715
film with the interface of the oil-water emulsion which leads to stability of the emulsion [37].
In the crude oil analysis, typically the total acid number (TAN) is measured,
which corresponds to the mass of KOH in milligrams necessary to neutralize the
acids contained in 1 g of oil. The acidity of crude oil can be attributed to the presence of naphthenic acids. The pK a value for naphthenic acids in crude oil was found
to be ~4.9, which depends upon the number of carbon chains and presence of one,
two, or three saturated rings [38].
2.2 Skin Formation
It is very often reported that the water-in-oil emulsion is stabilized by asphaltenes or
high molecular surface-active compound [39, 40]. Crude oil contains various natural surfactants such as high molecular weight surface-active compounds (asphaltenes
and resins) and low molecular surface-active compounds (sodium naphthenate, calcium naphthenate). Czarnecki and Moran [41] studied the contribution of low
molecular weight surface-active compounds such as sodium naphthenate (SN), etc.
Czarnecki and Moran [41] explained the competitive nature in making of a skin
(layer) on the oil-water interface in Fig. 4. Figure 4 shows that the high asphaltenic
(high molecular weight) compounds have lower surface activity and slow and irreversible rate, whereas surfactants such as sodium naphthenates are highly active and
have a fast adsorption rate.
Czarnecki and Moran [41] also studied the interfacial tension with respect to SN
concentration. With an increase in the concentration of SN, the surface and interfacial tension (γ) is reduced. At low concentration, SN makes a rigid interface, but at
higher concentration, the interface becomes flexible and shows a low interfacial
Fig. 4 Schematic of the model depicting the competition between subfractions of asphaltenes and
low molecular weight surfactants at the oil/water interface. (Copyright 2005 American Chemical
Society publishing. The figure is adapted with permission from ref. [41])
Stability and Destabilization of Water-in-Crude Oil Emulsion
film with the interface of the oil-water emulsion which leads to stability of the emulsion [37].
In the crude oil analysis, typically the total acid number (TAN) is measured,
which corresponds to the mass of KOH in milligrams necessary to neutralize the
acids contained in 1 g of oil. The acidity of crude oil can be attributed to the presence of naphthenic acids. The pK a value for naphthenic acids in crude oil was found
to be ~4.9, which depends upon the number of carbon chains and presence of one,
two, or three saturated rings [38].
2.2 Skin Formation
It is very often reported that the water-in-oil emulsion is stabilized by asphaltenes or
high molecular surface-active compound [39, 40]. Crude oil contains various natural surfactants such as high molecular weight surface-active compounds (asphaltenes
and resins) and low molecular surface-active compounds (sodium naphthenate, calcium naphthenate). Czarnecki and Moran [41] studied the contribution of low
molecular weight surface-active compounds such as sodium naphthenate (SN), etc.
Czarnecki and Moran [41] explained the competitive nature in making of a skin
(layer) on the oil-water interface in Fig. 4. Figure 4 shows that the high asphaltenic
(high molecular weight) compounds have lower surface activity and slow and irreversible rate, whereas surfactants such as sodium naphthenates are highly active and
have a fast adsorption rate.
Czarnecki and Moran [41] also studied the interfacial tension with respect to SN
concentration. With an increase in the concentration of SN, the surface and interfacial tension (γ) is reduced. At low concentration, SN makes a rigid interface, but at
higher concentration, the interface becomes flexible and shows a low interfacial
Fig. 4 Schematic of the model depicting the competition between subfractions of asphaltenes and
low molecular weight surfactants at the oil/water interface. (Copyright 2005 American Chemical
Society publishing. The figure is adapted with permission from ref. [41])
Stability and Destabilization of Water-in-Crude Oil Emulsion