Low interfacial tension nanofluid oil displacement agent and preparation and application thereof

The invention discloses a nano-fluid oil displacement agent with low interfacial tension as well as preparation and application of the nano-fluid oil displacement agent. The nano-fluid oil displacement agent is prepared from the following raw materials in parts by weight: 5 to 12 parts of amphiphilic SiO2 nano-particles, 10 to 20 parts of a nonionic surfactant, 10 to 30 parts of a diamine type benzoxazine surfactant, 0.05 to 3 parts of a dispersion phase and 35 to 65 parts of water, wherein the diamine type benzoxazine surfactant is prepared from the following raw materials in parts by weight: 20 to 40 parts of a p-hydroxybenzene compound, 20 to 30 parts of a diamine compound, 10 to 20 parts of paraformaldehyde and 10 to 20 parts of methylbenzene. The nano-fluid oil-displacing agent has the beneficial effects that the nano-fluid oil-displacing agent can be stably dispersed for more than 9 hours under the conditions of 120 DEG C and 6.0 * 10 < 4 > mg/L, and the interfacial tension is 10 -10 mN/m; th