Emulsions in crude oil

Commercial Examples. The small but often undesirable contents of water dissolved in hydrocarbons may be removed by distillation. In drying benzene, for instance, the water is removed overhead in the azeotrope, and the residual benzene becomes dry enough for processing such as chlorination for which the presence of water is harmful. The benzene phase from the condenser is refluxed to the tower. Water can be removed from heavy liquids by addition of some light hydrocarbon which then is cooked out of the liquid as an azeotrope containing the water content of the original heavy liquid. Such a scheme also is applicable to the breaking of aqueous emulsions in crude oils from tar sands. After the water is removed... 

Tabic 5 Chemicals Used -as Demulsifiers for W/O Emulsions in Crude Oils from Literature Surs-ey to Date... 

The presence of these acids in crude oils and petroleum cuts causes problems for the refiner because they form stable emulsions with caustic solutions during desalting or in lubricating oil production very corrosive at high temperatures (350-400°C), they attack ordinary carbon steel, which necessitates the use of alloy piping materials. 

Other compounds which may be found in crude oil are metals such as vanadium, nickel, copper, zinc and iron, but these are usually of little consequence. Vanadium, if present, is often distilled from the feed stock of catalytic cracking processes, since it may spoil catalysis. The treatment of emulsion sludges by bio-treatment may lead to the concentration of metals and radioactive material, causing subsequent disposal problems. 

An important industrial example of W/O emulsions arises in water-in-crude-oil emulsions that form during production. These emulsions must be broken to aid transportation and refining [43]. These suspensions have been extensively studied by Sjoblom and co-workers [10, 13, 14] and Wasan and co-workers [44]. Stabilization arises from combinations of surface-active components, asphaltenes, polymers, and particles the composition depends on the source of the crude oil. Certain copolymers can mimic the emulsion stabilizing fractions of crude oil and have been studied in terms of their pressure-area behavior [45]. 

Crude oils contain various amounts of indigenous surface-active agents that stabilize water-in-oil emulsions. Therefore crude oils may stabilize such emulsions. It has been shown that the effectiveness of a dispersant is dependent on both the dispersant type and the specific crude oil [309]. However, there is no apparent correlation between the degree of emulsion-forming tendency of the crude oil, which is a function of the indigenous surfactant content, and the effectiveness of the dispersant. In general, indigenous surfactants in crude oil reduce the effectiveness of the dispersant, but to an unpredictable level. 

In the production of crude oil, the greatest part of the crude oil occurs as a water-in-oil emulsion. The composition of the continuous phase depends on the water/oil ratio, the natural emulsifier systems contained in the oil, and the origin of the emulsion. The natural emulsifiers contained in crude oils have a complex chemical structure, so that, to overcome their effect, petroleum-emulsion demulsifiers must be selectively developed. As new oil fields are developed, and as the production conditions change at older fields, there is a constant need for demulsifiers that lead to a rapid separation into water and oil, as well as minimal-residual water and salt mixtures. 

DEMULSIFICATION TESTS. Demulsification tests were conducted using standard bottle test procedures to evaluate the relative performance of Thin Film Spreading Agents in coalescing emulsions of formation brine in crude oil under reservoir conditions. 

Emulsifiers. To form an emulsion the system must have present the water and oil, agitation, and also of primary Importance, the emulsifying agents. Such agents are always found in crude oil and include asphaltines (a general term applied to a large... 

Two groups of elements appear in significant concentrations in the original crude oil, associated with well-defined types of compounds. Zinc, titanium, calcium, and magnesium appear in the form of organometallic soaps with surface-active properties, adsorbed in the water-oil interfaces, and act as emulsion stabilizers. However, vanadium, copper, nickel, and part of the iron found in crude oils seem to be in a different class and are present as oil-soluble compounds (Reynolds, 1997). These metals are capable of complexing with pyrrole pigment... 

