Viscous Emulsions

2 Drop Dispersion. Both turbulence and shear can break up drops in concentrated systems, but due to the dampening of eddies, it is likely that mean shear plays an important role in drop dispersion. This effect has been quantified 

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Emulsions. Emulsion fluids and foams came into routine use in competition with crosslinked fluids during 1970-80. Simple, barely stable emulsions had been used early in fracturing. These were mainly emulsified acids that "broke" when the acid spent on the formation surfaces. In the late 1960 s Kiel became a proponent of very high viscosity oil fluids as a method to place exceptional (at the time) amounts of proppant(337,338). To avoid the frictional resistance typical of gelled oils he advanced the concept of preparing a very viscous oil-external emulsion with one part fresh water, 0.1% sodium tallate surfactant, and two parts oil. The viscous emulsion had to be pumped simultaneously with a water stream to minimize frictional pressure. This process was clumsy and still... 

Other latexes which have been produced by this method include poly(butyl methacrylate), poly(butyl acrylate) and poly(styrene/DVB) [161]. Additionally, polymer blends were produced by mixing, under high shear, HIPEs of partially polymerised monomer, followed by completion of polymerisation. The conversion prior to blending had to be less than 5%, to allow efficient mixing of the highly viscous emulsions. The materials thus produced resembled agglomerates of latex particles, due to copolymerisation at the points of contact of partially polymerised droplets. 

At the point where the MIP is at a minimum, injection of ammonia gas results in a steep increase in the amount of high-molecular-weight materials with a concurrent rise in pH value. Both these processes are highly desirable. Ammonia is added until the desired pH value is obtained ( 3.5 to 4.0). At this point, the resin preparation is a viscous emulsion of dark brown color. The advantage of this method of resin preparation is its adaptability to continuous plug-flow reaction, unlike the Phase I resin, which is more suited to batch reaction. 

Bnulsion Capacity. The most viscous emulsions of peanut meal with mayonnaise consistencies were produced from suspensions at pH 1.5 in water and 0.1 M NaCl, and by the water suspension adjusted from pH 6.7 to 4.0 to 8.2 (Figure 6). At pH 4.0, poor emulsifying properties were noted for all suspensions. The two-step pH adjustment from 6.7 to 4.0 to 6.7 improved emulsification properties of only the water suspension over those of samples where the pH was not adjusted or was minor. 

CNC Antifoam 100 is a viscous emulsion and contains 10% silicone. It is easily dllutible with water and as little as 5% or 10% dilutions remain stable for many hours. These dilutions have immediate defoaming action. 

Consistency SI. viscous emulsion Color White pH (5%) Approx. 7 Viscosity Approx. 1000... 

The most common variation to the API, ASTM, and IP methods for field use is the addition of demulsifier or knockout drops to facilitate the separation of the phases. The demulsifier is generally added at concentrations significantly above what would be normal operational levels. The disadvantages of this technique are that it does not separate the water and solids, and it is not useful for very high-water-content streams. Filling the centrifuge tube with a representative sample can also be difficult, especially with viscous emulsions. 

To stabilize emulsions, a surfactant, which increases the repulsive force between oil droplets, is used. Nonionic surfactants are the preferred type because they are effective in brines, are generally cheaper, and often form less viscous emulsions than do ionic surfactants. In addition, their emulsions are easier to break, and they do not introduce inorganic residues that might lead to refinery problems. They are chemically stable at oil reservoir temperatures and are noncorrosive and nontoxic. The surfactant type and concentration required for a particular situation can be determined by conducting laboratory tests. A typical concentration of 0.1 lb of surfactant per barrel of oil is used for emulsions containing about 50-70% oil (2). 

