Acid-in-oil emulsion

Acid-in-oil emulsion can extend the propagation of acid considerable distances into a reservoir because the continuous (oil) phase prevents or minimizes contact between the acid and the rock [4,678,689]. Emulsification also increases viscosity and will improve the distribution of the acid in layered and heterogeneous reservoirs. Acidizing foams are aqueous, in which the continuous phase is usually hydrochloric acid (carbonate reservoirs) or hydrofluoric acid (sandstone reservoirs), or a blend, together with suitable surfactants and other stabilizers [345,659]. Foaming an acidizing fluid increases its effective viscosity, providing mobility control when it is injected [678]. 

To control the reaction rate of the acid, retarders such as alkyl sulfonates, alkyl phosphonates and alkyl amines are used to form hydrophobic films on carbonate surfaces. These protective films act as a barrier to slow acid attack. Another method involves the use of foaming agents to stabilize the carbon dioxide foam that is created when CO2 is released as a product of the acidetching reaction. This CO2 foam acts as a barrier to slow acid attack. Yet another method for controlling the acid activity in an oil well is the use of emulsions containing kerosene or diesel as the continuous oil phase and hydrochloric acid as the dispersed aqueous phase. Acid-in-oil emulsions are most commonly used because oil separates the acid from the carbonate surface (and from machine parts, thus reducing the level of corrosion). Moreover, acid reaction rates can be further decreased by surfactant retarders that increase the wettability of the carbonate surface for oil. 

The petroleum industry does not remain unaffected by corrosion (as was alluded to in the discussion on acid-in-oil emulsions above). Indeed, corrosion is a common phenomenon endured by almost every industry. The metallic parts used everywhere from oil wells to refineries and petrochemical plants are susceptible to corrosion. In 1999, in the USA alone, corrosion was held responsible for approximately 300 billion of lost revenue, of which more than one third could have been saved by using available methods of corrosion control (36). 

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. 

The American Petroleum Institute recommends conducting acid sludge test API RP 42 before performing acidizing jobs in the field [39], These tests are used to determine the type and concentration of the surfactant (nonionic or anionic) needed to break acid-in-oil emulsions in a reasonable period of time. It is very important to perform the tests using live and spent acids at reservoir temperature. Spent acid should be prepared in the lab using formation rock. The live and spent acids should include acid additives as per field formula. The crude oil sample should be fresh, and free from water and oilfield chemicals (e.g., scale inhibitors, demulsifiers, etc.). 

C. W., and B. D. Miller. 1974. New, low viscosity acid in oil emulsions. Paper SPE 5159, presented at the Society of Petroleum Engineers National Meeting and Exhibition, Houston. Ford, W. G. F. 1981. Foamed acid—an effective stimulation fluid. Journal of Petroleum Technology. July 7. 

Because of the zwitterion formation, mutual buffering action, and the presence of strongly acid components, soybean phosphoHpids have an overall pH of about 6.6 and react as slightly acidic in dispersions-in-water or in solutions-in-solvents. Further acidification brings soybean phosphoHpids to an overall isoelectric point of about pH 3.5. The alcohol-soluble fraction tends to favor oil-in-water emulsions and the alcohol-insoluble phosphoHpids tend to promote water-in-oil emulsions. 

The basic patent (US Patent 3256219) indicates that the system is viable with conventional resins although special grades have been developed that are said to be particularly suitable. One example in the patent recommends the use of a polyester prepared using a maleic acid, phthalic acid and propylene glycol ratio of 2 1 33 and with an acid value of 40. To 500g of such a resin are added 10g of benzoyl peroxide and 167 g of styrene. Water 600 g is then stirred in at 5-10°C until a white creamy water-in-oil emulsion is obtained. A solution of 0.8 g of dimethyl-p-toluidine in lOOg of styrene is stirred into the emulsion and the resin is cast between plates and cured at 50°C. 

