Interaction between Bohai heavy oil components and petroleum sulfonate for lowering interfacial tension

Molecular composition of Bohai heavy oil components was investigated by element analysis and high-resolution mass spectrometry. Moreover, partition coefficient and interfacial tension (IFT) in petroleum sulfonate (PS) solution/model oil system were measured in order to elucidate the oil components- PS interaction responsible for low IFT. The results demonstrate that, as the mass fraction of asphaltene model oil increases, the partition coefficients of PS increase steeply after a slow increase period. When the mass fraction reaches 1%, IFT in the range of 10(-2 )mN center dot m(-1) is obtained at PS concentration as low as 500 mg center dot L-1. Due to high interfacial activity of asphaltene and its strong interactions with PS, more PS molecules are attracted to interface; meanwhile, the electrostatic repulsion between PS molecules at the interface is weakened by the inserted asphaltene molecules, which are the contributing mechanism for synergism for lowering IFT. However, with the concentration of resin or remaining fraction increasing, the partition coefficient of PS decreases and the equilibrium IFT increases firstly. It is because the adsorption of resin or remaining fraction which replaces PS molecules at the interface causes loose arrangement of interfacial active materials and increasing IFT, displaying antagonism.