Viscosity of water-in-oil

Figure 8. Viscosity of water-in-oil emulsions Formulation B, 2.91 poise...

Viscosity of w/o Emulsions. The viscosity of water-in-oil emulsions at infinte shear depends on several factors ... 

Sherman, P. 1955c. Studies in oil-in-water emulsions. IV. The influence of the emulsifying agent on the viscosity of water-in-oil emulsions of high water content. J. Colloid Sci. 10,... 

Matsumoto, S., and Kohda, M., 1980, The viscosity of water-in-oil-in-water emulsions An attempt to estimate the water permeation coefficient of the oil layer from the viscosity changes in diluted systems on ageing under osmotic pressure gradients, J. Colloid Interface 73 13-20. 

Sherman [36] reported that the viscosity of water-in-oil emulsions stabilized with nonionic surfactants falls with time. Refer to Fig. 38. This phenomenon is controlled by the increase in the particle size caused by coalescence. The flocculation and coalescence rates will cause either the increase or decrease of the viscosity on aging [37]. 

Finally, permeability reductions attributed in the literature to the formation of water-in-oil emulsions are evidently caused by the high viscosity of those emulsions or to the formation of an oil film (lamella) across the pore throat (9). 

The behavior of water in oil microemulsions has been studied using different techniques light scattering, electrical conductivity, viscosity, transient electrical birefringence, ultrasonic absorption. All these experiments lead us to propose a picture of the microemulsions structure which assignes an important role to the fluidity of the interfacial region. 

Figure 11. Influence of additives on changes in the apparent viscosity of water/olive-oil/water emulsions within a short span of aging. "Reproduced with permission from Ref. 19. Copyright 1981, Food and Nutrition Press, Inc.. "...

The presence of emulsifiers (materials that promote emulsion formation) influences the ability to form an emulsion between petroleum and water. Emulsifiers act by lowering the interfacial tension between the phases and creating a strong adsorbed layer around the surface of the internal phase. Emulsifiers that are soluble in water (hydrophilic) promote the creation of oil in water emulsion. Alkaline soaps, starch and so on are such hydrophilic emulsifiers. Hydrophobic emulsifiers (i.e. soluble in petroleum) promote the formation of water in oil emulsions. Hydrophobic emulsifiers include resins dispersed in particle form within soot, clay and other substances. Petroleum emulsions can be characterized using properties such as viscosity, dispersion, density, electrical properties and stability. The viscosity of petroleum emulsion changes within wide ranges and depends on the viscosity of petroleum, temperature, and amounts of petroleum and water. 

Emulsification Emulsification is considered the second most important weathering process after a marine spill by which water is dispersed into oil in the form of small droplets. The mechanism of water-in-oil emulsion formation is not yet fully understood, but it probably starts with sea energy forcing the entry of small water droplets, about 10 to 25 /rm in size, into the oil. Emulsions of many types contain about 70% water. In general, water-in-oil emulsion can be categorized into four types (1) unstable oil simply does not hold water (2) entrained water droplets are simply held in the oil by viscosity to form an unstable emulsion, and it breaks down into water and oil within minutes or a few hours at most (3) semistable or meso-stable the small droplets of water are stabilized to a certain extent by a combination of the viscosity of the oil and interfacial action of asphaltenes and resins. For this to happen, the asphaltenes or resin content of the oU must be at least 3% by weight. The viscosity of meso-stable emulsions is 20 to 80 times... 

First, let us consider thin-film systems such as emulsions at interfaces. An emulsion is a quasi-stable suspension of fine drops of one liquid dispersed in another liquid. Emulsions, together with microemulsions, can be found in technology, and in almost every part of the petroleum production and recovery process in reservoirs, produced at wellheads, in many parts of the refining process, and in transportation pipelines [1-4]. Understanding the chemistry involved in the stabilization of emulsions and in crude oil emulsions in particular is important both for economic and environmental reasons. The presence of water in oil (w/o) and oil in water (o/w) results in several costly byproducts, such as corrosion, scale, and dissolved metals. Water-in-crude oil emulsions are responsible for the enormous increase in the viscosity of the crude oils produced in reservoirs. Transportation of the viscous crude oil through pipelines is difficult and adds to the cost of production of the oil. With increasing... 

These data indicate that there are windows of composition and viscosity which result in the forma tion of each of the types of water-in-oil states. The important oil composition factors are the asphaltene and resin contents. While asphaltenes are responsible for the formation of stable emulsions, a high asphal tene content can also result in a high viscosity, one that is above the region where stable emulsions form. The asphaltene/resin ratio is generally... 

The results of this study indicate that the formation of both stable and mesostable emulsions is due to the eombi-nation of surfaee-active forces from resins and asphaltenes and from viseous forces. Each type of water-in-oil state exists in a range of compositions and viscosities, the difference in composition between stable and mesostable emulsions is small. Stable emul sions have more asphaltenes and less resins and have a narrow viscosity window. Instability results when the oil has a high viscosity (over about 50 Pa.s) or a very low viscosity (under about 6 mPa.s) and when the resins and asphaltenes are less than about 3%. Water entrainment occurs rather than emulsion... 

