In situ emulsification

Vittoratos, E. In-Situ Emulsification Interpreting Production Data in Supplementary Notes for Petroleum Emulsions and Applied Emulsion Technology, Schramm, L.L. (Ed.), Petroleum Recovery Institute Calgary, AB,... 

In Situ Emulsification. Coreflood experiments designed to cause permeability reductions by in situ creation of oil-in-water emulsions have been less successful than injection of externally produced emulsions, but still show significant reductions in permeability. The data are summarized in Table IX. 

The emulsification properties of the crude oil must be determined. Some crude oils can be emulsified with surfactant mixtures, others with caustic. Some crudes, such as Hasley Canyon (Table III), are difficult to emulsify. Experiments can be performed to determine if in situ emulsification is feasible, or if an emulsion must be injected. If in situ emulsification is feasible, loss of chemicals to reservoir rock is a problem to be addressed. If in situ emulsification is employed in conjunction with steam, it must be determined if chemicals are most effective when injected with the flowing steam or when chemical/steam injections are alternated. Relative permeabilities of the injected fluids should be determined. All of this information is needed to calculate the economics of scale-up to a specific field situation. 

So far we have looked at the flow of emulsions in porous media in this section we discuss some aspects of in situ emulsification in porous media that have received little attention. Some evidence suggests strongly that emulsions can be produced in the reservoir rock itself. A discussion on the formation of oil-field emulsions was given by Berkman and Egloff (50). They concluded that emulsions could be formed within the porous rock near the well bore where the velocity gradients (i.e., shear rates) were very high. Emulsions could also be formed as a result of mechanical agitation, for... 

Greater improvements in Enhanced Oil Recovery by alkaline flooding occurred in linear core floods where more in-situ emulsification was observed ... 

Previous work in our laboratory (1) implied that higher recovery efficiency may be achieved through the injection of an extracted resinous component, deasphaltened crude oil slug, prior to the injection of the alkaline phase. Results indicated that improvements in tertiary recovery efficiency did occur. The injection of this extracted resinous crude component aided in recovery by preventing asphaltene deposition, thereby increasing permeability of oil to rock, by forming an oil bank, and again, in-situ emulsification was observed to aid in enhanced recovery. 

More in-situ emulsification was observed with the sodium... 

The deasphaltened crude oil slug, extracted resinous component, may have improved tertiary recovery by preventing asphaltene deposition, thereby increasing permeability of oil to rock, by forming an oil bank, or again, in-situ emulsification may have enhanced oil recovery. 

As suspension polymerization is based on an in situ emulsification by turbulence, problems may arise during scale-up. The emulsification process is the real problem during the scale-up of laboratory-scale suspension polymerizations to an industrial level where today a typical reactor size is 200 m. ... 

The improved production efficiency of the NaOH/NaCl flood resulted from the formation of W/0, water-in-oil, emulsions under the limited shear conditions. The alkaline phase imbibes into the oleic phase as a result of the interfacial chemical reaction. The swollen oil phase, together with its altered configuration, reduces the area available for the passage of the alkaline floodwater. The produced water-oil ratio, WOR, decreases as a result of the lowered water mobility. The consistent presence of a light, emulsion phase at the very end of the oil production stage indirectly confirms the occurrence of the in situ emulsification step. The production efficiency increases with decrease in injection rate because of mass transfer limitations of the interfacial chemical reaction hydrodynamic effects would act in the opposite direction. The degree of in situ emulsification and wettability alteration, and the correspondent mobility reduction, depends on the residence time of the reactants in the core. 

This phenomenon of self-emulsification was first observed by Johannes Gad in 1878 when he gently layered a solution of lauric acid on top of an aqueous alkaline solution, thereby making a soap in situ but also forming an emulsion without the aid of external agitation. A laboratory curiosity for the next 50 or so years, the principle became recognized as being valuable for the formulation of herbicides and insecticides such as DDT. The concentrate could be reconstituted with ditch water and sprayed without the need to carry water to the site. 

The steps involved in the dean-up of an oil spill may involve any or all of containment, mechanical removal, shoreline cleanup, in situ burning, and dispersal. Dispersal is usually aimed at creating an O/W emulsion so that the dispersed oil drops can settle out as described above. Emulsification of the oil also accelerates microbial deg-... 

