Surfactant for oil displacement, synthetic method and application of surfactant in oil displacement system

The invention belongs to the field of chemical oil displacement for improving the crude oil recovery ratio, and particularly relates to synthesis of a surfactant for oil displacement and application of the surfactant in an oil displacement system. Fatty acid, naphthenic acid, tall oil fatty acid and organic amine which are wide in raw material source are taken, and are subjected to acylation reaction, etherification reaction and carboxylation reaction to synthesize the nonionic-to-anionic surfactant. The molecular structure of the surfactant is clear, the lipophilic group is aliphatic hydrocarbon or cycloalkane and is connected with the hydrophilic group and the carboxyl group through an amido polyoxypropylene ether chain, and the balance of the lipophilic capacity and the hydrophilic capacity is adjustable. The non-anionic mixed surfactant is excellent in performance, and can exert good interfacial activity and excellent synergistic effect when being independently used in tertiary oil recovery or being compo