Although low-molar-mass aliphatic polyesters and unsaturated polyesters can be synthesized without added catalyst (see Sections 2.4.1.1.1 and 2.4.2.1), the presence of a catalyst is generally required for the preparation of high-molar-mass polyesters. Strong acids are very efficient polyesterification catalysts but also catalyze a number of side reactions at elevated temperature (>160°C), leading to polymers of inferior quality. Acid catalysts are, therefore, not much used. An exception is the bulk synthesis of hyperbranched polyesters reported in Section 2.4.5.1, which is carried out at moderate temperature (140°C) under vacuum in the presence of p-toluene sulfonic acid catalyst. The use of strongly acidic oil-soluble catalysts has also been reported for the low-temperature synthesis of polyester oligomers in water-in-oil emulsions.216... 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

Traditionally, butter was made by allowing cream to separate from the milk by standing the milk in shallow pans. The cream is then churned to produce a water in oil emulsion. Typically butter contains 15% of water. Butter is normally made either sweet cream or lactic, also known as cultured, and with or without added salt. Lactic butter is made by adding a culture, usually a mixture of Streptococcus cremoris, S. diacetylactis and Betacoccus cremoris. The culture produces lactic acid as well as various flavouring compounds, e.g. diacetyl, which is commonly present at around 3 ppm. As well as any flavour effect the lactic acid inhibits any undesirable microbiological activity in the aqueous phase of the butter. Sweet cream butter has no such culture added but 1.5 to 3% of salt is normally added. This inhibits microbiological problems by reducing the water activity of the aqueous phase. It is perfectly possible to make salted lactic butter or unsalted sweet cream butter if required. In the UK most butter is sweet cream while in continental Europe most butter is lactic. 

The fact that sodium salts of fatty acids will form, an oil in water emulsion whilst the addition of calcium salts yields a water in oil emulsion is as we have noted explicable on the hypothesis that the cross-section of the hydrated—CO ONa is greater, whilst the hydrated... 

In the group with positive spreading coefficients (e.g., toluene-in-water and oleic acid-in-water emulsions), the values ofkj a in both stirred tanks and bubble columns decrease upon the addition of a very small amount of oil, and then increase with increasing oil fraction. In such systems, the oils tend to spread over the gas-liquid interface as thin films, providing additional mass transfer resistance and consequently lower k values. Any increase in value upon the further addition of oils could be explained by an increased specific interfacial area a due to a lowered surface tension and consequent smaller bubble sizes. 

A few studies have reported the embedding of an MIP film between two membranes as a strategy for the construction of composite membranes. For example, a metal ion-selective membrane composed of a Zn(II)-imprinted film between two layers of a porous support material was reported [253]. The imprinted membrane was prepared by surface water-in-oil emulsion polymerisation of divinylbenzene as polymer matrix with 1,12-dodecanediol-0,0 -diphenylphosphonic acid as functional host molecule for Zn(II) binding in the presence of acrylonitrile-butadiene rubber as reinforcing material and L-glutamic acid dioleylester ribitol as emulsion stabiliser. By using the acrylonitrile-butadiene rubber in the polymer matrix and the porous support PTFE, an improvement of the flexibility and the mechanical strength has been obtained for this membrane. 

FIGURE 37.1 Effect of moisturizer treatment on sodium hydroxide erosion time of xerotic leg skin, (a) Marked improvement of alkali resistance after treatment with a water-in-oil emulsion for four weeks (p <. 0001). (b) Slight but significant improvement after treatment with a lotion containing 12% lactic acid (p <. 01). Erosion assays were performed before and after treatment on four adjacent spots per leg. Data shown as box plots. Statistical analysis was performed with the paired Mest. 

Immunoglobulins are prone to loss of their bioactivity through proteolysis and heating. The encapsulation of immrmoglobulin Y obtained from egg yolk in a multiple oil-in water-in-oil emulsion was shown to be stable to pepsin and acid and more stable to heat treatment (95°C for 10 min) than the nonencapsulated form (Cho et al. 2005). 

Emulsification with caustic is possible with oils that have a fairly high total acid number (TAN). Below about 1.5 mg KOH/gm oil, the oils either will not emulsify or will form water-in-oil emulsions. The rate of emulsification with caustic is much faster than emulsification with surfactant mixtures, which is a characteristic property for emulsions generated via the agent-in-oil procedure (1 ). 

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