Crude petroleum sulfonate system

This paper presents observations on the difference in behavior of emulsification processes which can occur during surfactant and caustic flooding in enhanced recovery of petroleum. Cinephotomicrographic observations on emulsion characteristics generated at the California crude oil-alkaline solution interface as well as in the Illinois crude oil-petroleum sulfonate system are reported. The interdroplet coalescence behavior of oil-water emulsion systems appear to be quite different in enhanced oil recovery processes employing various alkaline agents as opposed to surfactant/polymer systems. 

The interfacial tension behavior between a crude oil (as opposed to pure hydrocarbon) and an aqueous surfactant phase as a function of temperature has not been extensively studied. Burkowsky and Marx T181 observed interfacial tension minima at temperatures between 50 and 80°C for crude oils with some surfactant formulations, whereas interfacial tensions for other formulations were not affected by temperature changes. Handy et al. [191 observed little or no temperature dependence (25-180°C) for interfacial tensions between California crude and aqueous petroleum sulfonate surfactants at various NaCI concentrations. In contrast, for a pure hydrocarbon or mineral oil and the same surfactant systems, an abrupt decrease in interfacial tension was observed at temperatures in excess of 120°C 1 20]. Non ionic surfactants showed sharp minima of interfacial tension for crude... 

In this paper we report first the spontaneous emulsification mechanisms in the petroleum sulfonate and caustic systems. This is followed by the kinetics of coalescence in alkaline systems for both the Thums Long Beach (heavy) crude oil and the Huntington Beach (less viscous) crude oil. Measurements of interfacial viscosity, interfacial tension, interfacial charge and micellar aggregate distributions are presented. Interrelationships between these properties and coalescence rates have been established. 

FIG. 11 Film capacitance of crude oil/EOR system as a function of time the third kind of mechanisms of film rupture. Oil phase 30% Shengli crude oil/ -Cio aqueous phase 0.0025 mol/L NaOH + 0.02% petroleum sulfonate (PS). 

TABLE 7 Effect of Petroleum Sulfonate (LH) on Film Lifetimes in 30% Crude Oil/Alkali Systems... 

In a petroleum sulfonate/isobutanol/dodecane/brine system, there are two regions of ultralow interfacial tension (IFT), one at low surfactant concentrations (0.1-0.2%) and the other at higher surfactant concentrations (4 to 10%). In the low concentration range, the oil/brine/surfactant/alcohol system is a two-phase system, whereas at high surfactant concentrations, it becomes a three-phase system in which a middle phase microemulsion is in equilibrium with excess brine and oil. For low surfactant concentration systems, we have shown that the ultralow IFT minimum corresponds to the onset of micellization and partition coefficient of surfactant near unity. This correlation was observed for the effect of surfactant concentration, salt concentration and oil chain length on the interfacial tension. The minimum in interfacial tension corresponds to a maximum electrophoretic mobility of oil droplets. This correlation was also observed for the effect of caustic on several crude oils. 

This paper discusses the solution properties of the various alkaline chemicals which are important in chemical flooding systems. Data on the comparative efficiencies of highly alkaline sodium silicate solutions and sodium hydroxide solutions in recovering a heavy California crude oil from Berea sandstone cores by alkaline water-flooding are presented. A study on the use of various alkaline chemicals as a preflush for the removal of hardness ions from reservoir brine in Berea sandstone cores was made, and part of these findings are presented. Finally, some preliminary results on the increased recovery obtained with combinations of petroleum sulfonates and less-alkaline sodium silicates are given. 

Table 7. Silicate-Surfactant System for Oil Recovery SILICATE - 3.22 Ratio SiO /Na O, Sodium Silicate, PQ Corporation SURFACTANT - Stepan PETROSTEP" 420 Petroleum Sulfonate OIL - Kansas Crude, 34.5° API Gravity...

Table 1 shows the effect of the addition of isobutanol on various properties of oil/brine/surfactant systems for TRS 10-410 and TRS 10-80. Because the same IFT values were obtained for the systems with and without IBA (Table 1), the observed differences in oil recovery cannot be explained in terms of any change in IFT. The presence of alcohol did not significantly influence the partition coefficient of surfactant in n-dodecane or n-octane. It is important to emphasize that the partition coefficient changes sharply near the ultralow IFT region (19). Thus, the partition coefficient does not appear to correlate with the oil displacement efficiency. However, the presence of isobutanol decreases the interfacial viscosity and markedly influences the flattening time of the oil droplets. It has been suggested (18) that a rigid potassium oleate film at the oil/water interface can be liquefied by the penetration of the hexanol molecules in order to produce spherical microemulsion droplets. It has been shown (14) also that for a commercial petroleum sulfonate-crude oil system, the oil droplets with the alcohol coalesce much faster than the ones without alcohol. For the systems studied here, IBA is believed to have penetrated the petroleum sulfonate film as seen by the decrease in IFV. The decrease in interfacial viscosity would presumably promote the coalescence in porous media. 

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