In situ formation of oil-in-water emulsions adds the requirement that the emulsification proceed spontaneously or at least with very little energy input due to mixing. Most such systems are associated with the agent-in-oil procedure, and spontaneous emulsification to oil-in-water emulsions sometimes occurs when aqueous caustic is mixed with petroleum oils containing naphthenic acids. Some researchers propose that mass transfer of the naturally occurring surfactants across the interface is the mechanism that causes this phenomena... 

Surface-active agents. Surface-active agents such as emulsifiers and surfactants play a very significant role in the stability of emulsions. They greatly extend the time of coalescence, and thus they stabilize the emulsions. Mechanisms by which the surface-active agents stabilize the emulsion are discussed in detail by Becher (19) and Coskuner 14). They form mechanically strong films at the oil-water interface that act as barriers to coalescence. The emulsion droplets are sterically stabilized by the asphaltene and resin fractions of the crude oil, and these can reduce interfacial tension in some systems even at very low concentrations (i7, 20). In situ emulsifiers are formed from the asphaltic and resinous materials found in crude oils combined with ions in the brine and insoluble dispersed fines that exist in the oil-brine system. Certain oil-soluble organic acids such as naphthenic, fatty, and aromatic acids contribute to emulsification 21). 

Surelease. a product of Colorcon. is produced by first melt extruding ethylcellulose with oleic acid and dibutyl sebacate (DBS) (or fractionated coconut oil) to form a molten plasticized polymeric blend. This molten blend of plasticized ethylcellulose is then introduced into an ammoniated water solution under high shear and pressure to disperse small droplets of plasticized ethylcellulose into the water phase (67). Ammonium oleate is produced in situ during this emulsification process to stabilize the colloidal ethylcellulose particles (67). Additional purified water is then added to reduce the final solids content of the pseudolatex dispersion to 25%. The Surelease coating system does not contain an ionic surfactant, and therefore does not exhibit the pH-dependent drug relea.se observed with Aquacoat ECD (66),... 

This section discusses the alkaline reaction with crude oil, which includes in situ soap generation, emulsification, and effect of ionic strength and pH on IFT. 

In emulsification and entrainment, the crude oil is emulsified in situ owing to IFT reduction, and it is entrained by the flowing aqueous alkaline solution (Subkow, 1942). The conditions for this mechanism to occur are high pH, low acid number, low salinity, and OAV emulsion size < pore throat diameter. 

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. 

The morphology of PP/PS blends was studied following the emulsification behavior as explained in Section 20.3.1.2. Figure 20.10 shows that the emulsification curve follows a typical trace, which was frequently reported for compatibilization of immiscible blends (28-30). It is clear that after a significant drop in particle size, an equilibrium value is reached at about 0.7% AICI3. This value has been taken as the cmc condition. It has to be remarked that the particle size decreases to one third of its initial value, reaching an equilibrium diameter of about 0.5 pm. Also, the particle size homogeneity increases with the catalyst content. It is shown by the decrease in error bars in Fig. 20.10. From these results, it is foreseen that the copolymer formed by the F-C reaction behaves as an efficient in situ compatibi-lizer for the PP/PS blend. 

Alkaline flooding is based on the reaction that occurs between the alkaline water and the organic acids, naturally occurring in some crudes, to produce in-situ surfactants or emulsifying soaps at the oil/water interface. Recent literature (i-J.) summarizes several proposed mechanisms by which alkaline water-flooding will enhance oil recovery. These mechanisms include emulsification and entrapment, emulsification and entrainment, and wettability reversal (oil-wet to water-wet or water-wet to oil-wet). Depending on the initial reservoir and experimental conditions with respect to oil, rock and injection water properties, one or more of these proposed mechanisms may be controlling. 

The approach was quite simple. Trial and error tests were conducted in pilot plants, eventually leading to flie selection of a convenient surfactant or surfactant package that produced an emulsion sufficiently stable to withstand shearing and storage from the field to the refinery. The emulsions were prepared in situ, by means of down-hole emulsification. A nonionic surfactant was the obvious choice since the formation water could be quite salty (53, 54, 59). 

Esterification reaction. A homogeneous mixture of polysaccharide (cellulose or amylose), water or ethanol, soap (added or created in situ) and fatty (octanoic) acid was obtained by emulsification at 2000 rpm using a high speed stirrer (homogenizer). Water or ethanol were then distilled off at 130°C for 30 min followed by the esterification reaction at 195 C for 2-6 hr. 

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