Sulfonates, surfactant flood systems

Effect of Ca2. In many reservoirs the connate waters ontain substantial quantities of divalent ions (mostly Ca . In alkaline flooding applications at low temperatures, the presence of divalent ions leads to a drastic increase in tensions r35,36]. Kumar et al. f371 also found that Ca and Mg ions are detrimental to the interfacial tensions of sulfonate surfactant systems. Detailed studies at elevated temperatures appear to be non-existent. 

It was observed that the formulations consisting of ethoxylated sulfonates and petroleum sulfonates are relatively insensitive to divalent cations. The results show that a minimum in coalescence rate, interfacial tension, surfactant loss, apparent viscosity and a maximum in oil recovery are observed at the optimal salinity of the system. The flattening rate of an oil drop in a surfactant formulation increases strikingly in the presence of alcohol. It appears that the addition of alcohol promotes the mass transfer of surfactant from the aqueous phase to the interface. The addition of alcohol also promotes the coalescence of oil drops, presumably due to a decrease in the interfacial viscosity. Some novel concepts such as surfactant-polymer incompatibility, injection of an oil bank and demulsification to promote oil recovery have been discussed for surfactant flooding processes. 

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. 

H.S. Hanna and P. Somasundaran, "Physico-Chemical Aspects of Adsorption at Solid/Liquid Interfaces, Part II. Berea Sandstond/Mahogony Sulfonate System", in Improved Oil Recovery by Surfactants and Polymer Flooding, D.O. Shah and R.S. Schecter, eds.. Academic Press, 1977, p. 253-274. 

FIGURE 9.3 Interfacial tensions and solubilization parameters for microemulsions in a system containing a synthetic petroleum sulfonate, an alcohol cosurfactant, a mixture of refined oils, and NaCl brine. (From Reed, R.L. and Healy, R.N., in Improved Oil Recovery by Surfactant and Polymer Flooding, Shah, D.O. and Schechter, R.S., Eds., Academic Press, New York, 1977. With permission.)... 

The large supply of tall oils and the well-known surface properties of many of the components have led to several suggestions to use them or their derivatives in micellar flooding (X58.5 9.). However, there are, so far as we know, no extensive laboratory investigations underway nor plans to test these possibilities in the field. In view of the contribution tall oils might make to enhanced recovery if they could be used, a survey of interfacial tension properties of aqueous/hydrocarbon systems, similar to those which have become common with the petroleum sulfonate and other surfactants under consideration for micellar floods, seemed worthwhile. 

The equilibrated and nonequilibrated oil/brine/surfactant systems differed in their oil displacement efficiency. The equilibrated oil rather than the equilibrated aqueous phase of the surfactant solution is responsible for the high oil displacement efficiency of dilute surfactant systems containing no alcohol. The oil soluble fraction of petroleum sulfonate is more effective in lowering the interfacial tension and in promoting the flattening of oil drops. Almost 94% oil recovery was achieved in sandpacks by a low concentration ( 0.1%) surfactant plus alcohol formulation when used in place of brine flooding. 

A more recent study [70] examined the effects of the polymer on surfactant adsorption in a low tension polymer water flood (LTPWF). The surfactant was alkylpropoxyethoxy sulfate, Ci2-i5-(PO)4-(EO)2-0S03 Na, and the polymers were xanthan and a copolymer of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate (AN 125 from Floerger). The solid materials were sandstone cores from a North Sea oil reservoir, Berea, and Bentheim cores. For these systems the xanthan caused a 20% reduction in the adsorption of the surfactant. It was also observed that surfactant adsorption appeared to increase as the water... 

The propoxy ethoxy sulfonate used by Taugbpl et al. [14] also showed an IFT value close to 10 mN/m towards n-heptane in seawater. Figure 7. Thus, the present PO-EO-surfactant systems are able to lower the IFT between water and oil by a factor of more than three magnitudes in a Type II( —) phase behavior. The corresponding increase in the capillary number suggests that a significant amount of waterflooded residual oil will be recovered by a chemical flood performed in the two-phase region. 

Dual surfaetant systems, ethoxylated sulfonate/sulfate and alkane/ aromatie sulfonate, as potential flooding ehemicals have been studied in the laboratory by Miller et al. [3S] and in the field by Holley and Caylas [37]. In a laboratory experiment at low surfactant concentration, the residual oil saturation decreased to about 5% with increasing surfactant... 

Recently, Wellington and Richardson [J5] presented an interesting paper discussing the mechanism of low surfactant concentration enhanced water flood. The surfactant system consisted of alkyl-PO-EO glyceryl sulfonate with small amounts of an ethoxylated cationic surfactant to control phase behavior, interfacial activity, and surfactant loss. The surfactant systems had the ability to reduce their cloud point and interfacial tension when diluted, which was regarded as very useful for an effective flood performance. A surfactant concentration of about 0.4% removed essentially all the residual oil from sand packs in just over f PV with a surfactant loss of less than O.f PV. Mobility control by polymer was strongly required for good displacement and sweep efficiency and to reduce surfactant loss. 

---