Study On Foam Stabilization Law And Mechanism Of Gemini Surfactant 12-s-12/DTAB Compound System

Enhancing rate of oil recovery has become a significant research project because of the energy shortage,while foam flooding is one of the effective tertiary oil recovery methods,and a good foam system can increase recovery efficiency by more than 20% compared with traditional water flooding one.The surfactant affects the stability of the foam system directly.In this paper,Gemini surfactants with double chains(12-s-12)and a single chain surfactant dodecyl trimethyl ammonium bromide(DTAB)were used to form different complex systems.And the foam properties of the complex systems were investigated by means of experimental method and molecular dynamics simulation,respectively.The foam stability regulation was studied,and the mechanism of foam stabilization was discussed from molecular level.The reaction conditions of 12-6-12 were briefly investigated,and four kinds of Gemini surfactants 12-6-12(s=4,6,8,10)were synthesized.12-6-12,12-10-12 and DTAB were mixed according to the ratio of 12-s-12/DTAB 0.05,0.1 and 0.2 respectively.The foam properties and apparent morphology of the complex systems were investigated by JPM2012 A automatic foam analyzer and metallographic microscope,respectively.It was found that when the same Gemini surfactant was mixed with DTAB,the foam stability and liquid carrying capacity increased with increasing of the compound ratio,and the apparent morphology changed significantly.When the ratio of 12-s-12/DTAB equals 0.1,the foam has good application effect,which can significantly reduce the amount of 12-s-12 in industrial application.In the same proportion,the foam property of 12-6-12 composite system is better than that of the 12-10-12 system.Based on the above research,12-s-12(s=2,6,10)/DTAB with adding 12-2-12 were selected to investigate using coarse-grained simulation method,and a gas-liquid interface model with oil droplet behavior as the index was established.The ratio of 12-s-12/DTAB was determined to be 0.1(s=2,6,10)according to the pre-simple simulation.And the simulation and experimental results were in good agreement.The foam stabilization mechanism of 12-6-12/DTAB systems was analyzed in terms of the interfacial formation energy,equilibrium configuration properties of interfacial monolayer and interaction between surfactant and water.The effect of linking groups of Gemini surfactant on the properties of foam was analyzed from the microscopic level.When the length of the linking group was moderate(s=6),the electrostatic repulsion force between the charged head groups was reduced,which made the molecules more tightly arranged at the gas liquid interface to enhance the binding of water molecules and the foam properties.While the length of the linking group was too long(s=10),the degree of branching of the molecules is too high,and steric hindrance affects the tight arrangement of surfactant molecules on the interface,which is unfavorable to form a thick liquid film.In this paper,the foam properties of Gemini surfactants compound systems were investigated combining experiments and molecular dynamics simulation methods,which was helpful for the application of Gemini surfactants in foam respect.