Alkali-surfactant-polymer recovery

Alkali/polymer flooding Alkali/surfactant/polymer flooding Alkaline-assisted thermal oil recovery Alkaline steamflooding Polymer-assisted surfactant flooding Water-alternating gas technology... 

Figure 6. Comparison of Oil Recoveries for Various Slug Sizes of Alkali/Surfactant/Polymer...

Figure 7. Comparison of Oil Recoveries (at 5% oil cut) for Various Alkali/Surfactant/Polymer Slug Sizes...

Cmc values are important in virtually all of the petroleum industry surfactant applications. For example, a number of improved or enhanced oil recovery processes involve the use of surfactants including micellar, alkali/surfactant/polymer (A/S/P) and gas (hydrocarbon, N2, CO2 or steam) flooding. In these processes, surfactant must usually be present at a concentration higher than the cmc because the greatest effect of the surfactant, whether in interfacial tension lowering [30] or in promoting foam stability [3J], is achieved when a significant concentration of micelles is present. The cmc is also of interest because at concentrations... 

Recent laboratory studies have demonstrated the potential utility of borates as alkaline agents in chemical enhanced oil recovery. Compared with existing alkalis, sodium metaborate has an unusually high tolerance toward the hardness ions, Ca + and Mg +, paving the way for the implementation of alkali-surfactant-polymer floods for the large number of high-hardness saline carbonate reservoirs. In the absence of surfactants, borate solutions exhibit a strong tendency for spontaneous imbibition, or uptake into oil-wet or mixed-wet carbonate cores, with consequently improved recovery of oil compared with solutions of other salts and alkalis. 

In these three schemes, the amount of alkali or polymer was the same. Only the injected surfactant was gradually reduced. In these schemes, it was observed that the incremental oil recovery factors over waterflooding were almost the same. Because less surfactant was injected in Schemes 2 and 3, Schemes 2 and 3 were economically more attractive than Scheme 1. 

A new technique using C02-activated plugs of sodium orthosilicate is used to plug fractures in sandstone cores. This is followed by injection of chemical slugs, such as alkali/surfactant and polymer/alkali/surfactant. A series of experimental runs were conducted on artificially fractured Berea sandstone cores. It is shown that recovery as high as 75% of the oil In place is possible with the novel treatment as compared to less than 10% recovery with waterfloods. Results are presented for various slug sizes. 

Nasr-El-Din, H. A. and B. F. Hawkins, Recovery of Residual Oil Using Alkali, Surfactant and Polymer Slugs in Radial Cores, Revue de I lnstitut Frangais du Petrole 46, 199-219 (1991). 

The borate formulation was not previously optimized using phase behavior or oil/water i.f.t. screening tests and yet still performed reasonably well in terms of tertiary oil recovery, chemical (strong alkali, surfactant, and polymer) loss, and in addition no injectivity problems were encountered. 

The effectiveness of alkaline additives tends to increase with increasing pH. However, for most reservoirs, the reaction of the alkaline additives with minerals is a serious problem for strong alkalis, and a flood needs to be operated at the lowest effective pH, approximately 10. The ideal process by which alkaline agents reduce losses of surfactants and polymers in oil recovery by chemical injection has been detailed in the literature [1126]. 

Surfactants are used extensively in enhanced oil recovery. Applications include micellar floods or flooding in conjunction with polymers, alkalis, steam or carbon dioxide. Another apphcation is the generation of foams for mobility control or blocking and diverting. For each of these applications care must be taken in selecting the surfactants. Surfactants tend to be a major portion of the costs associated with FOR, and losing surfactant to adsorption leads to substantial economic losses. 

Based on these fundamental results the filler flotation from different types of waste paper was investigated. The flotation experiments were conducted in tap water (286 ppm CaCOj) using the standard deinking formulation. Besides alkali this formulation contain hydrogen peroxide and sodium silicate, which increases the selectivity and has been proven to be a dispersant for fillers [4]. 0.2% of the anionic surfactant or of the cationic polymer was applied. The results are summarized in Fig. 10 and are given as percent ash (filler) content in the flotated pulp. A low ash content means a high recovery of the fillers. 

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