Salts such as sodium, calcium, and magnesium chloride are generally contained in water suspended in the oil phase of hydrocarbon feedstocks.9 Other impurities are also present in crude oils as mechanical suspensions of silt (dirt), iron oxides, sand, and crystalline salt.14 These contaminants must be removed before processing the crude oil feeds thus, the best method is mixing the crude oil with water and creating an emulsion.12... 

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). 

In extreme cases, material can adsorb at an interface to create a film. Interfacial film formation can occur in crude-oil systems and has been reported by Blair (16), and by Reisberg and Doscher (17), Film formation is relatively common with crude oils and can effectively stabilize emulsions by preventing droplet coalescence even with high values of interfacial tension. 

IONS OR DISPERSIONS OF HEAVY CRUDE OIL in water or brine have been used in several parts of the world for pipeline transportation of both waxy and heavy asphaltic-type crude oils. The hydrodynamically stabilized dispersion transportation concept is described by the Shell Oil Corporation core flow technology (i). The use of surfactants and water to form oil-in-water emulsions with crude oils is the subject of a long series of patents and was proposed for use in transporting Prudhoe Bay crude oil (2). Furthermore, surfactants may be injected into a well bore to effect emulsification in the pump or tubing for the production of heavy crude oils as oil-in-water emulsions (3, 4). 

Recently, we have shown that sulfonated PHP can act as a demulsifier for highly stable emulsions like crud and water-in-crude oil emulsions. The mechanism of demulsification is that sulfonated PHP removes selectively surface active species in the emulsion, causing destabilization. At the same time, it also adsorbs metal ions, thus achieving two functions at the same time. As a result, these materials are called demulsifier adsorbers. In highly stable emulsions where neither electric field nor demulsifier adsorbers are effective, the combination of these two methods appears to create synergy for separation. 

Fig. 9 Process intensification in water-in-crude oil separation under electric field with or without PHP variation of percentage of separation with electric field strength applied over a distance of 10 cm when the emulsion flow rate is kept constant at 60ml/min. Percentage separation into oil-water layers is carried out either immediately (within 10 min) or after 1 hr of emulsion passing through the electric field. (From Ref. " l) (View this art in color at www.dekker. com.)...

Akay, G. Dogru, M. Calkan, B. Calkan, O.F. Flow induced phase inversion phenomenon in process intensification and micro-reactor technology. Process intensification in water-in-crude oil emulsion separation by simultaneous application of electric field and polymeric demulsifiers. In Microreact Technology and Process Intensification Wang, Y., Halladay, J., Eds. Oxford University Press Oxford, 2005 Chapter, 18. 

Akay, G. Noor, Z.Z. Dogru, M. Process intensification in water-in-crude oil emulsion separation... 

Borve KGN, Sjoblom J, Stenius P. Water in crude oil emulsions from the Norwegian continental shelf. 5. A comparative monolayer study of model polymers. Colloids Surf 1992 63 241-251. 

Kim YH, Nikolov AD, Wasan DT, Diaz-Araumzo H, Shetty CS. Demulsifi-cation of water in crude oil emulsions effects of film tension, elasticity, dif-... 

Bhardwaj A, Hartland S. Kinetics of coalescence of water droplets in water in crude oil emulsions. J Dispersion Sci and Technol 1994 15 133-146. 

Miller DJ, Bohm R. Optical studies of coalescence in crude oil emulsions. J Petroleum Sci Eng 1993 9 1-8. 

Taylor SE. Investigations into the electrical and coalescence behavior of water in crude oil emulsions in high voltage gradients. Colloids Surf 1988 29 29-51. 

Aveyard R, Binks BP, Fletcher PDI, Lu JR. The resolution of water in crude oil emulsions by the addition of low molar mass demulsifiers. J Colloid Interface Sci 1990 139 128-138. 

Emulsions of crude oil in aqueous alkaline solutions were prepared by a hand homogenizer. Immediately after homogenization a representative sample of the emulsion was placed in a hemo-cytometer and photographed through the microscope. The hemocyto-meter had a specified grid volume of 10 mls. It was designed for a magnification of approximately 400 (i.e. 40X objective). 

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