Fiori and Farouq Ali (73) proposed the emulsion flooding of heavy-oil reservoirs as a secondary recovery technique. This process is of interest for Saskatchewan heavy-oil reservoirs, where primary recovery is typically 2-8%. Water-flooding in these fields produces only an additional 2-5% of the original oil in place because of the highly viscous nature of the oil. In laboratory experiments, a water-in-oil emulsion of the produced oil is created by using a sodium hydroxide solution. The viscous emulsion formed is injected into the reservoir. Its high viscosity provides a more favorable mobility ratio and results in improved sweep of the reservoir. Important parameters include emulsion stability and control of emulsion viscosity. 

The ability of microbes to grow in an environment is influenced by its oxidation-reduction balance (redox potential), as they will require compatible terminal electron acceptors to permit their respiratory pathways to function. The redox potential even in fairly viscous emulsions may be quite high due to the appreciable solubility of oxygen in most fats and oils. 

Other mechanisms, which are not discussed here, are more or less related to emulsification and reduced IFT due to in situ generation of soap. One application based on these mechanisms is to inject alkaline solution and gas, simultaneously or alternately, to improve sweep efficiency. As we know, there is a viscous fingering problem for gas injection only. Injection of an alkaline solution in a reservoir with active crude oil will generate 0/W and W/0 emulsions. The high viscous emulsions and foam formed through gas injection will reduce the viscous fingering problem. In this case, CO2 cannot be injected because it will neutralize the alkaline solution. 

Mayonnaise, on the other hand, is a relatively stable emulsion due mostly to high viscosity (more precisely, viscoelasticity), though surfactants are also present. The oil and water in mayonnaise cannot separate into phases because the emulsion droplets do not have enough energy for much movement. In less viscous emulsions, surfactants are responsible for stability. They reduce interfacial tension for the formation of small particles that either repel or very weakly attract each other. Brownian motion must be able to counter the effects of interparticle attraction, sedimentation, or creaming, which is floatation. Micellar suspensions could also be considered microemulsions, although this is debatable. 

The 80% oil emulsion is often very viscous, but the stirring efficiency is quite good and the drop size is reduced at a low energy expense. Such stirring of a very viscous emulsion often results in a bimodal emul sion of a lower viscosity than expected. 

To prevent the formation of a viscous emulsion, the mixture should be well agitated. 

For very viscous emulsions, the emulsion may be pre-heated and then test the samples at 60°C 5°C. Alternatively, the 50 g of diluted emulsion may be diluted further with either the Sa or the S.. solution, as appropriate. 

In conclusion, we have observed the individual and combined effects that the heavy, naturally occurring asphaltic components have upon the interfacial activity and structure of an acidic crude oil-aqueous alkaline system. The subsequent film formation that these components exhibit when contacted with a caustic phase suggests the presence of a stabilizing barrier that may impede coalescence of viscous emulsions formed in situ during flooding processes. 

Both oil-in-acid and acid-in-oil emulsions form during well aeid stimulation [JO]. The latter type of emulsions, however, ean cause serious problems because of its high viseosity. These viscous emulsions are slow to return into the wellbore and result in loss of produetion, espeeiaUy in low-pressure reservoirs. 

This aim is even better achieved if, after a temporary high shear stress, the recovery of the higher viscosity is delayed. This phenomenon is called thixotropy. This phenomenon can often be seen in daily practice. For example, highly viscous emulsions like tomato ketchup and other cooking sauces temporarily have a lower viscosity after vigorous shaking. Also cutaneous emulsions often exhibit thixotropic behaviour. 

Optimum surfactant composition is distinctly different for weathered and unaltered diesel oil. The application of single nonionic surfactants leads to a substantial reduction of soil permeability or even to clogging. This is due to formation of viscous emulsions. This can be avoided by using surfactant blends. This way, the complex requirements for in-situ application, i.e., maintenance of permeability, low surfactant losses and low residual levels of oil can be achieved. 

A common fault in determining non volatile contents of latices is to use too thick a sample. Not more than Ig of emulsion should be used in each tray, and in the case of viscous emulsions, the sample should be quickly spread with a small spatula before weighing. Drying should be for 30 minutes at 130°C. 

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