Effect Of Nano-SiO₂/SDS On The Stability Of Foam With Oil By Molecular Dynamics Simulation

Foam is usually in the unstable state from the thermodynamics and dynamics viewpoint,so the stability of foam is a key problem to be solved urgently in foam flooding.Nano-SiO₂ as a new type of foam stabilizer has been favored by researchers for its unique advantages.At present,more extensive experimental studies have been carried out on stabilizing foam by nano-SiO₂,and it was found that it can greatly enhance the stability of foam.But it is difficult to give a reasonable explanation on the mechanisms by experimental results.Therefore,molecular dynamics simulations has been used to investigate the influence of the concentration of nano-SiO₂ and surfactant SDS on the stability of foam system.At the same time,the microscopic mechanism of its influence on the stability of foam containing oil was explored through dynamic process,molecular configuration and interaction between molecules at the molecular and atomic level.The results of the effect of single SDS on the stability of foam showed that when the gas-liquid interface only contains high concentration surfactants?36 and 25 SDS?,the hydrophobic interaction between the hydrophobic chain of the surfactant and oil is weak,and the electrostatic repulsion between the head of emulsifier and the head of surfactant in gas-liquid interface is strong,which means that the emulsified oil located in the liquid phase without moving to the gas-liquid interface.When the gas-liquid interface only contains medium?16 SDS?and low?9SDS?concentration surfactants,the hydrophobic interaction between the hydrophobic chain of the surfactant and oil is strong,and the electrostatic repulsion between the head of emulsifier and the head of surfactant in gas-liquid interface is weak,which means that the emulsified oil tended to move to the gas-liquid interface and enter it.The results of the effect of nano-SiO₂/SDS on the stability of foam showed that the stability of the foam varies with the number of SiO₂ as for the system with different concentrations of surfactant SDS in gas-liquid interface.When the gas-liquid interface contains medium?16 SDS?concentration surfactants,the stability of the foam changed from unstable to stable and finally became unstable with the increase of the number of SiO₂,which means that appropriate concentration of SiO₂ could stabilize the foam under such conditions.When the gas-liquid interface contains low?9 SDS?concentration surfactants,the foam has been in a state of instability with the increasing of the number of SiO₂,which means that SiO₂ could not effectively stabilize the foam under this condition.When the gas-liquid interface contains high?36 and 25 SDS?concentration surfactants,the stability of the foam changed from stable to unstable with the increasing of the number of SiO₂,which means that high concentration of SiO₂ could not stabilize the foam under such conditions.