Surfactant flooding dilute

Sometimes (especially in the past), surfactant flooding using low concentrations is called dilute surfactant flooding or simply surfactant flooding, whereas... 

In dilute surfactant flooding, oil droplets must be able to deform to pass through pore throats. In other words, the deformation capability of oil droplets in dilute surfactant flooding is very important. This effect can be achieved by low IFT. 

Recently we have carried out laboratory tests (17, 18, 19) in which the sodium silicate was added directly to a dilute surfactant solution to recover oil. Such a process would be akin to alkaline flooding processes where a dilute surfactant is formed in-situ. In this case however the crude is lighter and does not contain the natural acids necessary to form surfactants in-situ. Therefore surfactant is injected and protected or enhanced by the sodium silicate such that a low tension waterflood is assured. Such a system is less complex and therefore more widely applicable than micellar/polymer techniques thus filling the void between the alkaline and micellar/polymer EOR processes. 

Low tension waterflooding is a method intermediate between alkaline and micellar/polymer technology. The LTWF employs a dilute surfactant to reduce IFT and mobilize residual oil. A few field trials (26-29) of this process have been tried with mixed success. None of these trials however employed sodium silicates in any part of the flood design. Instead, other alkalis such as sodium carbonate and sodium tripoly- phosphate were used. Some of the reasons proposed for the limited success in these trials were 1) high consumption of the sacrificial agents, leaving the surfactant unprotected, 2) poor sweep of the pay zone, 3) limited mobility control and lower than expected displacement efficiency. Recent work published and obtained in our laboratories has shown that sodium silicates may help to overcome some of these problems better than other alkalis. 

It is interesting to note that the shape of the cumulative oil recovery curves in the unconsolidated sandpack is similar to that in the consolidated Berea core (Figures 1 and 9), except that oil is produced at a much faster rate for the sandpacks. Therefore, the oil displacement mechanism is presumably the same in these two porous media for the continuous dilute surfactant solution flooding process. Chou and Shah (22) have shown that 1 or 4 ft sandpacks give identical results for oil recovery and the fluid production... 

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. 

Surfactant-polymer flooding involves successive injections into the reservoir of an aqueous surfactant-cosurfactant solution and a dilute aqueous solution of a high molecular weight polymer. The primary purpose of the surfactant slug is to reduce the interfacial... 

For all these cases, the total amount of each chemical was the same. The core flood results are shown in Figure 13.21. We can see that the incremental oil recovery factors over waterflooding in Schemes 2 and 4 were obviously higher than that in Scheme 1. The alkali and surfactant concentration gradients from high to low can overcome the negative effects at the displacement front caused by dilution, alkali consumption, and surfactant adsorption. 

Because of the cost and the time factors involved, oil displacement studies are always preceded by certain test tube screening procedures. Specifically, the interfacial tension (IFT) of less than 0.01 dyne/cm is recognized to be the necessary but not the sufficient criterion for selection of a surfactant system. Many investigators (10-15) have shown that ultralow IFT of less than 0.001 dyne/cm can be achieved with less than 0.1 wt. % surfactant solution. Since this low surfactant concentration system is several hundred times more dilute than the ones used in a typical surfactant-polymer flooding process, the economics dictates that the oil displacement by such low surfactant concentration solution should be explored. Moreover, it should be established that the... 

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. 

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