Surface oil

Oil reservoirs are layers of porous sandstone or carbonate rock, usually sedimentary. Impermeable rock layers, usually shales, and faults trap the oil in the reservoir. The oil exists in microscopic pores in rock. Various gases and water also occupy rock pores and are often in contact with the oil. These pores are intercoimected with a compHcated network of microscopic flow channels. The weight of ovedaying rock layers places these duids under pressure. When a well penetrates the rock formation, this pressure drives the duids into the wellbore. The dow channel size, wettabiUty of dow channel rock surfaces, oil viscosity, and other properties of the cmde oil determine the rate of this primary oil production. 

The other problem that can occur with metals is the presence of various machine oils on the surface, such as might be used in the automotive area. Oil serves as a low surface energy barrier to adhesion, in most instances. Abrading and solvent wipe are recommended or else degreasing. Removing the surface oil is... 

Adsorption of corrosion inhibitors or cationic surfactants can reduce sandstone formation permeability. Alcohols can be used to remove corrosion inhibitors from rock surfaces. Oil-soluble corrosion inhibitors may be dissolved by organic solvents such as xylene or toluene containing a mutual solvent, most often ethylene glycol monobutyl ether, EGMBE (167). Aqueous fluids containing 5-10% EGMBE can be used to dissolve cationic surfactants. 

Significant releases of petroleum hydrocarbons from unlined surface impoundments in oil fields have also been reported as far back as the early 1900s. One unlined surface oil reservoir located in the Kem River field, southern California, had a reported fluid loss on the order of 500,000 barrels. Excavated pits showed oil penetration to depths exceeding 20 ft. Another loss of 1 million barrels over a period of 6 years occurred from another unlined reservoir in the same field, although some of this loss was through evaporation. 

Baildown testing is a widely used field method to evaluate the actual thickness of LNAPL product in a monitoring well. Baildown testing involves the rapid removal of fluids from the well, and subsequent monitoring of fluid levels, both the water level or potentiometric surface (oil-water interface) and NAPL level (oil-air interface), with time. Such testing was originally used as a preliminary field method to evaluate recoverability of NAPLs and thus to determine potential locations for recovery wells. All monitoring wells at a site that exhibited a measurable thickness of LNAPL were typically tested. Whether or not all the LNAPL product could be... 

Composition of Surface Film and Adhesion of UVC Lacquer. As the deadhesion of UVC lacquer has occurred at the interface between the substrate and lacquer (or in the oil film), both chromium oxide and oil film affect the adhesion performance. From this standpoint, the adhesion of the UVC lacquer is summarized in Fig. 9. When chromium oxide is hydrated to a high degree or surface oil is oxidized to a greater level, the adhesion of the UVC lacquer does not deteriorate. 

Figure 8. Change of covering rate (a), n-value and the polar group ratio of surface oil with pretreatment...

Figure 11. Correlation of Yc the polar group of carbon of surface oil.

During prebaking for the internal coating, dehydration of chromium hydroxide (decrease in n-value) has occurred. If surface oil is oxidized at the same time, the adhesion loss of UVC lacquer due to the dehydration is made up for by the oxidation of the oil. 

Oil reduction in deep-fat-fried products may be obtained through prefrying and/or postfrying treatments. Prefrying treatments are mainly based on the marked effect that the crust microstructure has in oil absorption, and mainly intend to reduce surface permeability. Postfrying treatments aim to remove surface oil before postcooling suction begins. 

Figure 11.3 Kinetics of oil uptake fractions and total oil in potato slices during frying at (a) 1 20°C (b) 150°C (c) 180°C. TO total oil PSO penetrated surface oil SO surface oil STO structural oil (reprinted with permission fromj. Food Eng., 2008, 87, 200-212).

Scanning electron microscopy (SEM) is a powerful tool used to study the surface topography of potato chips. Figure 11.5 shows that potato chips lose a considerable quantity of surface oil after they are washed in petroleum ether, which allows clear observation of the cellular microstructure of the surface (Figures 11.5bl, 11.5b2 and 11.5b3) (Pedresehi etal., 2008). 

Analysis of Spray Dried Samples. Moisture content was determined in duplicate via toluene distillation and total volatile oil by Clevenger (l ). Surface oil was measured by Soxhlet extraction (2). Shelf-life was determined by gas chromatography (6) the end of shelf-life was the time taken (at 37 C storage) to reach a limonene epoxide concentration of 2 mg/g oil. 

If the oil is not properly encapsulated, it will be quickly oxidised. The quantity of surface oil may be determined by cold washing the powder with hexane. 

Emulsions made with a fine oil droplet particle size, usually less than one micron, are more stable with the oil droplets less likely to coalesce and separate. The encapsulation of a good quality emulsion is generally more efficient with less surface oil on the spray-dried powder. We wanted to build surfactant properties into the starch backbone to improve encapsulation efficiencies. Studies of the mechanism by which surfactants stabilize emulsions were made in order to accomplish this. 

A 10 gram sample was placed in a 200 ml round bottom flask and 100 ml of distilled water added. A Dean-Stark trap and condenser were used and the mixture was brought to a boil. The steam distilled oil was measured after four hours versus control mixtures. In order to measure surface oil on the spray-dried powders, the powder was first washed with a solvent (ethyl ether or hexane) then oil retentions were run by the steam distillation method illustrated above. Differences in oil volume for solvent washed versus non-washed were attributed to surface oil on the spray-dried powders. 

This is a subjective test to determine the storage stability of an emulsion. A sample of the liquid emulsion before spray-drying is used to fill a 16 oz. tall glass jar. The jar is capped and stored in an oven for 16 hours at 50 C. When storage is complete, the jar is removed from the oven and evaluated. Surface oil layers on the emulsion indicate poor emulsion stability performance by the carrier. 

Emulsions of lemon oil stabilized with gum arabic, a conventional starch dextrin and a low viscosity starch octenylsuccinate were spray-dried and evaluated for encapsulating efficiencies. Oil retentions and surface oil determinations were made according to the Materials and Methods section. TABLE 3 demonstrates the superiority of the starch octenylsuccinate in flavor retention and surface oil to gum arabic and a starch dextrin (5) ... 

In order to further demonstrate the superior encapsulation efficiencies of starch octenylsuccinates, comparison studies of surface oil versus oil level were made against gum arabic (2). The data is presented in TABLE 4 ... 

At lower oil usage levels (20% - 307o) gum arabic and starch octenylsuccinates performed equally. High oil levels (greater than 407o) showed marked differences in surface oil content of the powders, with the starch octenylsuccinates out performing gum arabic. Less flavor oil on the surface of the powder will help improve overall shelf-life stability. 

King, W., Trubiano, P., and Perry, P., Modified Starch Encapsulating Agents Offer Superior Emulsification, Film Forming and Low Surface Oil, Food Prod. Dev., 10, 54, 1976. 

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