small interfacial tensions rests ultimately in the adsorption of surfactant and cosurfactant on the interface between phases. The effect on the interfacial tension of fluctuations from one type of microemulsion to the other, which may occur near the phase inversion point, is discussed. Introduction The system composed of oil, water, surfactant, cosurfactant, and salt exhibits interesting phase equilibria. For sufficiently large concentrations of surfactant, a single phase can be formed either as a microemulsion or as a liquid crystal. In contrast, at moderate surfactant concentrations, two or three phases can coexist. For moderate amounts of salt (NaCl), an oil phase is in equilibrium with a water-continuous microemulsion, whereas for high salinity, an oil-continuous microemulsion coexists with a water phase. At intermediate salinity, a middle phase (probably a microemulsion) composed of oil, water, surfactants, and salt forms between excess water and oil phases. Extremely low interfacial tensions are found between the different phases, with the lowest occurring in the three-phase region. These systems have attracted attention because of their possible application to tertiary oil recovery. It has been shown that the displacement of oil is most effective at very low interfacial tensions.Microemulsions have been investigated with various experimental techniques, such as low-angle X-ray diffraction, light scattering, ultracentrifugation, electron microscopy, and viscosity measurements. These have shown that the dispersed phase consists of spherical droplets almost uniform in size. While it is reasonable to assume that the microemulsions coexisting with excess oil or water contain spherical globules of the dispersed medium, the structure of the middle-phase microemulsion is more complex. Experimental evidence obtained by means of ultracentrifugation indicates, however, that at the lower end of salinity the middle phase contains globules of oil in water, while at the higher end the middle phase is oil continuous. A phase inversion must occur, at an intermediate salinity, from a water-continuous to an oil-continuous microemulsion. The free energies of the two kinds of microemulsions are equal at the inversion point. Since their free energy of formation from the individual components is very small, small fluctuations, either of thermal origin or due to external perturbations, may produce changes from one type to the other in the vicinity of the inversion point. As a consequence, near this point, it is possible that the middle phase is composed of a constantly changing mosaic of regions of both kinds of microemulsions. SPEJ P. 593^

Effect of Shear and Water Cut on Phase Inversion and Droplet Size Distribution in Oil–Water Flow

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Mo Zhang ◽  
Ramin Dabirian ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Phase Inversion ◽  
Droplet Size Distribution ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Water Emulsion ◽  
Inversion Region ◽  
Oil Water ◽  
Water Cut

Oil–water dispersed flow occurs commonly in the petroleum industry during the production and transportation of crudes. Phase inversion occurs when the dispersed phase grows into the continuous phase and the continuous phase becomes the dispersed phase caused by changes in the composition, interfacial properties, and other factors. Production equipment, such as pumps and chokes, generates shear in oil–water mixture flow, which has a strong effect on phase inversion phenomena. The objective of this paper is to investigate the effects of shear intensity and water cut (WC) on the phase inversion region and also the droplet size distribution. A state-of-the-art closed-loop two phase (oil–water) flow facility including a multipass gear pump and a differential dielectric sensor (DDS) is used to identify the phase inversion region. Also, the facility utilizes an in-line droplet size analyzer (a high speed camera), to record real-time videos of oil–water emulsion to determine the droplet size distribution. The experimental data for phase inversion confirm that as shear intensity increases, the phase inversion occurs at relatively higher dispersed phase fractions. Also the data show that oil-in-water emulsion requires larger dispersed phase volumetric fraction for phase inversion as compared with that of water-in-oil emulsion under the same shear intensity conditions. Experiments for droplet size distribution confirm that larger droplets are obtained for the water continuous phase, and increasing the dispersed phase volume fraction leads to the creation of larger droplets.

Nature of the oil/water interface and equilibrium surfactant aggregates in systems exhibiting low tensions

1988 ◽  
Vol 66 (12) ◽  
pp. 3031-3037 ◽  
Author(s):  
Robert Aveyard ◽  
Bernard P. Binks ◽  
Thomas A. Lawless ◽  
Jeremy Mead
Keyword(s):  
Molecular Structure ◽  
Sodium Chloride ◽  
Water Interface ◽  
Rich Phase ◽  
Aqueous Sodium ◽  
Interfacial Tensions ◽  
Aerosol Ot ◽  
Surfactant Aggregates ◽  
Monolayer Adsorption ◽  
Oil Water

Oil/water interfacial tensions are reported for systems containing pure alkane, aqueous sodium chloride, and a pure anionic surfactant, either Aerosol OT or p-dihexylbenzene sodium sulphonate (DHBS). Evidence is produced to support the claim that monolayer adsorption at the oil/water interface can produce ultralow tensions (~ 1 µN m−1), and that the presence at the interface of a third, surfactant-rich phase is not necessary. The aggregation of DHBS and its distribution between oil and aqueous phases of various salinities have been investigated. It has been confirmed that the behaviour of DHBS in these respects is similar to that of Aerosol OT, as might be expected from its molecular structure. The sizes of microemulsion droplets in equilibrium with planar adsorbed monolayers have been determined, and related to the tensions of the plane oil/aqueous phase interfaces using simple existing theory.

Gas solubilities in a three-phase oil—water—surfactant system

1988 ◽  
Vol 123 (2) ◽  
pp. 437-441 ◽  
Author(s):  
A.R Nanda ◽  
N Nugara ◽  
H.L Flanagan ◽  
A.D King
Keyword(s):  
Surfactant System ◽  
Three Phase ◽  
Gas Solubilities ◽  
Oil Water

Effect of glycerol addition on phase inversion in horizontal dispersed oil–water pipe flows

2011 ◽  
Vol 35 (4) ◽  
pp. 628-635 ◽  
Author(s):  
Kwun Ho Ngan ◽  
Karolina Ioannou ◽  
Lee D. Rhyne ◽  
Panagiota Angeli
Keyword(s):  
Phase Inversion ◽  
Water Pipe ◽  
Pipe Flows ◽  
Dispersed Oil ◽  
Oil Water

Characterization of Oil-Water Dispersions/Emulsions Flowing Through Restrictions

2010 ◽  
Author(s):  
Mari´a V. Parra ◽  
Luis Go´mez ◽  
Ram S. Mohan ◽  
Ovadia Shoham ◽  
Gene Kouba ◽  
...  
Keyword(s):  
Phase Inversion ◽  
Processing Technique ◽  
Orifice Plate ◽  
Image Processing Technique ◽  
Inversion Point ◽  
Plate Size ◽  
Point Image ◽  
Oil Water ◽  
Water Cut

An experimental study of the characterization of oil-water dispersions/emulsions flowing through an orifice plate was carried out in the Dispersion Characterization Rig® (DCR), a state-of-the-art facility for studying the separation process of dispersions/emulsions. In this study, experiments with distilled water and mineral oil at different choke pressures, velocities, and different orifice sizes were conducted in order to find the phase-inversion zone and observe how the separation profile is affected by these variables. Bulk flow kinetic energy and water cut, are plotted against the pressure drop in the orifice plate to find the inversion point. Image processing technique is used to measure the coalescing and sedimenting profiles with respect to time. Results indicate a good agreement between the two methods used to find where phase inversion occurs and that this is affected by velocities, choke pressure and orifice plate size; also that emulsions become more stable when smaller size of orifice plates are used, as expected.

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