Preparation method of temperature-resistant and salt-tolerant nano oil displacement agent

The invention provides a preparation method of a temperature-resistant and salt-tolerant nano oil displacement agent. The preparation method comprises the following steps: modifying polyacrylamide to surfaces of silica nanoparticles through chemical bonds to obtain nano-composite particles with stable performance, and then using the nano-composite particles together with alkali and a surfactant to prepare the nano oil displacement agent. The nano oil displacement agent can solve the problem about high possibility of falling off of a polymer on the surface of a traditional nano oil displacement agent in the formation moving process, so as to achieve an excellent oil displacement effect. Especially in the high-temperature and high-salt formation, the nano oil displacement agent can overcome harsh formation conditions and cannot reduce the oil displacement effect.