Reduetion of surfactant retention by using polyphosphates as chelating agent in micellar flooding is discussed in this paper.
Laboratory flooding tests have been performed in simulated sandpacks which consisted of kaolinte and quartz, with petroleum sulfonate TRS 10 - 80 dissolved in brines with different sodium (or calcium) concentrations. Micellar slug flooding with or without polyphosphate preflush was compared. Other experiments concerning the influences of polyphosphates on surfactant solubility in calcium brines,the exchangeable cations on clay surface, etc. were also performed.
The main conclusions are: 1)in a calcium brine environment, the loss of surfactant can be reduced significantly by the addition of polyphosphates to both preflush and micellar slug,but in a sodium brine environment, its effectiveness is somewhat poor; and 2) polyphosphates improve the surfactant solubility in calcium brine and enhance the exchange of cations between solid and liquid. These behaviors can be explained by the chelation of polyphosphate with calcium and its effect on the surface potential of clay particles. Based on the experimental results, it is concluded that polyphosphates are potential additives in surfactant flooding.