Experimental Study of Salinity and Ionic Strength Effects on Critical Micelle Concentration of a Cationic Surfactant (HTAB)

The interfacial tension of surfactant solutions is decreased with increasing surfactant concentration to obtain the critical micelle concentration (CMC). After that, the CMC values does not alter much. So this concentration is a critical point during surfactant flooding that is one of the chemical EOR techniques. The reduction of the CMC value is taken into consideration, since the surfactant flooding is very expensive. The surfactant evaluated in this study is a cationic HTAB surfactant that is more appropriate for carbonated oil reservoirs. This research investigates the effect of four different salts (CaCl2, MgCl2, Na2SO4, and NaCl) at different concentrations (0, 0.1, 0.5, and 1 wt%) on the CMC value. All the experiments were conducted by surface tension technique to measure the CMC values. Also, the ionic strength was calculated for all solutions. Results imply that the addition of all of the salts reduced the CMC value and Na2SO4 had the best performance comprise the others. Increasing the salt concentration leads to declining the CMC value for NaCl, and for other salts this behavior was continued till 0.5 wt%. Then it is elevated. The cost consideration indicates addition of slats can reduce the amount of surfactant flooding const over 12 times.