Property evaluation of a new selective water shutoff agent for horizontal well

In this paper, emulsified asphalt, a new type of selective water shutoff agent for horizontal well was developed. The emulsifying effect of surfactants on asphalt, the influence of inorganic salt, temperature and surfactant stabilizer on the stability of emulsified asphalt, and the impact of core permeability and surfactant pre-flush fluid on the injection efficiency of emulsified asphalt were studied. Moreover, the effect of external conditions on the stability and injection efficiency of emulsified asphalt was analyzed from the point of the interfacial electrical property and interfacial viscosity. The results indicate that the oil–water interfacial tension (IFT) is relevant to the emulsifying ability of surfactant for asphalt, and the emulsifying ability is improved as the IFT decreases. However, there is no relationship between the IFT and the stability of emulsified asphalt. The Zeta potential of emulsified oil droplet and emulsion stability at normal temperature is well related under the influence of inorganic salt, and the emulsion stability becomes better as the absolute value of Zeta potential increases. Under the influence of temperature, Zeta potential turns to have nothing to do with the stability of emulsified asphalt, while the oil–water interfacial viscosity gets to be the main affecting factor on it, that is, high interfacial viscosity is beneficial to the emulsion stability. Surfactant additives can enhance the emulsion stability through regulating the Zeta potential, and the surfactant pre-flush fluid can improve the injection efficiency of emulsified asphalt by increasing its stability. The above results can be used as guidance in the formulation design and mechanisms studies of emulsified asphalt for selective water shutoff for horizontal well.