Study On Interaction Between Surfactants And Grafted Associating Acrylamide-Based Copolymer

The interaction between five surfactants with different molecular structures and a grafted associating acrylamide–based copolymer(PAAV) was studied in this paper. The five typical surfactants were surfactant sodium dodecyl sulfate (SDS),sodium dodecyl benzene sulfonate (SDBS),cetyltrimethylammonium bromide (CTAB),alkyl poly (ethylene 10) ether (OP-10) and dodecyl dimethyl amine B lactone (BS-12),respectively. The effects of temperature,salt concentration,shear rate and copolymer concentration on apparent viscosity of solution, and the effects of copolymer concentration on surface tension and interfacial tension of the compound with salt in the solution were studied, the results showed that the polymer PAAV had good thickening properties,salt tolerance,heat resistance,and amphipathy because of the strong association of molecule. What's more, the writer studied the influence law of the solution tackification performance with five different surfactants concentrations in pure water and brine solution and got the best concentration of compound of each surfactant and grafted associating copolymer. The flow law and the pH influence law of polymer and surfactant system in pure water were researched and got. By studying the influence law of surface tension and interfacial tension with different surfactant concentrations, we revealled the interaction mechanism between grafted associating copolymer and each surfactant.PAAV showed better thickening ability and salt-thickening effect behavior twice in a wide range of NaCl concentration. In the 5000 mg/L NaCl salt solution, 0.20 g/dL PAAV solution viscosity was 693.9 mPa·s; When the NaCl concentration was 30000 mg/L and 90000 mg/L, the solution viscosity was 265.9 mPa·s and 193 mPa·s,respectively in the range of 20 ~ 80℃. 0.20 g / dL PAAV due to the strong intermolecular association showed good heat resistance and thermal thickening behavior twice in the 5000 mg/L NaCl solution, and the highest viscosity of the solution was 889.8 mPa·s at 25℃; After more than 45℃, viscosity decreased slowly with increasing temperature, even at 80℃, viscosity of copolymer brine solution was still up to 510.9 mPa·s.The apparent viscosity of the 0.2 g/dL PAAV polymer increased rapidly and then decreased, and tended to balance lastly by addition of SDS,SDBS,CTAB in pure water and salt solution. The apparent viscosities of the solution were extremely 3443 mPa·s,3521 mPa·s and 2879 mPa·s in pure water, respectively, then the best thickening concentrations were 2 mmol/L, 0.8 mmol/L and 0.5 mmol/L, respectively.The solution viscosities were 869.3 mPa·s,905.1 mPa·s and 1107.8 mPa·s, and the best thickening concentrations were 1 mmol/L,0.3 mmol/L and 0.3 mmol/L in the 5000 mg/L NaCl brine solution, respectively. The polymer apparent viscosity increased firstly and then tended to balance with the increasing of BS-12 concentration. When BS-12 concentration was 1 mmol/L, the apparent viscosity of 0.2 g/dL PAAV pure water was 1036 mPa·s, The apparent viscosity of brine solution decreased to 753.5 mPa·s at the same BS-12 concentration. The apparent viscosity of the polymer solution drastically reduced, and then tended to a stable figure with increasing the concentration of OP-10; when OP-10 concentration was 1 mmol/L, the apparent viscosity in pure solution was 84 mPa·s. the apparent viscosity in brine solution was 12 mPa·s at the same OP-10 concentration. The results showed that the thickening ability of OP-10 was the weakest. The thickening ability of the composite solution by addition of SDBS was greater, but the thickening ability as the increasing of CTAB was stronger in salt water.The influence law of the apparent viscosity in complex solution of different pH showed: For the composite solution by addition of SDS or SDBS, the pH value lowered and the solution viscosity decreased with the adding of hydrochloric acid in pure water solution; when the pH value was 7 to 9 as the induction of alkali the viscosity decreased.With the induction of hydrochloric acid, the viscosity of the solution increased firstly and then decreased according to the lower of pH value in brine solution; when the pH value was 7 to 9 as the induction of alkali the, the viscosity decreased. The apparent viscosity of composite solution in pure water solution by addition of CTAB had the same change trend with SDS. The pH value lowered and the solution viscosity decreased with the adding of hydrochloric acid in brine solution; when the pH value was 7 to 9 as the induction of alkali the, the viscosity decreased. With increasing concentration of surfactant, the surface tension and interfacial tension of 0.01 g/dL PAAV solution in 5000 mg/L NaCl brine solution first rapidly reduced,when the concentration of SDS,SDBS,CTAB,OP-10,BS-12 respectively were 8 mmol/L,1.2 mmol/L,0.8 mmol/L,0.08 mmol/L and 7 mmol/L, and then tended to a stable minimum, the corresponding lowest surface tension values were 28.2 mN/m,26.2 mN/m,25.2 mN/m,37.4 mN/m,29.2 mN/m, and the corresponding values for minimum interfacial tension were 1.01 mN/m,0.07 mN/m,0.011 mN/m,0.11 mN/m,4×10-4mN/m, respectively.PAAV brine solution had good surface and interface activity. with the increase of polymer concentration, the Surface and interfacial tension of PAAV solution rapidly reduced and then all tended to stable, Separately for 29.2 mN/m and 3.5 mN/m when the concentration of polymer exceeded 0.04 g/dL. On the certain concentration of surfactant conditions, the Surface and interfacial tension reduced quickly with the increase of composite solution polymer PAAV concentration in 5000 mg/L NaCl brine solution. Then all tended to stability and were lower than those of polymer solution. When the concentration of SDS,SDBS,CTAB,OP-10,BS-12 were 1 mmol/L, 0.3 mmol/L, 0.3 mmol/L, 0.03 mmol/L and 1 mmol/L, the corresponding minimum surface tension value are were respectively 27.1 mN/m,24.1 mN/m,22.5 mN/m,28.4 mN/m and 26.4 mN/m;and minimum interfacial tension were respectively 0.75 mN/m,0.42 mN/m,0.076 mN/m,0.57 mN/m and 0.38 mN/m after PAAV reached a certain concentration in composite brine solution. These results showed that, varying degrees of interaction occurred between five kinds of surfactants and copolymer PAAV. The strongest effect between PAAV and CTAB, could significantly reduce the surface and interfacial tension, the second were SDBS and BS -12, BS-12 could well reduced solution interfacial tension. However, as the molecule structure of CTAB and BS-12 contained cation, precipitation and phase separation all easily emerged during the polymer flooding process, which was disadvantageous to application research of Polymer and surfactants system. So, SDBS, due to the better overall performance, was choosed for polymer flooding systems of polymer and surfactant.