Recovery of acidic oils with alkaline agents by an emulsification and coalescence mechanism Calcium hydroxide [Ca(0H)2] was used to verify the emulsification and coalescence concept since, as suggested by the theoretical and experimental evidence of an earlier section, the carboxylic salts of divalent ions form unstable emulsions of water-in-oil. The emulsification and coalescence concept was quantitatively verified by secondary and tertiary flooding of partially oil-saturated sandpacks. A tertiary chemical flood with Ca(0H)2 (pH = 12) recovered 44 percent of the waterflood residual oil from a 3.5-darcy Ottawa sandpack the oil had an acid number of 2 and a viscosity of 1.5 cp. A secondary caustic flood with Ca(0H)2 (pH = 12.32) recovered 82.3 percent of the original oil in place from a 0.25-darcy Ottawa sandpack the oil phase in this secondary flood had the same physical and chemical properties as the oil phase used in the tertiary mode flood. It should be noted that the microscopic mobilization efficiencies of these... 

Forced oscillation rheometry studies are the most accurate way of determining the type of emulsion. The visco-elastic properties are the simplest way to discriminate between the four types of water-in-oil states. The presence of significant elasticity clearly defines whether a stable emulsion has been formed. The viscosity by itself can be an indicator of the stability of an emulsion, although it is not necessarily conclusive, unless the viscosity of the starting oil is known. Colour is an indicator, but may not be definitive. Most stable emulsions are brown or reddish [157]. Some mesostable emulsions are brown in eolour and unstable emulsions are always the colour of the starting oil. Water content is not an indicator of stability and is error-prone beeause exeess water may be present. It should be noted that the water content of stable emulsions is greater than 70% and that unstable emulsions or entrained water-in-oil generally eontain less than 50% water. Water eontent of an emulsion after a period of about one week is more reliable than the water eontent of the emulsion when it has first formed becanse the oil and water will separate in a less stable emulsion. 

The differences between the four types of water-in-oil states are summarized in Table 15 [J56], It ean be seen in the table that precise analysis by viscosity wiU provide information on the stability of the emulsion and that this can also be nsed as a test of emulsion breakers. 

The combination of water-in-oil microemulsion and SCFs is a promising topic and may find more applications with some interesting advantages by utilizing the unique properties of SCFs. These include pressure-dependent variables such as viscosity, density, and diffusion rate, as well as the ability to readily manipulate the P-T phase behavior in the multicomponent micelle systems [13]. Much of the current research efforts in this area have been directed toward the SCF-continuous microemulsions. 

As described earlier in the section on bead or suspension polymers (Section 3.3.1.2), a solution of monomer(s) is prepared in water and then mixed into a low to medium viscosity non-volatile oil phase. In this process, which is often referred to as an inverse emulsion polymerisation technique, surfactants which promote the formation of water-in-oil emulsions are commonly used. These would usually be materials with an HLB (hydrophihc-lipophilic balance) value in the range 4—7, an example of which is sorbitan mono-oleate. In order to achieve the desired droplet particle size of a maximum around 1 pim prior to polymerisation, high shear homogenisers are used to assist the formation of such very small... 

S. Ajith, A.C. Jhon, and A.K. Rakshit 1994 Physicochemical studies of microemulsions pure, Appl. Chem. 66, 509-514 Z. Saidi, C. Matthew, 1. Peyrelasse, and C. Boned 1990 Percolation and structural exponents for the viscosity of microemulsions, Phys. Rev. A 42, 872-876 S. Ray, S.R. Bisal, and S.P. Moulik 1992 Studies on structure and dynamics of microemulsion 11 Viscosity behavior of water-in-oil microemulsion, J. Surf. Sci. Technol. 8, 191-208. 

Ray, S., Bisal, S., and Moulik, S. 1992 Studies on structure and dynamics of microemulsions II Viscosity behavior of water-in-oil microemulsions, J. Surface Sci. Technol. 8 191-208. 

Figure 12.1 Viscosity behavior of water-in-oil emulsions containing PEG7-hydrogenated castor oil/dicaprylyl ether/decyl oleate/glycerol/MgS04 = 3.5 7 7 5 0.7 as a function of water content (Reproduced by permission of Allured from ref 7)...

Templeton obtained data of the following type for the rate of displacement of water in a 30-/im capillary by oil (n-cetane) (the capillary having previously been wet by water). The capillary was 10 cm long, and the driving pressure was 45 cm of water. When the meniscus was 2 cm from the oil end of the capillary, the velocity of motion of the meniscus was 3.6 x 10 cm/sec, and when the meniscus was 8 cm from the oil end, its velocity was 1 x 10 cm/sec. Water wet the capillary, and the water-oil interfacial tension was 30 dyn/cm. Calculate the apparent viscosities of the oil and the water. Assuming that both come out to be 0.9 of the actual bulk viscosities, calculate the thickness of the stagnant annular film of liquid in the capillary. 

The exponential dependencies in Eq. (14-195) represent averages of values reported by a number of studies with particular weight given to Lefebvre [Atomization and Sprays, Hemisphere, New York, (1989)]. Since viscosity can vary over a much broader range than surface tension, it has much more leverage on drop size. For example, it is common to find an oil with 1000 times the viscosity of water, while most liquids fall within a factor of 3 of its surface tension. Liquid density is generally even closer to that of water, and since the data are not clear mat a liquid density correction is needed, none is shown in Eq. 

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